path: root/doc/rfc/rfc5022.txt

Network Working Group                                        J. Van Dyke
Request for Comments: 5022                      Cantata Technology, Inc.
Obsoletes: 4722                                           E. Burger, Ed.
Category: Informational                                BEA Systems, Inc.
                                                              A. Spitzer
                                                         Bluesocket Inc.
                                                          September 2007


       Media Server Control Markup Language (MSCML) and Protocol

Status of This Memo

   This memo provides information for the Internet community.  It does
   not specify an Internet standard of any kind.  Distribution of this
   memo is unlimited.

IESG Note

   This RFC is not a candidate for any level of Internet Standard.  The
   IETF disclaims any knowledge of the fitness of this RFC for any
   purpose and in particular notes that the decision to publish is not
   based on IETF review for such things as security, congestion control,
   or inappropriate interaction with deployed protocols.  The RFC Editor
   has chosen to publish this document at its discretion.  Readers of
   this document should exercise caution in evaluating its value for
   implementation and deployment.  See RFC 3932 for more information.

Abstract

   Media Server Control Markup Language (MSCML) is a markup language
   used in conjunction with SIP to provide advanced conferencing and
   interactive voice response (IVR) functions.  MSCML presents an
   application-level control model, as opposed to device-level control
   models.  One use of this protocol is for communications between a
   conference focus and mixer in the IETF SIP Conferencing Framework.















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RFC 5022                         MSCML                    September 2007


Table of Contents

   1. Introduction ....................................................4
      1.1. Conventions Used in This Document ..........................5
   2. MSCML Approach ..................................................5
   3. Use of SIP Request Methods ......................................6
   4. MSCML Design ....................................................8
      4.1. Transaction Model ..........................................8
      4.2. XML Usage ..................................................9
           4.2.1. MSCML Time Values ...................................9
   5. Advanced Conferencing ..........................................10
      5.1. Conference Model ..........................................10
      5.2. Configure Conference Request <configure_conference> .......11
      5.3. Configure Leg Request <configure_leg> .....................13
      5.4. Terminating a Conference ..................................14
      5.5. Conference Manipulation ...................................15
      5.6. Video Conferencing ........................................16
      5.7. Conference Events .........................................17
      5.8. Conferencing with Personalized Mixes ......................18
           5.8.1. MSCML Elements and Attributes for
                  Personalized Mixes .................................19
           5.8.2. Example Usage of Personalized Mixes ................20
   6. Interactive Voice Response (IVR) ...............................23
      6.1. Specifying Prompt Content .................................24
           6.1.1. Use of the Prompt Element ..........................24
      6.2. Multimedia Processing for IVR .............................30
      6.3. Playing Announcements <play> ..............................31
      6.4. Prompt and Collect <playcollect> ..........................32
           6.4.1. Control of Digit Buffering and Barge-In ............33
           6.4.2. Mapping DTMF Keys to Special Functions .............33
           6.4.3. Collection Timers ..................................35
           6.4.4. Logging Caller DTMF Input ..........................36
           6.4.5. Specifying DTMF Grammars ...........................36
           6.4.6. Playcollect Response ...............................37
           6.4.7. Playcollect Example ................................38
      6.5. Prompt and Record <playrecord> ............................38
           6.5.1. Prompt Phase .......................................38
           6.5.2. Record Phase .......................................39
           6.5.3. Playrecord Example .................................41
      6.6. Stop Request <stop> .......................................42
   7. Call Leg Events ................................................43
      7.1. Keypress Events ...........................................43
           7.1.1. Keypress Subscription Examples .....................45
           7.1.2. Keypress Notification Examples .....................45
      7.2. Signal Events .............................................46
           7.2.1. Signal Event Examples ..............................47
   8. Managing Content <managecontent> ...............................48
      8.1. Managecontent Example .....................................50



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   9. Fax Processing .................................................51
      9.1. Recording a Fax <faxrecord> ...............................51
      9.2. Sending a Fax <faxplay> ...................................53
   10. MSCML Response Attributes and Elements ........................56
      10.1. Mechanism ................................................56
      10.2. Base <response> Attributes ...............................56
      10.3. Response Attributes and Elements for <configure_leg> .....57
      10.4. Response Attributes and Elements for <play> ..............57
            10.4.1. Reporting Content Retrieval Errors ...............58
      10.5. Response Attributes and Elements for <playcollect> .......59
      10.6. Response Attributes and Elements for <playrecord> ........60
      10.7. Response Attributes and Elements for <managecontent> .....61
      10.8. Response Attributes and Elements for <faxplay>
            and <faxrecord> ..........................................61
   11. Formal Syntax .................................................62
      11.1. Schema ...................................................62
   12. IANA Considerations ...........................................73
      12.1. IANA Registration of MIME Media Type application/
            mediaservercontrol+xml ...................................73
   13. Security Considerations .......................................74
   14. References ....................................................75
      14.1. Normative References .....................................75
      14.2. Informative References ...................................76
   Appendix A.  Regex Grammar Syntax .................................78
   Appendix B.  Contributors .........................................79
   Appendix C.  Acknowledgements .....................................79

























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RFC 5022                         MSCML                    September 2007


1.  Introduction

   This document describes the Media Server Control Markup Language
   (MSCML) and its usage.  It describes payloads that one can send to a
   media server using standard SIP INVITE and INFO methods and the
   capabilities these payloads implement.  RFC 4240 [2] describes media
   server SIP URI formats.

   Prior to MSCML, there was not a standard way to deliver SIP-based
   enhanced conferencing.  Basic SIP constructs, such as those described
   in RFC 4240 [2], serve simple n-way conferencing well.  The SIP URI
   provides a natural mechanism for identifying a specific SIP
   conference, while INVITE and BYE methods elegantly implement
   conference join and leave semantics.  However, enhanced conferencing
   applications also require features such as sizing and resizing, in-
   conference IVR operations (e.g., recording and playing participant
   names to the full conference), and conference event reporting.  MSCML
   payloads within standard SIP methods realize these features.

   The structure and approach of MSCML satisfy the requirements set out
   in RFC 4353 [10].  In particular, MSCML serves as the interface
   between the conference server or focus and a centralized conference
   mixer.  In this case, a media server has the role of the conference
   mixer.

   There are two broad classes of MSCML functionality.  The first class
   includes primitives for advanced conferencing, such as conference
   configuration, participant leg manipulation, and conference event
   reporting.  The second class comprises primitives for interactive
   voice response (IVR).  These include collecting DTMF digits and
   playing and recording multimedia content.

   MSCML fills the need for IVR and conference control with requests and
   responses over a SIP transport.  VoiceXML [11] fills the need for IVR
   with requests and responses over a HTTP transport.  This enables
   developers to use whatever model fits their needs best.

   In general, a media server offers services to SIP UACs, such as
   Application Servers, Feature Servers, and Media Gateway Controllers.
   See the IPCC Reference Architecture [12] for definitions of these
   terms.  It is unlikely, but not prohibited, for end-user SIP UACs to
   have a direct signaling relationship with a media server.  The term
   "client" is used in this document to refer generically to an entity
   that interacts with the media server using SIP and MSCML.







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RFC 5022                         MSCML                    September 2007


   The media server fulfills the role of the Media Resource Function
   (MRF) in the IP Multimedia Subsystem (IMS) [13] as described by 3GPP.
   MSCML and RFC 4240 [2], upon which MSCML builds, are specifically
   focused on the Media resource (Mr) interface which supports
   interactions between application logic and the MRF.

   This document describes a working framework and protocol with which
   there is considerable implementation experience.  Application
   developers and service providers have created several MSCML-based
   services since the availability of the initial version in 2001.  This
   experience is highly relevant to the ongoing work of the IETF,
   particularly the SIP [26], SIPPING [27], MMUSIC [28], and XCON [29]
   work groups, the IMS [30] work in 3GPP, and the CCXML work in the
   Voice Browser Work Group of the W3C.

1.1.  Conventions Used in This Document

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
   document are to be interpreted as described in RFC 2119 [1].

2.  MSCML Approach

   It is critically important to emphasize that the goal of MSCML is to
   provide an application interface that follows the SIP, HTTP, and XML
   development paradigm to foster easier and more rapid application
   deployment.  This goal is reflected in MSCML in two ways.

   First, the programming model is that of peer to peer rather than
   master-slave.  Importantly, this allows the media server to be used
   simultaneously for multiple applications rather than be tied to a
   single point of control.  It also enables standard SIP mechanisms to
   be used for media server location and load balancing.

   Second, MSCML defines constructs and primitives that are meaningful
   at the application level to ensure that programmers are not
   distracted by unnecessary complexity.  For example, the mixing
   resource operates on constructs such as conferences and call
   participants rather than directly on individual media streams.

   The MSCML paradigm is important to the developer community, in that
   developers and operators conceptually write applications about calls,
   conferences, and call legs.  For the majority of developers and
   applications this approach significantly simplifies and speeds
   development.






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RFC 5022                         MSCML                    September 2007


3.  Use of SIP Request Methods

   As mentioned above, MSCML payloads may be carried in either SIP
   INVITE or INFO requests.  The initial INVITE, which creates an
   enhanced conference, MAY include an MSCML payload.  A subsequent
   INVITE to the same Request-URI joins a participant leg to the
   conference.  This INVITE MAY include an MSCML payload.  The initial
   INVITE that establishes an IVR session MUST NOT include an MSCML
   payload.  The client sends all mid-call MSCML payloads for
   conferencing and IVR via SIP INFO requests.

   SIP INVITE requests that contain both MSCML and Session Description
   Protocol (SDP) body parts are used frequently in conferencing
   scenarios.  Therefore, the media server MUST support message bodies
   with the MIME type "multipart/mixed" in SIP INVITE requests.

   The media server transports MSCML responses in the final response to
   the SIP INVITE containing the matching MSCML request or in a SIP INFO
   message.  The only allowable final response to a SIP INFO containing
   a message body is a 200 OK, per RFC 2976 [3].  Therefore, if the
   client sends the MSCML request via SIP INFO, the media server
   responds with the MSCML response in a separate INFO request.  In
   general, these responses are asynchronous in nature and require a
   separate transaction due to timing considerations.

   There has been considerable debate on the use of the SIP INFO method
   for any purpose.  Our experience is that MSCML would not have been
   possible without it.  At the time the first MSCML specification was
   published, the first SIP Event Notification draft had just been
   submitted as an individual submission.  At that time, there was no
   mechanism to link SUBSCRIBE/NOTIFY to an existing dialog.  This
   prevented its use in MSCML, since all events occurred in an INVITE-
   established dialog.  And while SUBSCRIBE/NOTIFY was well suited for
   reporting conference events, its semantics seemed inappropriate for
   modifying a participant leg or conference setting where the only
   "event" was the success or failure of the request.  Lastly, since SIP
   INFO was an established RFC, most SIP stack implementations supported
   it at that time.  We had few, if any, interoperability issues as a
   result.

   More recent developments have provided additional reasons why
   SUBSCRIBE/NOTIFY is not appropriate for use in MSCML.  Use of
   SUBSCRIBE presents two problems.  The first is semantic.  The purpose
   of SUBSCRIBE is to register interest in User Agent state.  However,
   using SUBSCRIBE for MSCML results in the SUBSCRIBE modifying the User
   Agent state.  The second reason SUBSCRIBE is not appropriate is
   because MSCML is inherently call based.  The association of a SIP
   dialog with a call leg means MSCML can be incredibly straightforward.



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RFC 5022                         MSCML                    September 2007


   For example, if one used SUBSCRIBE or other SIP method to send
   commands about some context, one must identify that context somehow.
   Relating commands to the SIP dialog they arrive on defines the
   context for free.  Moreover, it is conceptually easy for the
   developer.  Using NOTIFY to transport MSCML responses is also not
   appropriate, as the NOTIFY would be in response to an implicit
   subscription.  The SIP and SIPPING lists have discussed the dangers
   of implicit subscription.

   In order to guarantee interoperability with this specification, as
   well as with SIP User Agents that are unaware of MSCML, SIP UACs that
   wish to use MSCML services MUST specify a service indicator that
   supports MSCML in the initial INVITE.  RFC 4240 [2] defines the
   service indicator "conf", which MUST be used for MSCML conferencing
   applications.  The service indicator "ivr" MUST be used for MSCML
   interactive voice response applications.  In this specification, only
   "conf" and "ivr" are described.

   The media server MUST support moving the call between services
   through sending the media server a BYE on the existing dialog and
   establishing a new dialog with an INVITE to the desired service.
   Media servers SHOULD support moving between services without
   requiring modification of the previously established SDP parameters.
   This is achieved by sending a re-INVITE on the existing dialog in
   which the Request-URI is modified to specify the new service desired
   by the client.  This eliminates the need for the client to send an
   INVITE to the caller or gateway to establish new SDP parameters.

   The media server, as a SIP UAS, MUST respond appropriately to an
   INVITE that contains an MSCML body.  If MSCML is not supported, the
   media server MUST generate a 415 final response and include a list of
   the supported content types in the response per RFC 3261 [4].  The
   media server MUST also advertise its support of MSCML in responses to
   OPTIONS requests, by including "application/mediaservercontrol+xml"
   as a supported content type in an Accept header.  This alleviates the
   major issues with using INFO for the transport of application data;
   namely, the User Agent's proper interpretation of what is, by design,
   an opaque message request.













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RFC 5022                         MSCML                    September 2007


4.  MSCML Design

4.1.  Transaction Model

   To avoid undue complexity, MSCML establishes two rules regarding its
   usage.  The first is that only one MSCML body may be present in a SIP
   request.  The second is that each MSCML body may contain only one
   request or response.  This greatly simplifies transaction management.
   MSCML syntax does provide for the unique identification of multiple
   requests in a single body part.  However, this is not supported in
   this specification.

   Per the guidelines of RFC 3470 [14], MSCML bodies MUST be well formed
   and valid.

   MSCML is a direct request-response protocol.  There are no
   provisional responses, only final responses.  A request may, however,
   result in multiple notifications.  For example, a request for active
   talker reports will result in a notification for each speaker set.
   This maps to the three major element trees for MSCML: <request>,
   <response>, and <notification>.

   Figure 1 shows a request body.  Depending on the command, one can
   send the request in an INVITE or an INFO.  Figure 2 shows a response
   body.  The SIP INFO method transports response bodies.  Figure 3
   shows a notification body.  The SIP INFO method transports
   notifications.

   <?xml version="1.0" encoding="utf-8"?>
   <MediaServerControl version="1.0">
     <request>
       ... request body ...
     </request>
   </MediaServerControl>

   Figure 1: MSCML Request Format

   <?xml version="1.0" encoding="utf-8"?>
   <MediaServerControl version="1.0">
     <response>
       ... response body ...
     </response>
   </MediaServerControl>

   Figure 2: MSCML Response Format






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   <?xml version="1.0" encoding="utf-8"?>
   <MediaServerControl version="1.0">
     <notification>
       ... notification body ...
     </notification>
   </MediaServerControl>

   Figure 3: MSCML Notification Format

   MSCML requests MAY include a client-defined ID attribute for the
   purposes of matching requests and responses.  The values used for
   these IDs need only be unique within the scope of the dialog in which
   the requests are issued.

4.2.  XML Usage

   In the philosophy of XML as a text-based description language, and
   not as a programming language, MSCML makes the choice of many
   attribute values for readability by a human.  Thus, many attributes
   that would often be "boolean" instead take "yes" or "no" values.  For
   example, what does 'report="false"' or 'report="1"' mean?  However,
   'report="yes"' is clearer: I want a report.  Some programmers prefer
   the precision of a boolean.  To satisfy both styles, MSCML defines an
   XML type, "yesnoType", that takes on the values "yes" and "no" as
   well as "true", "false", "1", and "0".

   Many attributes in the MSCML schema have default values.  In order to
   limit demands on the XML parser, MSCML applies these values at the
   protocol, not XML, level.  The MSCML schema documents these defaults
   as XML annotations to the appropriate attribute.

4.2.1.  MSCML Time Values

   For clarity, time values in MSCML are based on the time designations
   described in the Cascading Style Sheets level 2 (CSS2) Specification
   [15].  Their format consists of a number immediately followed by an
   optional time unit identifier of the following form:

      ms: milliseconds (default)
      s: seconds

   If no time unit identifier is present, the value MUST be interpreted
   as being in milliseconds.  As extensions to [15] MSCML allows the
   string values "immediate" and "infinite", which have special meaning
   for certain timers.






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RFC 5022                         MSCML                    September 2007


5.  Advanced Conferencing

5.1.  Conference Model

   The advanced conferencing model is a star controller model, with both
   signaling and media directed to a central location.  Figure 4 depicts
   a typical signaling relationship between end users' UACs, a
   conference application server, and a media server.

   RFC 4353 [10] describes this model.  The application server is an
   instantiation of the conference focus.  The media server is an
   instantiation of the media mixer.  Note that user-level constructs,
   such as event notifications, are in the purview of the application
   server.  This is why, for example, the media server sends active
   talker reports using MSCML notifications, while the application
   server would instead use the conference package [16] for individual
   notifications to SIP user agents.  Note that we do not recommend the
   use of the conference package for media server to application server
   notifications because none of the filtering and membership
   information is available at the media server.

      +-------+
      | UAC 1 |---\   Public URI  +-------------+
      +-------+    \ _____________| Application |
                    /    /        |   Server    |     Not shown:
      +-------+    /    /         +-------------+     RTP flows directly
      | UAC 2 |---/    /                 | Private    between UACs and
      +-------+       /                  |   URI      media server
          .          /            +--------------+
          :         /             |              |
      +-------+    /              | Media Server |
      | UAC n |---/               |              |
      +-------+                   +--------------+

                          Figure 4: Conference Model

   Each UAC sends an INVITE to a Public Conference URI.  Presumably, the
   client publishes this URI, or it is an ad hoc URI.  In any event, the
   client generates a Private URI, following the rules specified by RFC
   4240 [2].  That is, the URI is of the following form:

   sip:conf=UniqueID@ms.example.net

   where UniqueID is a unique conference identifier and ms.example.net
   is the host name or IP address of the media server.  There is nothing
   to prevent the UACs from contacting the media server directly.
   However, one would expect the owner of the media server to restrict
   who can use its resources.



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   As for basic conferencing, described by RFC 4240 [2], the first
   INVITE to the media server with a UniqueID creates a conference.
   However, in advanced conferencing, the first INVITE MAY include a
   MSCML <configure_conference> payload rather than the SDP of a
   conference participant.  The <configure_conference> payload conveys
   extended session parameters (e.g., number of participants) that SDP
   does not readily express, but the media server must know to allocate
   the appropriate resources.

   When the conference is created by sending an INVITE containing a
   MSCML <configure_conference> payload, the resulting SIP dialog is
   termed the "Conference Control Leg."  This leg has several useful
   properties.  The lifetime of the conference is the same as that of
   its control leg.  This ensures that the conference remains in
   existence even if all participant legs leave or have not yet arrived.
   In addition, when the client terminates the Conference Control Leg,
   the media server automatically terminates all participant legs.  The
   Conference Control Leg is also used for play or record operations
   to/from the entire conference and for active talker notifications.
   Full conference media operations and active talker report
   subscriptions MUST be executed on the Conference Control Leg.

   Creation of a Conference Control Leg is RECOMMENDED because full
   advanced conferencing capabilities are not available without it.
   Clients MUST establish the Conference Control Leg in the initial
   INVITE that creates the conference; it cannot be created later.

   Once the client has created the conference with or without the
   Conference Control Leg, participants can be joined to the conference.
   This is achieved by the client's directing an INVITE to the Private
   Conference URI for each participant.  Using the example conference
   URI given above, this would be sip:conf=UniqueID@ms.example.net.

5.2.  Configure Conference Request <configure_conference>

   The <configure_conference> request has two attributes that control
   the resources the media server sets aside for the conference.  These
   are described in the list below.

   Attributes of <configure_conference>:

   o  reservedtalkers - optional (see note), no default value: The
      maximum number of talker legs allocated for the conference.  Note:
      required when establishing the Conference Control Leg but optional
      in subsequent <configure_conference> requests.






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   o  reserveconfmedia - optional, default value "yes": Controls
      allocation of resources to enable playing or recording to or from
      the entire conference.

   When the reservedtalkers+1st INVITE arrives at the media server, the
   media server SHOULD generate a 486 Busy Here response.  Failure to
   send a 486 response to this condition can cause the media server to
   oversubscribe its resources.

      NOTE: It would be symmetric to have a reservedlisteners parameter.
      However, the practical limitation on the media server is the
      number of talkers for a mixer to monitor.  In either case, the
      client regulates who gets into the conference by either proxying
      the INVITEs from the user agent clients or metering to whom it
      gives the conference URI.

   For example, to create a conference with up to 120 active talkers and
   the ability to play audio into the conference or record portions or
   all of the conference full mix, the client specifies both attributes,
   as shown in Figure 6.

   <?xml version="1.0" encoding="utf-8"?>
   <MediaServerControl version="1.0">
     <request>
       <configure_conference reservedtalkers="120"
         reserveconfmedia="yes"/>
     </request>
   </MediaServerControl>

   Figure 6: 120 Speaker MSCML Example

   In addition to these attributes, a <configure_conference> request MAY
   contain a child <subscribe> element.  The <subscribe> element is used
   to request notifications for conference-wide active talker events.
   Detailed information regarding active talker events is contained in
   Section 5.7.

   The client MUST include a <configure_conference> request in the
   initial INVITE which establishes the conference when creating the
   Conference Control Leg. The client server MUST issue asynchronous
   commands, such as <play>, separately (i.e., in INFO messages) to
   avoid ambiguous responses.

   Media operations on the Conference Control leg are performed
   internally, no external RTP streams are involved.  Accordingly, the
   media server does not expect RTP on the Conference Control Leg.
   Therefore, the client MUST send either no SDP or hold SDP in the
   INVITE request containing a <configure_conference> payload.  The



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   media server MUST treat SDP with all media lines set to "inactive" or
   with connection addresses set to 0.0.0.0 (for backwards
   compatibility) as hold SDP.

   The media server sends a response when it has finished processing the
   <configure_conference> request.  The format of the
   <configure_conference> response is detailed in Section 10.2.

5.3.  Configure Leg Request <configure_leg>

   Conference legs have a number of properties the client can modify.
   These are set using the <configure_leg> request.  This request has
   the attributes described in the list below.

   Attributes of <configure_leg>:

   o  type - optional, default value "talker": Consider this leg's audio
      for inclusion in the output mix.  Alternative is "listener".

   o  dtmfclamp - optional, default value "yes": Remove detected DTMF
      digits from the input audio.

   o  toneclamp - optional, default value "yes": Remove tones from the
      input audio.  Tones include call progress tones and the like.

   o  mixmode - optional, default value "full": Be a candidate for the
      full mix.  Alternatives are "mute", to disallow media in the mix,
      "parked", to disconnect the leg's media streams from the
      conference for IVR operations, "preferred", to give this stream
      preferential selection in the mix (i.e., even if not loudest
      talker, include media, if present, from this leg in the mix), and
      "private", which enables personalized mixes.

   In addition to these attributes, there are four child elements
   defined for <configure_leg>.  These are <inputgain>, <outputgain>,
   <configure_team>, and <subscribe>.

   The first two, <inputgain> and <outputgain>, modify the gain applied
   to the input and output audio streams, respectively.  These may
   contain <auto>, to use automatic gain control (AGC) or <fixed>.  The
   <auto> element has the attributes "startlevel", "targetlevel", and
   "silencethreshold".  All the parameters are in dB.  The <fixed>
   element has the attribute "level", which is in dB.  The default for
   both <inputgain> and <outputgain> is <fixed>.  The media server MAY







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   silently cap <inputgain> or <outputgain> requests that exceed the
   gain limits imposed by the platform.

   Clients most commonly manipulate only the input gain for a conference
   leg and rely on the mixer to set an optimum output gain based on the
   inputs currently in the mix.  However, as described above, MSCML does
   allow for manipulation of the output gain as well.  Some of the IVR
   commands, such as <play>, enable control of the output gain for
   content playback operations.  The interaction of conference output
   gain and IVR playback gain controls is described in Section 6.1.1.
   Note that <inputgain> and <outputgain> settings apply only to
   conference legs and do not apply to IVR sessions.

   The <configure_team> element is used to create and manipulate groups
   for personalized mixes.  Details of personalized mixes are discussed
   in Section 5.8.

   The <subscribe> element is used to request notifications for call leg
   related events, such as asynchronous DTMF digit reports.  Detailed
   information regarding call leg events is discussed in Section 7.

   If the default parameters are acceptable for the leg the client
   wishes to enter into the conference, then a normal SIP INVITE, with
   no MSCML body, is sufficient.  However, if the client wishes to
   modify one or more of the parameters, the client can include a MSCML
   body in addition to the SDP body.

   The client can modify the conference leg parameters during the
   conference by issuing a SIP INFO on the dialog representing the
   conference leg.  Of course, the client cannot modify SDP in an INFO
   message.

   The media server sends a response when it has finished processing the
   <configure_leg> request.  The format of the <configure_leg> response
   is detailed in Section 10.3.

5.4.  Terminating a Conference

   To remove a leg from the conference, the client issues a SIP BYE
   request on the selected dialog representing the conference leg.

   The client can terminate all legs in a conference by issuing a SIP
   BYE request on the Conference Control Leg.  If one or more
   participants are still in the conference when the media server
   receives a SIP BYE request on the Conference Control Leg, the media
   server issues SIP BYE requests on all remaining conference legs to
   ensure cleanup of the legs.




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   The media server returns a 200 OK to the SIP BYE request as it sends
   BYE requests to the other legs.  This is because we cannot issue a
   provisional response to a non-INVITE request, yet the teardown of the
   other legs may exceed the retransmission timer limits of the original
   request.  While the conference is being cleaned up, the media server
   MUST reject any new INVITEs to the terminated conference with a 486
   Busy Here response.  This response indicates that the specified
   conference cannot accept any new members, pending deletion.

5.5.  Conference Manipulation

   Once the conference has begun, the client can manipulate the
   conference as a whole or a particular participant leg by issuing
   commands on the associated SIP dialog.  For example, by sending MSCML
   requests on the Conference Control Leg the client can request that
   the media server record the conference, play a prompt to the
   conference, or request reports on active talker events.  Similarly,
   the client may mute a participant leg, configure a personalized mix
   or request reports for call leg events, such as DTMF keypresses.

   Figure 7 shows an example of an MSCML command that plays a prompt to
   all conference participants.

   <?xml version="1.0" encoding="utf-8"?>
   <MediaServerControl version="1.0">
     <request>
       <play>
         <prompt>
           <audio url="http://prompts.example.net/en_US/welcome.au"/>
         </prompt>
       </play>
     </request>
   </MediaServerControl>

   Figure 7: Full Conference Audio Command - Play

   A client can modify a leg by issuing an INFO on the dialog associated
   with the participant leg.  For example, Figure 8 mutes a conference
   leg.

   <?xml version="1.0" encoding="utf-8"?>
   <MediaServerControl version="1.0">
     <request>
       <configure_leg mixmode="mute"/>
     </request>
   </MediaServerControl>

   Figure 8: Sample Change Leg Command



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   In Figure 7, we saw a request to play a prompt to the entire
   conference.  The client can also request to play a prompt to an
   individual call leg.  In that case, the MSCML request is issued
   within the SIP dialog of the desired conference participant.

   Section 6 describes the interactive voice response (IVR) services
   offered by MSCML.  If an IVR command arrives on the control channel,
   it takes effect on the whole conference.  This is a mechanism for
   playing prompts to the entire conference (e.g., announcing new
   participants).  If an IVR command arrives on an individual leg, it
   only affects that leg.  This is a mechanism for interacting with
   users, such as the creation of "waiting rooms", allowing a user to
   mute themselves using key presses, allowing a moderator to out-dial,
   etc.

   A participant leg MUST be configured with mixmode="parked" prior to
   the issuance of any IVR commands with prompt content ('prompturl'
   attribute or <prompt> element).  Parking the leg isolates the
   participant's input and output media from the conference and allows
   use of those streams for playing and recording purposes.  However,
   the mixmode has no effect if just digit collection or recording is
   desired. <playcollect> and <playrecord> requests without prompt
   content MAY be sent on participant legs without setting
   mixmode="parked".

5.6.  Video Conferencing

   MSCML-controlled advanced conferences, as well as RFC 4240 [2]
   controlled basic conferences, implicitly support video conferencing
   in the form of video switching.  In video switching, the video stream
   of the loudest talker (with some hysteresis) is sent to all
   participants other than that talker.  The loudest talker receives the
   video stream from the immediately prior loudest talker.

   Media servers MUST ensure that participants receive video media
   compatible with their session.  For example, a participant who has
   established an H.263 video stream will not receive video from another
   participant employing H.264 media.  Media servers SHOULD implement
   video transcoding to minimize media incompatibilities between
   participants.

   The media server MUST switch video streams only when it receives a
   refresh video frame.  A refresh frame contains all the video
   information required to decode that frame (i.e., there is no
   dependency on data from previous video frames).






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   Refresh frames are large and generally sent infrequently to conserve
   network bandwidth.  The media server MUST implement standard
   mechanisms to request that the new loudest talker's video encoder
   transmits a refresh frame to ensure that video can be switched
   quickly.

5.7.  Conference Events

   A client can subscribe for periodic active talker event reports that
   indicate which participants are included in the conference mix.  As
   these are conference-level events, the subscription and notifications
   are sent on the Conference Control Leg.

   Media servers MAY impose limits on the minimum interval for active
   talker reports for performance reasons.  If the client request is
   below the imposed minimum, the media server SHOULD set the interval
   to the minimum value supported.  To limit unnecessary notification
   traffic, the media server SHOULD NOT send a report if the active
   talker information for the conference has not changed during the
   reporting interval.

   A request for an active talker report is in Figure 9.  The active
   talker report enumerates the current call legs in the mix.

   <?xml version="1.0" encoding="utf-8"?>
   <MediaServerControl version="1.0">
     <request>
       <configure_conference>
         <subscribe>
           <events>
             <activetalkers report="yes" interval="60s"/>
           </events>
         </subscribe>
       </configure_conference>
     </request>
   </MediaServerControl>

   Figure 9: Active Talker Request

   Event notifications are sent in SIP INFO messages.  Figure 10 shows
   an example of a report.










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   <?xml version="1.0" encoding="utf-8"?>
   <MediaServerControl version="1.0">
     <notification>
       <conference uniqueid="ab34h76z" numtalkers="47">
         <activetalkers>
           <talker callid="myhost4sn123"/>
           <talker callid="myhost2sn456"/>
           <talker callid="myhost12sn78"/>
         </activetalkers>
       </conference>
     </notification>
   </MediaServerControl>

   Figure 10: Active Talker Event Example

   The value of the "callid" attribute in the <talker> element
   corresponds to the value of the SIP Call-ID header of the associated
   dialog.  This enables the client to associate the active talker with
   a specific participant leg.

5.8.  Conferencing with Personalized Mixes

   MSCML enables clients to create personalized mixes through the
   <configure_team> element for scenarios where the standard mixmode
   settings do not provide sufficient control.  The <configure_team>
   element is a child of <configure_leg>.

   To create personalized mixes, the client has to identify the
   relationships among the participants.  This is accomplished by
   manipulating two MSCML objects.  These objects are:

   1.  The list of team members (<teammate> elements), set using
       <configure_team>

   2.  The mixmode attribute set through <configure_leg>

   The media server uses the values of these objects to determine which
   audio inputs to combine for output to the participant.  In a normal
   conference, each participant hears the conference mix minus their own
   input if they are part of the mixed output.  The team list enables
   the client to specify other participants that the leg can hear in
   addition to the normal mixed output.  Note that personalized mix
   settings apply only to audio media and do not affect video switching.

   Team relationships are implicitly symmetric.  If the client sets
   participant A as a team member of participant B, then the media
   server automatically sets participant B as a team member for A.




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   The id attribute set through <configure_leg> is used to identify the
   various participants.  A unique ID MUST be assigned to each
   participant included in a personalized mix.  The IDs used MUST be
   unique within the scope of the conference in which they appear.

   By itself, the team list only defines those participants that the leg
   can hear.  The mixmode attribute of each team member determines
   whether to include their audio input in the personalized mix.  If the
   client sets the teammate's mixmode to private, then it is part of the
   mix.  If the mixmode is set to any other value, it is not.

5.8.1.  MSCML Elements and Attributes for Personalized Mixes

   Control of personalized mixes rely on two major MSCML elements:

   1.  <configure_leg>, using the mixmode attribute setting
       mixmode="private"

   2.  <configure_team>

   The <configure_team> element allows the user to make the participants
   members of a team within a specific conference.  It is a child of the
   <configure_leg> parent element.

   The client sends the <configure_team> element in a <configure_leg>
   request in either a SIP INVITE or SIP INFO.

   o  In an INVITE, to join a participant whose properties differ from
      the properties established for the conference as a whole.

   o  In an INFO, to change the properties for an existing leg.

   The two attributes of the configure_team element are "id" and
   "action".  The id attribute MUST contain the unique ID of the leg
   being modified, as set in the original <configure_leg> request.  The
   action attribute can take on the values "add", "delete", "query", and
   "set".  The default value is "query".  This attribute allows the user
   to modify the team list.  Table 1 describes the actions that can be
   performed on the team list.












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   +--------+----------------------------------------------------------+
   | Action | Description                                              |
   +--------+----------------------------------------------------------+
   | add    | Adds a teammate to the mix.                              |
   | delete | Deletes a teammate from the mix.                         |
   | query  | Returns the teammate list to the requestor.  This is the |
   |        | default value.                                           |
   | set    | Creates a team list when followed by <teammate id="n">   |
   |        | and also removes all the teammates from the team list    |
   |        | for example, when the creator (originator) of the team   |
   |        | list on that specific conference leg wants to remove all |
   |        | of the teammates from the team.  If the set operation    |
   |        | removes all teammates from a participant, that           |
   |        | participant hears the full conference mix.               |
   +--------+----------------------------------------------------------+

                      Table 1: Configure Team Actions

5.8.2.  Example Usage of Personalized Mixes

   A common use of personalized mixing is to support coaching of one
   participant by another.  The coaching scenario includes three
   participants:
   1.  The Supervisor, who coaches the agent.
   2.  The Agent, who interacts with the customer.
   3.  The Customer, who interacts with the agent.

   Table 2 illustrates the details of the coached conference topology.

   +-------------+------------+------------+---------+-----------------+
   | Participant | ID         | Team       | Mixmode | Hears           |
   |             |            | Members    |         |                 |
   +-------------+------------+------------+---------+-----------------+
   | Supervisor  | supervisor | Agent      | Private | customer +      |
   |             |            |            |         | agent           |
   | Agent       | agent      | Supervisor | Full    | customer +      |
   |             |            |            |         | supervisor      |
   | Customer    | customer   | none       | Full    | agent           |
   +-------------+------------+------------+---------+-----------------+

                    Table 2: Coached Conference Example

   To create this topology, the client performs the following actions:

   1.  The client joins each leg to the conference, being certain to
       include a unique ID in the <configure_leg> request.  The leg ID
       needs to be unique only within the scope of the conference to
       which it belongs.



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   2.  The client configures the teammate list and mixmode of each
       participant, as required.

   Both actions (steps 1 and 2) may be combined in a single MSCML
   request.  The following sections detail these actions and their
   corresponding MSCML payloads.

5.8.2.1.  Create the Conference

   Before joining any participants, the client must create the
   conference by sending a SIP INVITE that contains an MSCML
   <configure_conference> request with a unique conference identifier.

5.8.2.2.  Joining and Configuring the Coach

   Join the coach leg to the conference and configure its desired
   properties by sending a SIP INVITE containing a <configure_leg>
   request.  The <configure_leg> element sets the leg's unique ID to
   supervisor and its mixmode to private.

   The corresponding MSCML request is as follows.

   <?xml version="1.0"?>
   <MediaServerControl version="1.0">
     <request>
       <configure_leg id="supervisor" mixmode="private"/>
     </request>
   </MediaServerControl>

   Figure 11: Join Coach Request

   Note that the client cannot configure the teammate list for the coach
   yet, as there are no other participants in the conference.  One must
   join a participant to the conference before one can add it as a
   teammate for another leg.

5.8.2.3.  Joining and Configuring the Agent

   Join the agent leg to the conference and configure its desired
   properties by sending a SIP INVITE containing a <configure_leg>
   request.  The <configure_leg> element sets the leg's unique ID to
   "agent" and sets the supervisor as a team member of the agent.
   Because team member relationships are symmetric, this action also
   adds the agent as a team member for the coach.







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   The corresponding MSCML request is as follows.
   <?xml version="1.0"?>
   <MediaServerControl version="1.0">
    <request>
       <configure_leg id="agent">
         <configure_team action="set">
           <teammate id="supervisor"/>
         </configure_team>
       </configure_leg>
     </request>
   </MediaServerControl>

   Figure 12: Join Agent Request

   Because the desired mixmode for this leg is full, which is the
   default value, there is no need to set it explicitly.

5.8.2.4.  Joining and Configuring the Client

   Join the client leg to the conference and configure its desired
   properties by sending a SIP INVITE containing a <configure_leg>
   request.  The <configure_leg> element simply sets the leg's unique ID
   to "customer".  The media server does not need further configuration
   because the desired mixmode, full, is the default and the customer
   has no team members.

   The corresponding MSCML request is as follows.
   <?xml version="1.0"?>
   <MediaServerControl version="1.0">
     <request>
       <configure_leg id="customer"/>
     </request>
   </MediaServerControl>

   Figure 13: Join Client Request

   Strictly speaking, it is not a requirement that the client give the
   customer leg a unique ID because it will not be a team member.
   However, when using coached conferencing, we RECOMMEND that one
   assign a unique ID to each leg in the initial INVITE request.
   Assigning a unique ID eliminates the need to set it later by sending
   a SIP INFO if one later desires personalized mixing for the customer
   leg.

   The conference is now in the desired configuration, shown previously
   in Table 2.





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6.  Interactive Voice Response (IVR)

   In the IVR model, the media server acts as a media-processing proxy
   for the UAC.  This is particularly useful when the UAC is a media
   gateway or other device with limited media processing capability.

   The typical use case for MSCML is when there is an application server
   that is the MSCML client.  The client can use the SIP Service URI
   concept (RFC 3087) to initiate a service.  The client then uses RFC
   4240 [2] to initiate a MSCML session on a media server.  These
   relationships are shown in Figure 14.

                             SIP       +--------------+
                         Service URI   | Application  |
                      /----------------|    Server    |
                     /(e.g., RFC 3087) +--------------+
                    /                        |  MSCML
                   /                     SIP | Session
                  /                    +--------------+
          +-----+/       RTP           |              |
          | UAC |======================| Media Server |
          +-----+                      |              |
                                       +--------------+

                               Figure 14: IVR Model

   The IVR service supports basic Interactive Voice Response functions,
   playing announcements, collecting DTMF digits, and recording, based
   on Media Server Control Markup Language (MSCML) directives added to
   the message body of a SIP request.  The major MSCML IVR requests are
   <play>, <playcollect>, and <playrecord>.

   Multifunction media servers MUST use the URI conventions described in
   RFC 4240 [2].  The service indicator for MSCML IVR MUST be set to
   "ivr", as shown in the following example:

   sip:ivr@ms.example.net

   The VoiceXML IVR service indicator is "dialog".  This service
   indicator MUST NOT be used for any other interactive voice response
   control mechanism.

   The media server MUST accept MSCML IVR payloads in INFO requests and
   MUST NOT accept MSCML IVR payloads in the initial or subsequent
   INVITEs.  The INFO method reduces certain timing issues that occur
   with INVITEs and requires less processing on both the client and
   media server.




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   The media server notifies the client that the command has completed
   through a <response> message containing final status information and
   associated data such as collected DTMF digits.

   The media server does not queue IVR requests.  If the media server
   receives a new IVR request while another is in progress, the media
   server stops the first operation and it carries out the new request.
   The media server generates a <response> message for the first request
   and returns any data collected up to that point.  If a client wishes
   to stop a request in progress but does not wish to initiate another
   operation, it issues a <stop> request.  This also causes the media
   server to generate a <response> message.

   The media server treats a SIP re-INVITE that modifies the established
   SDP parameters as an implicit <stop> request.  Examples of such SDP
   modifications include receiving hold SDP or removing an audio or
   video stream.  When this occurs, the media server immediately
   terminates the running <play>, <playcollect>, or <playrecord> request
   and sends a <response> indicating "reason=stopped".

6.1.  Specifying Prompt Content

   The MSCML IVR requests support two methods of specifying content to
   be delivered to the user.  These are the <prompt> element and the
   prompturl attribute.  Clients MUST NOT utilize both methods in a
   single IVR request.  Clients SHOULD use the more flexible <prompt>
   mechanism.  Use of the prompturl attribute is deprecated and may not
   be supported in future MSCML versions.

6.1.1.  Use of the Prompt Element

   The <prompt> element MAY be included in the body of a <play>,
   <playcollect>, or <playrecord> request to specify a prompt sequence
   to be delivered to the caller.  The prompt sequence consists of one
   or more references to physical content files, spoken variables, or
   dynamic URLs that return a sub-sequence of files or variables.  In
   addition, the <prompt> element has several attributes that control
   playback of the included content.  These are described in the list
   below.

   Attributes of <prompt>:

   o  baseurl - optional, no default value: For notational convenience,
      as well as reducing the MSCML payload size, the "baseurl"
      attribute is used to specify a base URL that is prepended to any
      other URLs in the sequence that are not fully qualified.





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   o  delay - optional, default value "0": The "delay" attribute to the
      prompt element specifies the time to pause between repetitions of
      the <prompt> sequence.  It has no effect on the first iteration of
      the sequence.  Expressed as a time value (Section 4.2.1) from 0
      onwards.

   o  duration - optional, default value "infinite": The "duration"
      attribute to the prompt element controls the maximum amount of
      time that may elapse while the media server repeats the sequence.
      This allows the client to set an upper bound on the length of
      play.  Expressed as a time value (Section 4.2.1) from 1ms onwards
      or the strings "immediate" and "infinite".  "Immediate" directs
      the media server to end play immediately, whereas "infinite"
      indicates that the media server imposes no limit.

   o  gain - optional, default value "0": Sets the absolute gain to be
      applied to the content contained in <prompt>.  The value of this
      attribute is specified in units of dB.  The media server MAY
      silently cap values that exceed the gain limits imposed by the
      platform.  The level reverts back to its original value when
      playback of the content contained in <prompt> has been completed.

   o  gaindelta - optional, default value "0": Sets the relative gain to
      be applied to the content contained in <prompt>.  The value of
      this attribute is specified in units of dB.  The media server MAY
      silently cap values which exceed the gain limits imposed by the
      platform.  The level reverts back to its original value when
      playback of the content contained in <prompt> has been completed.

   o  rate - optional, default value "0": Specifies the absolute
      playback rate of the content relative to normal as either a
      positive percentage (faster) or a negative percentage (slower).
      Any value that attempts to set the rate above the maximum allowed
      or below the minimum allowed silently sets the rate to the maximum
      or minimum.  The rate reverts back to its original value when
      playback of the content contained in <prompt> has been completed.

   o  ratedelta - optional, default value "0": Specifies the playback
      rate of the content relative to it's current rate as either a
      positive percentage (faster) or negative percentage (slower).  Any
      value that attempts to set the rate above the maximum allowed or
      below the minimum allowed silently sets the rate to the maximum or
      minimum.  The rate reverts back to its original value when
      playback of the content contained in <prompt> has completed.







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   o  locale - optional, no default value: Specifies the language and
      country variant used for resolving spoken variables.  The language
      is defined as a two-letter code per ISO 639.  The country variant
      is also defined as a two-letter code per ISO 3166.  These codes
      are concatenated with a single underscore (%x5F) character.

   o  offset - optional, default value "0": A time value (Section 4.2.1)
      which specifies the time from the beginning of the sequence at
      which play is to begin.  Offset only applies to the first
      repetition; subsequent repetitions begin play at offset 0.
      Allowable values are positive time values from 0 onwards.  When
      the sequence consists of multiple content files, the offset may
      select any point in the sequence.  If the offset value is greater
      than the total time of the sequence, it will "wrap" to the
      beginning and continue from there until the media server reaches
      the specified offset.

   o  repeat - optional, default value "1": The "repeat" attribute to
      the prompt element controls the number of times the media server
      plays the sequence in the <prompt> element.  Allowable values are
      integers from 0 on and the string "infinite", which indicates that
      repetition should occur indefinitely.  For example, "repeat=2"
      means that the sequence will be played twice, and "repeat=0",
      which is allowed, means that the sequence is not played.

   o  stoponerror - optional, default value "no": Controls media server
      handling and reporting of errors encountered when retrieving
      remote content.  If set to "yes", content play will end if a fetch
      error occurs, and the response will contain details regarding the
      failure.  If set to "no", the media server will silently move on
      to the next URL in the sequence if a fetch failure occurs.

   Clients MUST NOT include both 'gain' and 'gaindelta' attributes
   within a single <prompt> element.

   When the client explicitly controls the output gain on a conference
   leg, as described in Section 5.3, the 'gain' and 'gaindelta'
   attributes SHOULD interact with the conference leg output gain
   settings in the following manner.

   o  Conference leg output gain set to <fixed>: The operation of the
      'gain' and 'gaindelta' attributes are unchanged.  However, the
      baseline gain value before any playback changes are applied is the
      value specified for the conference leg.

   o  Conference leg output gain set to <auto>: When playback gain
      controls are used, the automatic gain control settings for the leg
      are suspended for the duration of the playback operation.  The



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      operation of the 'gain' and 'gaindelta' attributes are unchanged.
      The automatic gain control settings are reinstated when playback
      has finished.

   Media servers SHOULD support rate controls for content.  However,
   media servers MAY silently ignore rate change requests if content
   limitations do not allow the request to be honored.  Clients MUST NOT
   include both 'rate' and 'ratedelta' attributes within a single
   <prompt> element.

   Figure 16 shows a sample prompt block.

   <prompt stoponerror="yes"
     baseurl="file:////var/mediaserver/prompts/"
     locale="en_US" offset="0" gain="0" rate="0"
     delay="0" duration="infinite" repeat="1">
     <audio url="num_dialed.raw" encoding="ulaw"/>
     <variable type="dig" subtype="ndn" value="3014170700"/>
     <audio url="num_invalid.wav"/>
     <audio url="please_check.wav"/>
   </prompt>

   Figure 16: Prompt Block Example

6.1.1.1.  <audio> and <variable> Elements

   Clients compose prompt sequences using the <audio> and <variable>
   elements.  An <audio> element MAY refer to content that contains
   audio, video, or both; the generic name is preserved for backwards
   compatibility.  The <audio> element has the attributes described in
   the list below.

   Attributes of <audio>:

   o  url - required, no default value: The URL of the content to be
      retrieved and played.  The target may be a local or remote (NFS)
      "file://" scheme URL or an "http://" or "https://" scheme URL.  If
      the URL is not fully qualified and a "baseurl" attribute was set,
      the value of the "baseurl" attribute will be prepended to this
      value to generate the target URL.

   o  encoding - optional, default value "ulaw": Specifies the content
      encoding for file formats that are not self-describing (e.g.,
      .WAV).  Allowable values are "ulaw", "alaw", and "msgsm".  This
      attribute only affects "file://" scheme URLs.

   o  gain - optional, default value "0": Sets the absolute gain to be
      applied to the content URL.  The value of this attribute is



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      specified in units of dB.  The media server MAY silently cap
      values that exceed the gain limits imposed by the platform.  The
      level reverts back to its original value when playback of the
      content URL has been completed.

   o  gaindelta - optional, default value "0": Sets the relative gain to
      be applied to the content URL.  The value of this attribute is
      specified in units of dB.  The media server MAY silently cap
      values that exceed the gain limits imposed by the platform.  The
      level reverts back to its original value when playback of the
      content URL has been completed.

   o  rate - optional, default value "0": Specifies the absolute
      playback rate of the content relative to normal as either a
      positive percentage (faster) or a negative percentage (slower).
      Any value that attempts to set the rate above the maximum allowed
      or below the minimum allowed silently sets the rate to the maximum
      or minimum.  The rate reverts back to its original value when
      playback of the content URL has been completed.

   o  ratedelta - optional, default value "0": Specifies the playback
      rate of the content relative to it's current rate as either a
      positive percentage (faster) or a negative percentage (slower).
      Any value that attempts to set the rate above the maximum allowed
      or below the minimum allowed silently sets the rate to the maximum
      or minimum.  The rate reverts back to its original value when
      playback of the content URL has been completed.

   Clients MUST NOT include both 'gain' and 'gaindelta' attributes
   within a single <audio> element.

   When the client explicitly controls the output gain on a conference
   leg, as described in Section 5.3, the 'gain' and 'gaindelta'
   attributes SHOULD interact with the conference leg output gain
   settings in the following manner.

   o  Conference leg output gain set to <fixed>: The operation of the
      'gain' and 'gaindelta' attributes are unchanged.  However, the
      baseline gain value before any playback changes are applied is the
      value specified for the conference leg.

   o  Conference leg output gain set to <auto>: When playback gain
      controls are used, the automatic gain control settings for the leg
      are suspended for the duration of the playback operation.  The
      operation of the 'gain' and 'gaindelta' attributes are unchanged.
      The automatic gain control settings are reinstated when playback
      has finished.




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   Media servers SHOULD support rate controls for content.  However,
   media servers MAY silently ignore rate change requests if content
   limitations do not allow the request to be honored.  Clients MUST NOT
   include both 'rate' and 'ratedelta' attributes within a single
   <audio> element.

   Media servers MUST support local and remote (NFS) "file://" scheme
   URLs and "http://" and "https://" scheme URLs for content retrieval.

      NOTE: The provisioning of NFS mount points and their mapping to
      the "file://" schema is purely a local matter at the media server.

   MSCML also supports "http://" and "https://" scheme URLS that return
   a list of physical URLs using the "text/uri-list" MIME type.  This
   facility provides flexibility for applications to dynamically
   generate prompt sequences at execution time and enables separation of
   this function from the client and media server.

   Spoken variables are specified using the <variable> element.  This
   element has the attributes described in the list below.  MSCML's
   spoken variables are based on those described in Audio Server
   Protocol [17].

   Attributes of <variable>:

   o  type - required, no default value: Specifies the major type format
      of the spoken variable to be played.  Allowable values are "dat"
      (date), "dig" (digit), "dur" (duration), "mth" (month), "mny"
      (money), "num" (number), "sil" (silence), "str" (string), "tme"
      (time), and "wkd" (weekday).

   o  subtype - optional, no default value: Specifies the minor type
      format of the spoken variable to be played.  Allowable values
      depend on the value of the corresponding "type" attribute.
      Possible values are "mdy", "ymd", and "dmy" for dates, "t12" and
      "t24" for times, "gen", "ndn", "crd", and "ord" for digits, and
      "USD" for money.

   o  value - required, no default value: A string that will be
      interpreted based on the formatting information specified in the
      "type" and "subtype" attributes and the "locale" attribute of the
      parent <prompt> element to render the spoken variable.

   If the "locale" attribute was not specified in <prompt>, the media
   server SHOULD make a selection based on platform configuration.  If
   the precise "locale" requested cannot be honored, the media server
   SHOULD select the closest match based on the available content.




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   IVR applications normally require specialized prompt content that is
   authored by the application provider.  To deliver a quality user
   interaction, the specialized prompts and spoken variables must be
   generated by the same speaker.  Since the media server inherently
   supports multiple simultaneous applications, it is extremely
   difficult to provision all the necessary application prompts and
   matching spoken variable content locally on the media server.
   Therefore, we STRONGLY RECOMMEND that clients employ the dynamic URL
   mechanism described earlier to generate spoken variables using an
   external web server that returns "text/uri-list" content.

6.2.  Multimedia Processing for IVR

   MSCML IVR requests implicitly support multimedia content.  Multimedia
   capabilities are controlled by the audio and video media negotiated
   for the dialog and the content specified by the client for play and
   record operations.  If the content specified for delivery contains
   both audio and video tracks and the dialog has audio and video
   streams, both tracks are streamed to the caller.  Likewise, if the
   dialog has both audio and video streams and the content format
   specified supports both (e.g., .3gp files) the media server records
   both streams to the file.

   If there is a mismatch between the real time media and specified
   content, the media server MUST play or record the appropriate content
   tracks rather than failing the request.  For example, if the client
   has requested playback of content with audio and video tracks but
   only audio media has been established for the dialog, the media
   server should play the audio track.  If the dialog has both audio and
   video media but the content is audio-only, the media server MAY
   stream a pre-provisioned video track to the caller.  Media servers
   SHOULD implement video transcoding functions to minimize
   incompatibilities between real time media and content.

   The media server MUST begin recording video media only when it
   receives a refresh video frame.  A refresh frame contains all the
   video information required to decode that frame (i.e., there is no
   dependency on data from previous video frames).  Refresh frames are
   large and generally sent infrequently to conserve network bandwidth.
   The media server MUST implement standard mechanisms to request that
   the caller (video encoder) transmit a refresh frame to ensure video
   recording begins quickly.  The media server MUST begin recording the
   audio track immediately while waiting to receive the video refresh
   frame.







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6.3.  Playing Announcements <play>

   The client issues a <play> request to play an announcement without
   interruption and with no digit collection.  One use, for example, is
   to announce the name of a new participant to the entire conference.
   The <play> request has the attributes described in the list below.

   Attributes of <play>:

   o  id - optional, no default value: Specifies a client-defined ID for
      purposes of matching requests and responses.

   o  offset - optional, default value "0": Specifies the time from the
      beginning of the URL specified in the 'prompturl' attribute at
      which play will begin.  Expressed as a time value (Section 4.2.1)
      from 0 onwards.  If the offset value is greater than the total
      time of the content, it will "wrap" to the beginning and continue
      from there until the media server reaches the specified offset.
      NOTE: Use of this attribute is deprecated.

   o  promptencoding - optional, no default value: Specifies the content
      encoding for file formats that are not self-describing (e.g.,
      .WAV).  Allowable values are "ulaw", "alaw", and "msgsm".  This
      attribute only affects "file://" scheme URLs.  NOTE: Use of this
      attribute is deprecated.

   o  prompturl - optional, no default value: The URL of the content to
      be retrieved and played.  The target may be a local or remote
      (NFS) "file://" scheme URL or an "http://" or "https://" scheme
      URL.  NOTE: Use of this attribute is deprecated.

   The <play> request has one child element defined, <prompt>.  Use of
   <prompt> is described in Section 6.1.1.

   The client MUST NOT use both the <prompt> element and "prompturl"
   attribute in a single request.  As previously discussed, the
   "prompturl" attribute is supported for backwards compatibility with
   older MSCML applications, but its use is deprecated.  The more
   flexible <prompt> element SHOULD be used instead.

   The following play request (Figure 17) example shows the delivery of
   a complex prompt sequence consisting of content accessed via NFS and
   spoken variables.








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   <?xml version="1.0"?>
   <MediaServerControl version="1.0">
     <request>
       <play id="332985001">
         <prompt stoponerror="yes"
           baseurl="file:////var/mediaserver/prompts/"
           locale="en_US" offset="0" gain="0" rate="0"
           delay="0" duration="infinite" repeat="1">
           <audio url="num_dialed.raw" encoding="ulaw"/>
           <variable type="dig" subtype="ndn" value="3014170700"/>
           <audio url="num_invalid.wav"/>
           <audio url="please_check.wav"/>
         </prompt>
       </play>
     </request>
   </MediaServerControl>

   Figure 17: <Play> Request Example

   When the announcement has finished playing, the media server sends a
   <response> payload to the client in a SIP INFO message.  Details
   regarding the format of <play> responses are provided in Section
   10.4.

6.4.  Prompt and Collect <playcollect>

   The client issues a <playcollect> request to play an announcement
   (optional) and collect digits.  The <playcollect> request is executed
   in two phases, prompt and collect.  If the client specifies prompt
   content to be played, using the <prompt> element or prompturl
   attribute, the media server plays the content before starting the
   collection phase.  If no prompt content is specified, the collect
   phase begins immediately.

   The basic attributes of <playcollect> are the same as those of
   <play>, which were described in Section 6.3.  In addition to these
   basic attributes, <playcollect> defines others which control digit
   buffering and barge-in behavior, collection timers, special purpose
   DTMF key functions, and logging of user DTMF input.  Each functional
   category and its attributes are described below.











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6.4.1.  Control of Digit Buffering and Barge-In

   Whenever the media server is processing a call that specifies an
   MSCML service (i.e., "conf" and "ivr"), the media server continuously
   looks for DTMF digits and places them in a quarantine buffer.  The
   quarantine buffer is examined when a <playcollect> request is
   received.  The media server compares any previously buffered digits
   for barge-in, and to look for matches with DTMF grammars or special
   purpose keys.  This provides the type-ahead behavior for menu
   traversal and other types of IVR interactions.

   Attributes for Control of Digit Buffering and Barge-In:

   o  cleardigits - optional, default value "no": Specifies whether
      previous user input should be considered or ignored for barge-in
      purposes and DTMF matching.  When it is set to "yes", any
      previously buffered digits are removed, so prior user input is
      ignored.  If it is set to "no", previously buffered digits will be
      considered.  If "cleardigits" is set to "no" and barge-in is
      enabled, previously buffered digits will immediately terminate the
      prompt phase.  In this case, the prompt is not played, and digit
      collection begins immediately.

   o  barge - optional, default value "yes": Specifies whether user
      input will barge the prompt and force transition to the collect
      phase.  When it is set to "yes", a DTMF input will barge the
      prompt.  When it is set to "no", the prompt phase cannot be
      barged, and any user input during the prompt is placed in the
      quarantine buffer for inspection during the collect phase.  Note
      that if the "barge" attribute is set to "no", the "cleardigits"
      attribute implicitly has a value of "yes".  This ensures that the
      media server does not leave DTMF input that occurred prior to the
      current collection in the quarantine buffer after the request is
      completed.

6.4.2.  Mapping DTMF Keys to Special Functions

   The client can define mappings between DTMF digits and special
   functions.  The media server invokes the special function if the
   associated DTMF digit is detected.  MSCML has two attributes that
   define mappings that affect termination of the collect phase.  These
   attributes are described in the list below.









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   DTMF Key Mappings for <playcollect>:

   o  escapekey - optional, default value "*": Specifies a DTMF key that
      indicates that the user wishes to terminate the current operation
      without saving any input collected to that point.  Detection of
      the mapped DTMF key terminates the request immediately and
      generates a response.

   o  returnkey - optional, default value "#": Specifies a DTMF key that
      indicates that the user has completed input and wants to return
      all collected digits to the client.  When the media server detects
      the returnkey, it immediately terminates collection and returns
      the collected digits to the client in the <response> message.

   MSCML defines three additional mappings to enable video cassette
   recorder (VCR) type controls while playing a prompt sequence.  Media
   servers SHOULD support VCR controls.  However, if the media server
   does not support VCR controls, it MUST silently ignore DTMF inputs
   mapped to VCR functions and complete the <playcollect> request.  The
   VCR control attributes are described in the list below.

   Attributes for VCR Controls:

   o  skipinterval - optional, default value "6s": The "skipinterval"
      attribute indicates how far the media server should skip backwards
      or forwards when the rewind key (rwkey) or fast forward key
      (ffkey) is pressed, specified as a time value (Section 4.2.1).

   o  ffkey - optional, no default value: The "ffkey" attribute maps a
      DTMF key to a fast forward operation equal to the value of the
      "skipinterval" attribute.

   o  rwkey - optional, no default value: The "rwkey" attribute maps a
      DTMF key to a rewind action equal to the value of the
      "skipinterval" attribute.

   Clients MUST NOT map the same DTMF digit to both the "rwkey" and
   "ffkey" attributes in a single <playcollect> request.

   VCR control operations are bounded by the beginning and end of the
   prompt sequence.  A rewind action that moves the offset before the
   beginning of the sequence results in playback starting at the
   beginning of the sequence (i.e., offset=0).  A fast forward action
   that moves the offset past the end of the sequence results in the
   media server's treating the sequence as complete.






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6.4.3.  Collection Timers

   MSCML defines several timer attributes that control how long the
   media server waits for digits in the input sequence.  All timer
   settings are time values (Section 4.2.1).  The list below describes
   these attributes and their use.

   Collection Timer Attributes:

   o  firstdigittimer - optional, default value "5000ms": Specifies how
      long the media server waits for the initial DTMF input before
      terminating the collection.  Expressed as a time value (Section
      4.2.1) from 1ms onwards or the strings "immediate" and "infinite."
      The value "immediate" indicates that the timer should fire
      immediately whereas "infinite" indicates that the timer will never
      fire.

   o  interdigittimer - optional, default value "2000ms": Specifies how
      long the media server waits between DTMF inputs.  Expressed as a
      time value (Section 4.2.1) from 1ms onwards or the strings
      "immediate" and "infinite."  The value "immediate" indicates that
      the timer should fire immediately, whereas "infinite" indicates
      that the timer will never fire.

   o  extradigittimer - optional, default value "1000ms": Specifies how
      long the media server waits for additional user input after the
      specified number of digits has been collected.  Expressed as a
      time value (Section 4.2.1) from 1ms onwards or the strings
      "immediate" and "infinite."  The value "immediate" indicates that
      the timer should fire immediately, whereas "infinite" indicates
      that the timer will never fire.

   o  interdigitcriticaltimer - optional, defaults to the value of the
      interdigittimer attribute: Specifies how long the media server
      waits after a grammar has been matched for a subsequent digit that
      may cause a longer match.  Expressed as a time value (Section
      4.2.1) from 1ms onwards or the strings "immediate" and "infinite."
      The value "immediate" results in "shortest match first" behavior,
      whereas "infinite" means to wait indefinitely for additional
      input.  If not explicitly specified otherwise, this attribute is
      set to the value of the 'interdigittimer' attribute.

   The extradigittimer setting enables the "returnkey" input to be
   associated with the current collection.  For example, if maxdigits is
   set to 3 and returnkey is set to #, the user may enter either "x#",
   "xx#", or "xxx#", where x represents a DTMF digit.





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   If the media server detects the "returnkey" pattern during the
   "extradigit" interval, the media server returns the collected digits
   to the client and removes the "returnkey" from the digit buffer.

   If this were not the case, the example would return "xxx" to the
   client and leave the terminating "#" in the digit buffer.  At the
   next <playcollect> request, the media server would process the '#'.
   This might result in the termination of the following prompt, which
   is clearly not what the user intended.

   The extradigittimer has no effect unless returnkey has been set.

6.4.4.  Logging Caller DTMF Input

   Standard SIP mechanisms, such as those discussed in Security
   Considerations (Section 14), protect MSCML protocol exchanges and the
   information they contain.  These protections do not apply to data
   captured in media server log files.  In general, media server logging
   is platform specific and therefore is not covered by this
   specification.  However, one aspect of logging, the capture of
   sensitive information (such as personal identification numbers or
   credit card numbers), is relevant.  The media server has no means to
   determine whether the DTMF input it receives may be sensitive, as
   that is in the purview of the client.  Recognizing this, MSCML
   includes a per-request mechanism to suppress logging of captured DTMF
   to be enabled by clients as needed.

   The "maskdigits" attribute controls whether detected DTMF digits
   appear in the log output.  Clients use this attribute when the media
   server collects sensitive information that should not be accessible
   through the log files.

   Maskdigits Attribute:

   o  maskdigits - optional, default value "no": Controls whether user
      DTMF inputs are captured in media server log files.  The possible
      values for this attribute are "yes" and "no".

6.4.5.  Specifying DTMF Grammars

   MSCML supports four methods for specifying DTMF grammars: the
   "maxdigits" attribute, which provides a simple mechanism for
   collecting any number of digits up to the maximum, regular
   expressions, MGCP [5] digit maps, and H.248.1 [6] digit maps.  A
   media server MUST support the maxdigits and regular expression
   methods for specifying DTMF grammars and SHOULD support MGCP and
   H.248.1 methods.  A client MUST NOT mix DTMF grammar types in a
   single <playcollect> request.



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   Following is a description of the "maxdigits" attribute.

   Maxdigits Attribute:

   o  maxdigits - optional, no default value: Specifies the maximum
      number of DTMF digits to be collected.

   The <pattern> element specifies a digit pattern or patterns for the
   media server to look for.  This element may contain three different
   child elements that specify the type of DTMF grammar used in the
   expression.  The <pattern> element has no attributes.

   <regex> Use regular expressions to define DTMF patterns to match.
      The complete regular expression syntax used in MSCML is described
      in Appendix A.

   <mgcpdigitmap> Use digit maps as specified in MGCP [5].

   <megacodigitmap> Use digit maps as specified in H.248.1 [6].

   At least one <regex> element MUST be present in <pattern> when regex
   grammars are used.  Multiple <regex> elements MAY be present.  When
   <mgcpdigitmap> or <megacodigitmap> grammars are used, <pattern> MUST
   contain only one grammar element.

   The DTMF grammar elements <regex>, <mgcpdigitmap>, and
   <megacodigitmap> have the attributes described in the list below.

   Attributes of DTMF Grammar Elements:

   o  value - required, no default value: Specifies a string
      representing a DTMF grammar matching the parent element type
      (e.g., regex).  Regex values represent a single DTMF grammar.
      MGCP and MEGACO digit maps allow multiple grammars to be described
      in a single string.

   o  name - optional, no default value: Associates a client defined
      name for the grammar that is sent back in the <playcollect>
      response.  This attribute is most useful with regex type grammars
      as each grammar element can have a unique name.

6.4.6.  Playcollect Response

   When the <playcollect> has finished, the media server sends a
   <response> payload to the client in a SIP INFO message.

   Details of the <playcollect> response are described in Section 10.5.




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6.4.7.  Playcollect Example

   The following <playcollect> request (Figure 18) example depicts use
   of the "maxdigits" attribute to control digit collection.

   <?xml version="1.0"?>
   <MediaServerControl version="1.0">
     <request>
       <playcollect id="332986004" maxdigits="6" firstdigittimer="10000"
         interdigittimer="5000" extradigittimer="1000"
         interdigitcriticaltimer="1000" returnkey="#" escapekey="*"
         cleardigits="no" barge="yes" maskdigits="no">
         <prompt baseurl="http://www.example.com/prompts/">
           <audio url="generic/en_US/enter_pin.wav"/>
         </prompt>
       </playcollect>
     </request>
   </MediaServerControl>

   Figure 18: <Playcollect> Request Example Using the Maxdigits
   Attribute

6.5.  Prompt and Record <playrecord>

   The <playrecord> request directs the media server to convert and
   possibly to transcode the RTP payloads it receives and store them to
   the specified URL using the requested content codec(s) and file
   format.  This request proceeds in two phases; prompt and record.

   The <playrecord> request shares the basic attributes of <play> and
   <playcollect> as described in Section 6.3.  MSCML also defines other
   attributes that control the behavior of the prompt and recording
   phases.  These phases and the attributes that control them are
   described in the text and tables below.

6.5.1.  Prompt Phase

   The presence or absence of a "prompturl" attribute or child <prompt>
   element controls whether a prompt is played before recording begins.
   As previously noted, use of the "prompturl" attribute is deprecated,
   and clients SHOULD use <prompt> instead.

   When the client requests that the media server prompt the caller
   before recording audio, <playrecord> has two stages.  The first is
   equivalent to a <playcollect> operation.  The client may set the
   prompt phase to be interruptible by DTMF input (barge) and may
   specify an escape key that will terminate the <playrecord> request
   before the recording phase begins.



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   The list below describes the attributes of <playrecord> that specify
   the behavior of the prompt phase of the request.

   Playrecord Attributes for the Prompt Phase:

   o  barge - optional, default value "yes": Specifies whether user
      input will barge the prompt and force transition to the record
      phase.  When it is set to "yes", a DTMF input will barge the
      prompt.  When it is set to "no", the prompt phase cannot be
      barged, and any user input during the prompt is placed in the
      quarantine buffer for inspection during the collect phase.  Note
      that if the "barge" attribute is set to "no", the "cleardigits"
      attribute implicitly has a value of "yes".  This ensures that the
      media server does not leave DTMF input that occurred prior to the
      current collection in the quarantine buffer after the request
      completes.

   o  cleardigits - optional, default value "no": Specifies whether
      previous user input should be considered or ignored for barge-in
      purposes.  When it is set to "yes", any previously buffered digits
      are removed, so prior user input is ignored.  If it is set to
      "no", previously buffered digits will be considered.  If
      "cleardigits" is set to "no" and barge-in is enabled, previously
      buffered digits will terminate the prompt phase immediately.  In
      this case, the prompt is not played, and recording begins
      immediately.

   o  escapekey - optional, default value "*": Specifies a DTMF key that
      indicates the user wishes to terminate the current operation
      without saving any input recorded to that point.  Detection of the
      mapped DTMF key terminates the request immediately and generates a
      response.

   Detection of the escape key generates a response message, and the
   operation returns immediately.  If the user presses any other keys
   and if the prompt is interruptible (barge="yes"), then the play stops
   immediately, and the recording phase begins.

6.5.2.  Record Phase

   If the request proceeds to the recording phase, the media server
   discards any digits from the collect phase from the quarantine buffer
   to eliminate unintended termination of the recording.  The following
   attributes control recording behavior.

   Playrecord Attributes for the Record Phase:





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   o  recurl - required, no default value: Specifies the target URL for
      the recorded content.

   o  recencoding - optional, default value "ulaw": Specifies the
      encoding of the recorded content if it cannot be inferred from the
      recurl.  Possible values are "ulaw", "alaw", and "msgsm."

   o  mode - optional, default value "overwrite": Specifies whether the
      recording should overwrite or be appended to the target URL.
      Allowable values are "overwrite" and "append."

   o  duration - optional, default value "infinite": Specifies the
      maximum allowable duration for the recording.  Expressed as a time
      value (Section 4.2.1) from 1 onwards or the strings "immediate"
      and "infinite."  The value "immediate" indicates that recording
      will end immediately, whereas "infinite" indicates recording
      should continue indefinitely.  If the maximum duration is reached,
      the <playrecord> request will terminate and generate a response.

   o  beep - optional, default value "yes": Specifies whether a beep
      should be played to the caller immediately prior to the start of
      the recording phase.  Allowable values are "yes" and "no."

   o  initsilence - optional, default value "3000ms": Specifies how long
      to wait for initial speech input before terminating (canceling)
      the recording.  Expressed as a time value (Section 4.2.1) from 1ms
      onwards or the strings "immediate" and "infinite."  The value
      "immediate" indicates that the timer should fire immediately,
      whereas "infinite" directs the media server to wait indefinitely.

   o  endsilence - optional, default value "4000ms": Specifies how long
      the media server waits after speech has ended to stop the
      recording.  Expressed as a time value (Section 4.2.1) from 1ms
      onwards or the strings "immediate" and "infinite."  When set to
      "infinite", the recording will continue indefinitely after speech
      has ended and will only terminate due to a DTMF keypress or
      because the input has reached the maximum desired duration.

   o  recstopmask - optional, default value "0123456789ABCD#*":
      Specifies a list of individual DTMF characters that, if detected,
      will cause the recording to be terminated.  To ensure that the
      input of a specific key does not cause the recording to stop,
      remove the DTMF key from the list.

   Media servers MUST support local and remote (NFS) "file://" scheme
   URLs in the "recurl" attribute.  MSCML supports "http://" and
   "https://" scheme URLs indirectly through the <managecontent>
   (Section 8) request.



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   The media server buffers and returns any digits collected in the
   prompt phase, with the exception of those contained in the
   "recstopmask" attribute, in the response.

   The media server compares digits detected during the recording phase
   to the digits specified in the "recstopmask" to determine whether
   they indicate a recording termination request.

   The media server ignores digits not present in the recstopmask and
   passes them into the recording.  If DTMF input terminates the
   recording, the media server returns the collected digit to the client
   in the <response>.

   Once recording has begun, the media server writes the received media
   to the specified recurl URL no matter what DTMF events the media
   server detects.  It is the responsibility of the client to examine
   the DTMF input returned in the <response> message to determine
   whether the audio file should be saved or deleted and, potentially,
   re-recorded.

   If the endsilence timer expires, the media server trims the end of
   the recorded audio by an amount equal to the value of the
   "endsilence" attribute.

   When the recording is finished, the media server generates a
   <response> message and sends it to the client in a SIP INFO message.
   Details of the <playrecord> response are described in Section 10.6.

6.5.3.  Playrecord Example

   The recording example (Figure 19) plays a prompt and records it to
   the destination specified in the "recurl" attribute encoded as MS-GSM
   in wave format.


















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   <?xml version="1.0"?>
   <MediaServerControl version="1.0">
     <request>
       <playrecord id="5556123"
         recurl="file:////nfs.example.com/rec/name.wav"
         recencoding="msgsm"
         initsilence="5000" endsilence="3000" duration="30000"
         barge="yes"
         beep="yes"
         mode="overwrite"
         cleardigits="no"
         escapekey="*"
         recstopmask="0123456789#*">
         <prompt>
           <audio url="http://www.example.com/prompts/recordname.wav"/>
         </prompt>
       </playrecord>
     </request>
   </MediaServerControl>

   Figure 19: Recording Example

6.6.  Stop Request <stop>

   The client issues a <stop> request when the objective is to stop a
   request in progress and not to initiate another operation.  This
   request generates a <response> message from the media server.

   The only attribute is id, which is optional.

   The client-defined request id correlates the asynchronous response
   with its original request and echoes back to the client in the media
   server's response.

   The following MSCML payload (Figure 20) depicts an example <stop>
   request.

   <?xml version="1.0"?>
   <MediaServerControl version="1.0">
     <request>
       <stop id="4578903"/>
     </request>
   </MediaServerControl>

   Figure 20: Stop Example

   The format of a response to a <stop> request is detailed in Section
   10.2.



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   As discussed previously, the media server treats a SIP re-INVITE that
   modifies the established SDP parameters as an implicit <stop>
   request.  Examples of such SDP modifications include receiving hold
   SDP or removing an audio or video stream.  When this occurs, the
   media server immediately terminates the running <play>,
   <playcollect>, or <playrecord> request and sends a <response>
   indicating "reason=stopped".

7.  Call Leg Events

   MSCML defines event notifications that are scoped to a specific SIP
   dialog or call leg.  These events allow a client to be notified of
   individual, asynchronous DTMF keypresses, as well as of various call
   progress signals.  The subscription, event detection, and
   notifications for call leg events occur in the same SIP dialog.  This
   is different from the conference level active talker events described
   earlier.  The subscription and notifications for active talker events
   occur on the conference control leg, but the actual event detection
   occurs on one or more participant legs.

   Subscriptions for call leg events are made by sending an MSCML
   <configure_leg> request on the desired SIP dialog.  Call leg events
   may be used with the MSCML conferencing or IVR services.  When used
   with the IVR service, the <configure_leg> request SHOULD NOT include
   any conference-related attributes.  The media server MUST ignore
   these if present.  Call leg event subscriptions MUST NOT be made on
   the conference control leg, since it has no actual RTP media to
   process for event detection.  The media server MUST reject a
   <configure_leg> request sent on the conference control leg.

   The <configure_leg> request contains the child elements <subscribe>
   and <events>.  The <events> element may contain two child elements
   that control subscriptions to call leg events.  These are <keypress>
   and <signal>.  A <configure_leg> request MUST contain at most one
   <keypress> element but MAY contain multiple <signal> elements that
   request notification of different call progress events.

7.1.  Keypress Events

   Keypress events are used when the client wishes to receive
   notifications of individual DTMF events that are not tied to a
   specific <playcollect> request.  One use of this facility is to
   monitor conference legs for DTMF inputs that require application
   intervention; for example, to notify the moderator that the caller
   wishes to speak.  Keypress events are also used when the application
   desires complete control of grammars and timing constraints.





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   When used in a subscription context, the <keypress> element has two
   attributes, 'report' and 'maskdigits', which are detailed in the list
   below.

   Keypress Subscription Attributes:

   o  report - required, no default value: Possible values are
      'standard', 'long', 'both', and 'none'.  'Standard' means that
      detected digits should be reported.  'Long' means that long digits
      should be reported.  'Long' digits are defined as a single key
      press held down for more than one second, or two distinct key
      presses (a "double") of the same digit that occur within two
      seconds of each other with no other intervening digits.  'Both'
      means that both 'standard' and 'long' digit events should be
      reported.  As a 'long' digit consists of one or more "normal"
      digits, a single long duration key press will generate one
      standard event and one 'long' event.  A "double" will produce two
      standard events and one 'long' event.  'None' means that no
      keypress events should be reported; it disables keypress event
      reporting if enabled.

   o  maskdigits - optional, default value "no": Controls whether user
      DTMF inputs are captured in media server log files.  The possible
      values for this attribute are "yes" and "no".

   The media server sends an MSCML response to the subscription
   immediately upon receiving the request.  Notifications are sent to
   the client when the specified events are detected.

   When used in a notification context, the <keypress> element has
   several attributes that are used to convey details of the event that
   was detected.  It also contains a child element, <status>, that
   provides information on any MSCML request that was in progress when
   the event occurred.  The details of these notification attributes are
   described in the list below.

   Keypress Notification Attributes:

   o  digit - required, no default value: Specifies the DTMF digit
      detected.  Possible values are [0-9], [A-D], '#', or '*'.

   o  length - required, no default value: Specifies the duration class
      of the DTMF input.  Possible values are 'standard' or 'long'.

   o  method - required, no default value: Specifies the keypress
      detection method that generated the notification.  Possible values
      are 'standard', 'long', and 'double'.




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   o  interdigittime - required, no default value: Specifies the elapsed
      time, as a time value (Section 4.2.1), between the current event
      detection and the previous one.

7.1.1.  Keypress Subscription Examples

   The following examples of MSCML payloads depict a subscription for
   standard keypress events and disabling keypress reporting.

   Figure 21 shows a subscription for standard keypress events.

   <?xml version="1.0"?>
   <MediaServerControl version="1.0">
     <request>
       <configure_leg>
         <subscribe>
           <events>
             <keypress report="standard"/>
           </events>
         </subscribe>
       </configure_leg>
     </request>
   </MediaServerControl>

   Figure 21: Standard Digit Events Subscription

   Figure 22 shows a client disabling keypress event notifications.

   <?xml version="1.0"?>
   <MediaServerControl version="1.0">
     <request>
       <configure_leg>
         <subscribe>
           <events>
             <keypress report="none"/>
           </events>
         </subscribe>
       </configure_leg>
     </request>
   </MediaServerControl>

   Figure 22: Disabling Keypress Event Reporting

7.1.2.  Keypress Notification Examples

   The following MSCML payloads depict keypress event notifications
   caused by various types of DTMF input.




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   Figure 23 shows a notification generated by the detection of a
   standard "4" DTMF digit.  In this example, this is the first digit
   detected.  Thus, the 'interdigittime' attribute has a value of '0'.

   <?xml version="1.0"?>
   <MediaServerControl version="1.0">
     <notification>
       <keypress digit="4" length="standard" method="standard"
         interdigittime="0">
         <status command="play" duration="10"/>
       </keypress>
     </notification>
   </MediaServerControl>

   Figure 23: Standard Keypress Notification

   Figure 24 shows a notification generated by detection of a long pound
   (#).

   <?xml version="1.0"?>
   <MediaServerControl version="1.0">
     <notification>
       <keypress digit="#" length="long" method="long"
         interdigittime="200">
         <status command="idle" duration="4"/>
       </keypress>
     </notification>
   </MediaServerControl>

   Figure 24: Long Keypress Notification

7.2.  Signal Events

   MSCML supports notification of certain call progress tones through
   the <signal> element.  When used in a subscription context, the
   <signal> element has two attributes, 'type' and 'report', and no
   child elements.  These attributes are detailed in the list below.

   Signal Subscription Attributes:

   o  report - required, no default value: Controls whether the
      specified signal is reported.  Possible values are 'yes' and 'no'.
      When set to 'yes', the media server invokes the required signal
      detection code and reports detected events.  When it is set to
      'no', the media server disables the associated signal detection
      code and does not report events.





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   o  type - required, no default value: Specifies the type of call
      progress signal to detect.  Possible values are 'busy', 'ring',
      'CED', 'CNG', and '400', which correspond to busy tone, ring tone,
      fax CED, fax CNG, and 400 Hz tone, respectively.

      NOTE: The details of media server provisioning required to support
      country-specific variants of 'busy' and 'ring' is not covered by
      this specification.

   As stated previously, a single <configure_leg> request MAY contain
   multiple <signal> elements that request notification of different
   call progress tones.  A single <configure_leg> request SHOULD NOT
   contain multiple <signal> elements that have the same 'type'
   attribute value.  If the media server receives such a request, it
   SHOULD honor the last element specifying that type that appears in
   the request.

   The media server generates an immediate response to the
   <configure_leg> subscription request and sends notifications when the
   specified signals are detected.  A single notification is sent as
   soon as the specified signal has been reliably detected.  If the
   signal persists continuously, additional notifications will not be
   sent.  If the signal is interrupted and then resumes, additional
   notifications will be sent.

   Signal notifications have a single attribute, "type", as described in
   the list below.

   Signal Notification Attribute:

   o  type - required, no default value: Specifies the type of call
      progress signal that was detected.  Possible values are 'busy',
      'ring', 'CED', 'CNG', and '400', which correspond to busy tone,
      ring tone, fax CED, fax CNG, and 400 Hz tone, respectively.

7.2.1.  Signal Event Examples

   The following MSCML payloads show a signal event subscription (Figure
   25) and notification (Figure 26).












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   <?xml version="1.0"?>
   <MediaServerControl version="1.0">
     <request>
       <configure_leg>
         <subscribe>
           <events>
             <signal type="busy" report="yes"/>
           </events>
         </subscribe>
       </configure_leg>
     </request>
   </MediaServerControl>

   Figure 25: Signal Event Subscription

   <?xml version="1.0"?>
   <MediaServerControl version="1.0">
     <notification>
       <signal type="busy"/>
     </notification>
   </MediaServerControl>

   Figure 26: Signal Event Notification

8.  Managing Content <managecontent>

   MSCML uses the <managecontent> request to move recorded content from
   the media server to remote locations using the HTTP protocol.  This
   is a store-and-forward model, which requires the completion of local
   temporary recording before the media server can send it to the web
   server.  This facility is useful in applications such as voice
   messaging, where a message may be reviewed by the caller prior to
   being committed to persistent storage.

   The <managecontent> request contains no child elements and has the
   attributes described in the list below.

   Managecontent Attributes:

   o  src - required, no default value: Specifies the local source URL
      of the content.  The URL scheme MUST be "file://".

   o  dest - required (see note), no default value: Specifies the
      destination URL.  The URL scheme MUST be "http://".  Note: If the
      selected action is 'delete', this attribute is optional; otherwise
      it is required.





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   o  action - optional, default value "move": Specifies the operation
      for the media server to execute.  Values can be either 'move' or
      'delete'.  The 'delete' action operates on the local source file.
      After a successful move or delete, the media server deletes the
      source file from its local storage.  If the request is
      unsuccessful, the source file is not deleted, which gives the
      client complete control of the retry strategy.

   o  httpmethod - optional, default value "post": HTTP protocol method
      for the media server to use in the HTTP request.  The only values
      are 'post' or 'put'.

   o  name - required (see note), no default value: Specifies the field
      name for the content in the form when using the 'post' method.
      This is not to be confused with the "src" or "dest" attributes.
      Note: This attribute is required when the "htttpmethod" has the
      value "post" and is optional otherwise.

   o  fetchtimeout - optional, default value "10000ms": Specifies the
      maximum time allowed for the transfer to complete.  Expressed as a
      time value (Section 4.2.1) from 1ms onwards.

   o  mimetype - required (see note), no default value: Specifies the
      MIME type that the media server will use for the content transfer.
      If it is not provided, the media server MUST try to infer it from
      the content file extension based on a platform specific mapping
      table.  A non-normative, example mapping table is shown in Table
      3.  To avoid ambiguity, we RECOMMEND that clients explicitly set
      this attribute.  Note: If the MIME type of the content cannot be
      inferred from the file extension, this attribute is required.

   Table 3 shows common audio and video MIME types and possible file
   extension mappings.


















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                    +-----------+--------------------+
                    | Extension | MIME Type          |
                    +-----------+--------------------+
                    | alaw      | audio/x-alaw-basic |
                    | ulaw      | audio/basic        |
                    | msgsm     | audio/ms-gsm       |
                    | wav       | audio/x-wav        |
                    | tif       | image/tiff         |
                    | tiff      | image/tiff         |
                    | mov       | video/quicktime    |
                    | qt        | video/quicktime    |
                    | 3gp       | video/3gpp         |
                    | 3gpp      | video/3gpp         |
                    +-----------+--------------------+

           Table 3: Example File Extension to MIME Type Mappings

   <Managecontent> is purely a transport operation; the underlying
   content is not changed by it.  Therefore clients MUST ensure that the
   source and destination file name extensions and MIME types are the
   same.  Failure to do so could result in content that is unreadable.

   The ability to move or delete any local file presents a potential
   risk to the security of the media server system.  For this reason, we
   STRONGLY RECOMMEND that implementers limit local file system access
   when using <managecontent>.  For example, we encourage limiting
   access as based on file ownership and/or specific directories.

8.1.  Managecontent Example

   The following is an example (Figure 27) showing a local file on the
   media server being transferred to an HTTP URL using the "put" method.
   The client sends the following request.

   <?xml version="1.0"?>
   <MediaServerControl version="1.0">
     <request>
       <managecontent id="102"
       src="file:////var/mediaserver/rec/6A5GH49B.ulaw"
       dest="http://www.example.com/recordings/myrecording.ulaw"
       mimetype="audio/basic" action="move" httpmethod="put"
       fetchtimeout="5000"/>
     </request>
   </MediaServerControl>

   Figure 27: Managecontent Example





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   Note that the client can change the temporary file name assigned by
   the media server as part of this operation as shown.

   If the request is ambiguous, the media server MUST return a status
   code of "400" and text "Bad Request."  If the media server is unable
   to execute a syntactically correct and unambiguous request, it MUST
   return a "500" status code with the text "Server Error."  For
   example, the local file system access restrictions may prevent
   deletion of the specified file.  In this case, the "reason" attribute
   in the response conveys additional details on the server error that
   occurred.  If there is a network or remote server error, the media
   server provides detailed error information in the <error_info>
   element contained in the media server response.  Additional
   information regarding <managecontent> responses is provided in
   Section 10.7.

9.  Fax Processing

9.1.  Recording a Fax <faxrecord>

   The <faxrecord> request directs the media server to process a fax in
   answer mode.  The reason for a request separate from <playrecord> is
   that the media server needs to know to process the T.30 [18] or T.38
   [19] fax protocols.

   The <faxrecord> request has multiple attributes and one child
   element, <prompt>.  Its attributes are described in the list below.

   Attributes of <faxrecord>:

   o  lclid - optional, default value "" (the empty string): A string
      that identifies the called station.

   o  prompturl - optional, no default value: The URL of the fax content
      to be retrieved and played.  The target may be a local or remote
      (NFS) "file://" scheme URL or an "http://" or "https://" scheme
      URL.  NOTE: Use of this attribute is deprecated.

   o  promptencoding - optional, no default value: Specifies the content
      encoding for files that do not have a 'tif' or 'tiff' extension.
      The only allowable value is 'tiff'.  This attribute only affects
      "file://" scheme URLs.  NOTE: Use of this attribute is deprecated.

   o  recurl - optional, no default value: Specifies the target URL for
      the recorded content.

   o  rmtid - optional, no default value: Specifies the calling station
      identifier of the remote terminal.  If present, the media server



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      MUST reject transactions with the remote terminal if the remote
      terminal's identifier does not match the value of 'rmtid'.

   Clients SHOULD use the more flexible <prompt> mechanism for
   specifying fax content.  Use of the 'prompturl' attribute is
   deprecated and may not be supported in future MSCML versions.  The
   <prompt> element is described in Section 6.1.1.  A <prompt> element
   sent in a <faxrecord> request MUST NOT contain <variable> elements.

   Media servers MUST support local and remote (NFS) "file://" scheme
   URLs in the "recurl" attribute.  MSCML supports "http://" and
   "https://" scheme URLs indirectly through the <managecontent>
   (Section 8) request.

   The <faxrecord> request operates in one of three modes: receive,
   poll, and turnaround poll.  The combination of <prompt> or
   'prompturl' attribute and 'recurl' attribute define the mode.  Table
   4 describes these modes in detail.  The 'prompt' column in the table
   has the value 'yes' if the request has either a <prompt> element or a
   'prompturl' attribute.

   +--------+--------+---------+---------------------------------------+
   | prompt | recurl | Mode    | Operation                             |
   +--------+--------+---------+---------------------------------------+
   | no     | no     | Invalid | Request fails.                        |
   | no     | yes    | Receive | Record the fax to the target URL      |
   |        |        |         | specified in 'recurl'.                |
   | yes    | no     | Poll    | Send fax from source specified in the |
   |        |        |         | <prompt> element or 'prompturl'       |
   |        |        |         | attribute.  If there is a 'rmtid', it |
   |        |        |         | MUST match the remote terminal's      |
   |        |        |         | identifier, or the request will fail. |
   | yes    | yes    | TP      | Turnaround Poll (TP) mode. If the     |
   |        |        |         | remote terminal wishes to transmit,   |
   |        |        |         | the media server records the fax to   |
   |        |        |         | the target URL specified in 'recurl'. |
   |        |        |         | If the remote terminal wishes to      |
   |        |        |         | receive, the media server sends the   |
   |        |        |         | fax from the source URL contained in  |
   |        |        |         | <prompt> or 'prompturl'.  If there is |
   |        |        |         | a 'rmtid', it MUST match remote       |
   |        |        |         | terminal's identifier, or the send    |
   |        |        |         | request will fail.  A receive         |
   |        |        |         | operation will still succeed,         |
   |        |        |         | however.                              |
   +--------+--------+---------+---------------------------------------+

                        Table 4: Fax Receive Modes



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   In receive mode, the media server receives the fax and writes the fax
   data to the target URL specified by the 'recurl' attribute.

   In poll mode, the media server sends a fax, but as a polled (called)
   device.

   In turnaround poll mode, the media server will record a fax that the
   remote machine sends.  If the remote machine requests a transmission,
   then the media server will send the fax.

   When transmitting a fax, the media server will advertise that it can
   receive faxes in the DIS message.  Likewise, when receiving a fax,
   the media server will advertise that it can send faxes in the DIS
   message.

   The media server MUST flush any quarantined digits when it receives a
   <faxrecord> request.

9.2.  Sending a Fax <faxplay>

   The <faxplay> request directs the media server to process a fax in
   originate mode.  The reason for a request separate from <play> is
   that the media server needs to know to process the T.30 [18] or T.38
   [19] fax protocols.

   The <faxplay> request has multiple attributes and one child element,
   <prompt>.  Its attributes are described in the list below.

   Attributes of <faxplay>:

   o  lclid - optional, default value "" (the empty string): A string
      that identifies the called station.

   o  prompturl - optional, no default value: The URL of the content to
      be retrieved and played.  The target may be a local or remote
      (NFS) "file://" scheme URL or an "http://" or "https://" scheme
      URL.  NOTE: Use of this attribute is deprecated.

   o  promptencoding - optional, no default value: Specifies the content
      encoding for files that do not have a 'tif' or 'tiff' extension.
      The only allowable value is 'tiff'.  This attribute only affects
      "file://" scheme URLs.  NOTE: Use of this attribute is deprecated.

   o  recurl - optional, no default value: Specifies the target URL for
      the recorded content.

   o  rmtid - optional, no default value: Specifies the calling station
      identifier of the remote terminal.  If present, the media server



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      MUST reject transactions with the remote terminal if the remote
      terminal's identifier does not match the value of 'rmtid'.

   Clients SHOULD use the more flexible <prompt> mechanism for
   specifying fax content.  Use of the 'prompturl' attribute is
   deprecated and may not be supported in future MSCML versions.  The
   <prompt> element is described in Section 6.1.1.  A <prompt> element
   sent in a <faxrecord> request MUST NOT contain <variable> elements.

   Media servers MUST support local and remote (NFS) "file://" scheme
   URLs in the "recurl" attribute.  MSCML supports "http://" and
   "https://" scheme URLs indirectly through the <managecontent>
   (Section 8) request.

   The <faxplay> request operates in one of three modes: send, remote
   poll, and turnaround poll.  The combination of <prompt> or
   'prompturl' attribute and 'recurl' attribute define the mode.  Table
   5 describes these modes in detail.  The 'prompt' column in the table
   has the value 'yes' if the request has either a <prompt> element or a
   'prompturl' attribute.































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   +--------+--------+---------+---------------------------------------+
   | prompt | recurl | Mode    | Operation                             |
   +--------+--------+---------+---------------------------------------+
   | no     | no     | Invalid | Request fails.                        |
   | yes    | no     | Send    | Send fax from source specified in the |
   |        |        |         | <prompt> element or 'prompturl'       |
   |        |        |         | attribute. If there is a 'rmtid', it  |
   |        |        |         | MUST match the remote terminal's      |
   |        |        |         | identifier, or the request will fail. |
   | no     | yes    | Poll    | Send fax from source specified in the |
   |        |        |         | <prompt> element or 'prompturl'       |
   |        |        |         | attribute, assuming the remote        |
   |        |        |         | terminal specifies it can receive a   |
   |        |        |         | fax in its DIS message. If the remote |
   |        |        |         | terminal does not support reverse     |
   |        |        |         | polling, the request will fail. If    |
   |        |        |         | 'rmtid' is specified, it MUST match   |
   |        |        |         | remote terminal's identifier, or the  |
   |        |        |         | request will fail.                    |
   | yes    | yes    | TP      | Turnaround Poll (TP) mode. If the     |
   |        |        |         | remote terminal wishes to transmit,   |
   |        |        |         | the media server records the fax to   |
   |        |        |         | the target URL specified in 'recurl'. |
   |        |        |         | If the remote terminal wishes to      |
   |        |        |         | receive, the media server sends the   |
   |        |        |         | fax from the source URL contained in  |
   |        |        |         | <prompt> or 'prompturl'. If there is  |
   |        |        |         | a 'rmtid', it MUST match remote       |
   |        |        |         | terminal's identifier, or the send    |
   |        |        |         | request will fail. A receive          |
   |        |        |         | operation will still succeed,         |
   |        |        |         | however.                              |
   +--------+--------+---------+---------------------------------------+

                          Table 5: Fax Send Modes

   In send mode, the media server sends the fax.

   In remote poll mode, the client places a call on behalf of the media
   server.  The media server requests a fax transmission from the remote
   fax terminal.

   In turnaround poll mode, the media server will record a fax that the
   remote machine sends.  If the remote machine requests a transmission,
   then the media server will send the fax.

   When transmitting a fax, the media server will advertise that it can
   receive faxes in the DIS message.  Likewise, when receiving a fax,



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   the media server will advertise that it can send faxes in the DIS
   message.

   The media server MUST flush any quarantined digits when it receives a
   <faxplay> request.

10.  MSCML Response Attributes and Elements

10.1.  Mechanism

   The media server acknowledges receipt of a client MSCML request sent
   in a SIP INVITE by sending a response of either 200 OK or 415 Bad
   Media Type.  The media server responds with 415 when the SIP request
   contains a content type other than "application/sdp" or "application/
   mediaservercontrol+xml".

   The media server acknowledges receipt of a client MSCML request sent
   in a SIP INFO with a 200 OK or 415 Bad Media Type.  The media server
   responds with 415 if the INFO request contains a content type other
   than "application/mediaservercontrol+xml".

   The media server transports the MSCML <response> message in a SIP
   INFO request.

   If there is an error in the request or the media server cannot
   complete the request, the media server sends the <response> message
   very shortly after receiving the request.  If the request is able to
   proceed, the <response> contains final status information as
   described below.

10.2.  Base <response> Attributes

   All MSCML responses have the basic attributes defined in the list
   below.

   Basic MSCML Response Attributes:

   o  id - optional, no default value: Echoes the client-defined ID
      contained in the request.

   o  request - required, no default value: Specifies the MSCML request
      type that generated the response.  Allowable values are
      "configure_conference", "configure_leg", "play", "playcollect",
      "playrecord", "stop", "faxplay", "faxrecord", and "managecontent".







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   o  code - required, no default value: The final status code for the
      request.  MSCML uses a subset of the status classes defined in RFC
      3261 [4].  In MSCML, 2XX responses indicate success, 4XX responses
      indicate client error, and 5XX responses indicate an error on the
      media server.  There are no 1XX, 3XX, or 6XX status codes in
      MSCML.

   o  text - required, no default value: The human readable reason
      phrase associated with the status code.

   Responses to <configure_conference> and <stop> requests contain only
   the attributes above.  MSCML responses to other requests MAY contain
   additional request-specific attributes and elements.  These are
   described in the following sections.

10.3.  Response Attributes and Elements for <configure_leg>

   Responses to <configure_leg> requests have only the base response
   attributes defined in Section 10.2.  However, when the request
   contains a <configure_team> element, the response includes a <team>
   element describing the teammate configuration for that leg.  The
   attributes of the <team> element are shown in the list below.

   Attributes of <team>:

   o  id - required, no default value: The client-defined unique
      identifier for the conference leg.

   o  numteam - required, no default value: The number of team members
      for the leg.

   Additional information on each team member is conveyed by child
   <teammate> elements contained within <team>.  Each teammate is
   represented by a single element in the list.  The <teammate> element
   has a single attribute, as described below.

   Attributes of <teammate>:

   o  id - required, no default value: The client-defined unique
      identifier for the teammate leg.

10.4.  Response Attributes and Elements for <play>

   In addition to the base response attributes defined in Section 10.2,
   responses to <play> requests have the additional attributes described
   in the list below.





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   MSCML Response Attributes for <play>:

   o  reason - optional, no default value: For requests that are not
      completed immediately, the "reason" attribute conveys additional
      information regarding why the command was completed.  Possible
      values are "stopped", indicating that an explicit or implicit
      <stop> request was received, and "EOF", indicating that the end of
      the specified sequence of URLs was reached.

   o  playduration - required, no default value: A time value (Section
      4.2.1) that returns the duration of the associated content
      playout.

   o  playoffset - required, no default value: A time value (Section
      4.2.1) that returns the time offset into the specified content
      sequence where play was terminated.  If the initial "offset" value
      in the sequence was "0", then "playduration" and "playoffset" are
      equal.  However, if the initial offset had some other value,
      "playoffset" serves as a bookmark for the client to resume play in
      a subsequent request.

10.4.1.  Reporting Content Retrieval Errors

   If the associated request set "stoponerror=yes" in <prompt> and an
   error occurred while retrieving the specified content the response
   will include an <error_info> element detailing the problem.  This
   element contains the response information received from the remote
   content server.  The <error_info> element has the attributes
   described in the list below.

   Attributes of <error_info>:

   o  code - required, no default value: The status code returned by the
      remote content server.  For example, a web server might return 404
      to indicate that the requested content was not found.

   o  text - required, no default value: The human-readable reason
      phrase returned by the remote content server.  For example, the
      reason phrase "Not Found" would be returned if the requested
      content was not found.

   o  context - required, no default value: Contains the content URL
      that was being fetched when the retrieval error occurred.  This
      enables the client to know precisely which URL in a sequence
      caused the problem.

   An <error_info> element MAY be present in the response to any request
   that contains a child <prompt> element.



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10.5.  Response Attributes and Elements for <playcollect>

   In addition to the base response attributes defined in Section 10.2,
   responses to <playcollect> requests have the additional attributes
   described in the list below.

   MSCML Response Attributes for <playcollect>:

   o  reason - optional, no default value: For requests that are not
      completed immediately, the "reason" attribute conveys additional
      information regarding why the command was completed.  Possible
      values are "stopped", indicating that an explicit or implicit
      <stop> request was received; "match", meaning that a DTMF grammar
      was matched; "timeout", indicating that no DTMF input was received
      before one of the collection timers expired; and "returnkey" or
      "escapekey", meaning the DTMF digit mapped to that key was
      detected and the return key or escape key terminated the
      operation, respectively.

   o  playduration - required, no default value: A time value (Section
      4.2.1) that returns the duration of the associated content
      playout.  If the caller barged the prompt, this value will reflect
      the play duration up to that event.

   o  playoffset - required, no default value: A time value (Section
      4.2.1) that returns the time offset into the specified content
      sequence where play was terminated.  If the initial "offset" value
      in the sequence was "0", then "playduration" and "playoffset" are
      equal.  However, if the initial offset had some other value,
      "playoffset" serves as a bookmark for the client to resume play in
      a subsequent request.  If the caller barged the prompt this value
      will reflect the time offset at which barge-in occurred.

   o  digits - required, no default value: Contains the collected DTMF
      input characters.  If no DTMF input was collected, this attribute
      is set to the empty string ("").

   o  name - required (see note), no default value: The client-defined
      name of the DTMF grammar that was matched.  Note: This attribute
      is required if the "name" attribute was set in the matching DTMF
      grammar.

   Responses to <playcollect> requests MAY include an <error_info>
   element, as described in Section 10.4.1.







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10.6.  Response Attributes and Elements for <playrecord>

   In addition to the base response attributes defined in Section 10.2,
   responses to <playrecord> requests have the additional attributes
   described in the list below.

   o  reason - optional, no default value: For requests that are not
      completed immediately, the "reason" attribute conveys additional
      information regarding why the command was completed.  Possible
      values are "stopped", indicating that an explicit or implicit
      <stop> request was received; "digit", meaning that a DTMF digit
      was detected and that the prompt phase was barged; "init_silence",
      meaning the recording terminated because of no input;
      "end_silence", meaning that the recording was terminated because
      the "endsilence" timer elapsed; "max_duration", indicating that
      the maximum time for the recording was reached; "escapekey",
      indicating that the DTMF input mapped to "escapekey" was detected,
      thus terminating the recording; and "error", indicating a general
      operation failure.

   o  playduration - required, no default value: A time value (Section
      4.2.1) that returns the duration of the associated content
      playout.  If the caller barged the prompt, this value will reflect
      the play duration up to that event.

   o  playoffset - required, no default value: A time value (Section
      4.2.1) that returns the time offset into the specified content
      sequence where play was terminated.  If the initial "offset" value
      in the sequence was "0", then "playduration" and "playoffset" are
      equal.  However, if the initial offset had some other value,
      "playoffset" serves as a bookmark for the client to resume play in
      a subsequent request.  If the caller barged the prompt this value
      will reflect the time offset at which barge-in occurred.

   o  digits - required, no default value: Contains the DTMF digit that
      terminated the recording.  If no DTMF input was detected, this
      attribute is set to the empty string ("").

   o  reclength - required, no default value: The length of the recorded
      content, in bytes.

   o  recduration - required, no default value: A time value (Section
      4.2.1) indicating the elapsed duration of the recording.

   Responses to <playrecord> requests MAY include an <error_info>
   element, as described in Section 10.4.1.





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10.7.  Response Attributes and Elements for <managecontent>

   Responses to <managecontent> requests have only the base response
   attributes defined in Section 10.2.  If a content transfer error
   occurs while executing the request the response will also contain an
   <error_info> element as described in Section 10.4.1.

10.8.  Response Attributes and Elements for <faxplay> and <faxrecord>

   In addition to the base response attributes defined in Section 10.2,
   responses to <faxplay> and <faxrecord> requests have the additional
   attributes described in the list below.

   o  reason - required, no default value: For requests that are not
      completed immediately, the "reason" attribute conveys additional
      information regarding why the command was completed.  Possible
      values are "stopped", indicating that an explicit or implicit
      <stop> request was received; "complete", indicating successful
      completion, even if there were bad lines or minor negotiation
      problems (e.g., a DCN was received); "disconnect", meaning that
      the session was disconnected; and "notfax", indicating that no DIS
      or DCS was received on the connection.

   o  pages_received - required (see note), no default value: Indicates
      the number of fax pages received.  Note: This attribute is
      required if any pages were received.

   o  pages_sent - required (see note), no default value: Indicates the
      number of fax pages sent.  Note: This attribute is required if any
      pages were sent.

   o  faxcode - required, no default value: The value of the "faxcode"
      attribute is the binary-or of the bit patterns defined in Table 6.


















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              +------+--------------------------------------+
              | Mask | description                          |
              +------+--------------------------------------+
              | 0    | Operation Failed                     |
              | 1    | Operation Succeeded                  |
              | 2    | Partial Success                      |
              | 4    | Image received and placed in recurl  |
              | 8    | Image sent from specified source URL |
              | 16   | rmtid did not match                  |
              | 32   | Error reading source URL             |
              | 64   | Error writing recurl                 |
              | 128  | Negotiation failure on send phase    |
              | 256  | Negotiation failure on receive phase |
              | 512  | Reserved                             |
              | 1024 | Irrecoverable IP packet loss         |
              | 2048 | Line errors in received image        |
              +------+--------------------------------------+

                           Table 6: Faxcode Mask

   Responses to <faxplay> and <faxrecord> requests MAY include an
   <error_info> element, as described in Section 10.4.1.

11.  Formal Syntax

   The following syntax specification uses XML Schema as described in
   XML [7].

11.1.  Schema

   <?xml version="1.0" encoding="UTF-8"?>
   <xs:schema xmlns:xs="http://www.w3.org/2001/XMLSchema"
     elementFormDefault="qualified">
     <xs:element name="MediaServerControl">
       <xs:complexType>
         <xs:choice>
           <xs:element name="request">
             <xs:complexType>
               <xs:choice>
                 <xs:element name="configure_conference"
                   type="configure_conferenceRequestType"/>
                 <xs:element name="configure_leg"
                   type="configure_legRequestType"/>
                 <xs:element name="play" type="playRequestType"/>
                 <xs:element name="playcollect"
                   type="playcollectRequestType"/>
                 <xs:element name="playrecord"
                   type="playrecordRequestType"/>



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                 <xs:element name="managecontent"
                   type="managecontentRequestType"/>
                 <xs:element name="faxplay"
                   type="faxRequestType"/>
                 <xs:element name="faxrecord"
                   type="faxRequestType"/>
                 <xs:element name="stop" type="stopRequestType"/>
               </xs:choice>
             </xs:complexType>
           </xs:element>
           <xs:element name="response" type="responseType"/>
           <xs:element name="notification">
             <xs:complexType>
               <xs:choice>
                 <xs:element name="conference"
                   type="conferenceNotificationType"/>
                 <xs:element name="keypress"
                   type="keypressNotificationType"/>
                 <xs:element name="signal"
                   type="signalNotificationType"/>
               </xs:choice>
             </xs:complexType>
           </xs:element>
         </xs:choice>
         <xs:attribute name="version" use="required"/>
       </xs:complexType>
     </xs:element>
     <!-- Definitions for base and concrete MSCML requests -->
     <!-- and embedded types. -->
     <xs:complexType name="base_requestType" abstract="true">
       <xs:attribute name="id" type="xs:string"/>
     </xs:complexType>
     <xs:complexType name="playRequestType">
       <xs:complexContent>
         <xs:extension base="base_requestType">
           <xs:sequence>
             <xs:element name="prompt" type="promptType"
               minOccurs="0"/>
           </xs:sequence>
           <xs:attribute name="prompturl" type="xs:string"/>
           <xs:attribute name="offset" type="xs:string"/>
           <xs:attribute name="promptencoding" type="xs:string"/>
         </xs:extension>
       </xs:complexContent>
     </xs:complexType>
     <xs:complexType name="configure_conferenceRequestType">
       <xs:complexContent>
         <xs:extension base="base_requestType">



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           <xs:sequence>
             <xs:element name="subscribe"
               type="conference_eventsubscriptionType" minOccurs="0"/>
           </xs:sequence>
           <xs:attribute name="reservedtalkers"
             type="xs:positiveInteger"/>
           <xs:attribute name="reserveconfmedia" type="yesnoType"
             default="yes"/>
         </xs:extension>
       </xs:complexContent>
     </xs:complexType>
     <xs:complexType name="configure_legRequestType">
       <xs:complexContent>
         <xs:extension base="base_requestType">
           <xs:sequence>
             <xs:element name="inputgain" type="gainType"
               minOccurs="0"/>
             <xs:element name="outputgain" type="gainType"
               minOccurs="0"/>
             <xs:element name="configure_team"
               type="configure_teamType" minOccurs="0"/>
             <xs:element name="subscribe"
               type="leg_eventsubscriptionType" minOccurs="0"/>
           </xs:sequence>
           <xs:attribute name="type">
             <xs:simpleType>
               <xs:restriction base="xs:NMTOKEN">
                 <xs:enumeration value="talker"/>
                 <xs:enumeration value="listener"/>
               </xs:restriction>
             </xs:simpleType>
           </xs:attribute>
           <xs:attribute name="mixmode">
             <xs:simpleType>
               <xs:restriction base="xs:NMTOKEN">
                 <xs:enumeration value="full"/>
                 <xs:enumeration value="mute"/>
                 <xs:enumeration value="preferred"/>
                 <xs:enumeration value="parked"/>
                 <xs:enumeration value="private"/>
               </xs:restriction>
             </xs:simpleType>
           </xs:attribute>
           <xs:attribute name="dtmfclamp" type="yesnoType"/>
           <xs:attribute name="toneclamp" type="yesnoType"/>
         </xs:extension>
       </xs:complexContent>
     </xs:complexType>



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     <xs:complexType name="configure_teamType">
       <xs:sequence>
         <xs:element name="teammate" type="teammateType" minOccurs="0"
           maxOccurs="unbounded"/>
       </xs:sequence>
       <xs:attribute name="id" type="xs:string"/>
       <xs:attribute name="action" use="required">
         <xs:simpleType>
           <xs:restriction base="xs:string">
             <xs:enumeration value="add"/>
             <xs:enumeration value="delete"/>
             <xs:enumeration value="query"/>
             <xs:enumeration value="set"/>
           </xs:restriction>
         </xs:simpleType>
       </xs:attribute>
     </xs:complexType>
     <xs:complexType name="teammateType">
       <xs:attribute name="id" type="xs:string" use="required"/>
     </xs:complexType>
     <xs:complexType name="playcollectRequestType">
       <xs:complexContent>
         <xs:extension base="base_requestType">
           <xs:sequence>
             <xs:element name="prompt" type="promptType"
               minOccurs="0"/>
             <xs:element name="pattern" type="dtmfGrammarType"
               minOccurs="0"/>
           </xs:sequence>
           <xs:attribute name="prompturl" type="xs:string"/>
           <xs:attribute name="offset" type="xs:string"/>
           <xs:attribute name="barge" type="yesnoType" default="yes"/>
           <xs:attribute name="promptencoding" type="xs:string"/>
           <xs:attribute name="cleardigits" type="yesnoType"
             default="no"/>
           <xs:attribute name="maxdigits" type="xs:string"/>
           <xs:attribute name="firstdigittimer" type="xs:string"
             default="5000ms"/>
           <xs:attribute name="interdigittimer" type="xs:string"
             default="2000ms"/>
           <xs:attribute name="extradigittimer" type="xs:string"
             default="1000ms"/>
           <xs:attribute name="interdigitcriticaltimer"
             type="xs:string"/>
           <xs:attribute name="skipinterval" type="xs:string"
             default="6s"/>
           <xs:attribute name="ffkey" type="DTMFkeyType"/>
           <xs:attribute name="rwkey" type="DTMFkeyType"/>



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           <xs:attribute name="returnkey" type="DTMFkeyType"
             default="#"/>
           <xs:attribute name="escapekey" type="DTMFkeyType"
             default="*"/>
           <xs:attribute name="maskdigits" type="yesnoType"
             default="no"/>
         </xs:extension>
       </xs:complexContent>
     </xs:complexType>
     <xs:complexType name="playrecordRequestType">
       <xs:complexContent>
         <xs:extension base="base_requestType">
           <xs:sequence>
             <xs:element name="prompt" type="promptType"
               minOccurs="0"/>
           </xs:sequence>
           <xs:attribute name="prompturl" type="xs:string"/>
           <xs:attribute name="promptencoding" type="xs:string"/>
           <xs:attribute name="offset" type="xs:string" default="0"/>
           <xs:attribute name="barge" type="yesnoType" default="yes"/>
           <xs:attribute name="cleardigits" type="yesnoType"
             default="no"/>
           <xs:attribute name="escapekey" type="xs:string" default="*"/>
           <xs:attribute name="recurl" type="xs:string" use="required"/>
           <xs:attribute name="mode" default="overwrite">
             <xs:simpleType>
               <xs:restriction base="xs:NMTOKEN">
                 <xs:enumeration value="append"/>
                 <xs:enumeration value="overwrite"/>
               </xs:restriction>
             </xs:simpleType>
           </xs:attribute>
           <xs:attribute name="recencoding" type="xs:string"/>
           <xs:attribute name="initsilence" type="xs:string"/>
           <xs:attribute name="endsilence" type="xs:string"/>
           <xs:attribute name="duration" type="xs:string"/>
           <xs:attribute name="beep" type="yesnoType" default="yes"/>
           <xs:attribute name="recstopmask" type="xs:string"
             default="01234567890*#"/>
         </xs:extension>
       </xs:complexContent>
     </xs:complexType>
     <xs:complexType name="managecontentRequestType">
       <xs:complexContent>
         <xs:extension base="base_requestType">
           <xs:attribute name="fetchtimeout" type="xs:string"
             default="10000"/>
           <xs:attribute name="mimetype" type="xs:string"/>



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           <xs:attribute name="name" type="xs:string"/>
           <xs:attribute name="httpmethod">
             <xs:simpleType>
               <xs:restriction base="xs:NMTOKEN">
                 <xs:enumeration value="put"/>
                 <xs:enumeration value="post"/>
               </xs:restriction>
             </xs:simpleType>
           </xs:attribute>
           <xs:attribute name="action">
             <xs:simpleType>
               <xs:restriction base="xs:NMTOKEN">
                 <xs:enumeration value="move"/>
                 <xs:enumeration value="delete"/>
               </xs:restriction>
             </xs:simpleType>
           </xs:attribute>
           <xs:attribute name="dest" type="xs:string"/>
           <xs:attribute name="src" type="xs:string" use="required"/>
         </xs:extension>
       </xs:complexContent>
     </xs:complexType>
     <xs:complexType name="stopRequestType">
       <xs:complexContent>
         <xs:extension base="base_requestType"/>
       </xs:complexContent>
     </xs:complexType>
     <xs:complexType name="faxRequestType">
       <xs:complexContent>
         <xs:extension base="base_requestType">
           <xs:sequence>
             <xs:element name="prompt" type="promptType" minOccurs="0"/>
           </xs:sequence>
           <xs:attribute name="lclid" type="xs:string"/>
           <xs:attribute name="prompturl" type="xs:string"/>
           <xs:attribute name="recurl" type="xs:string"/>
           <xs:attribute name="rmtid" type="xs:string"/>
         </xs:extension>
       </xs:complexContent>
     </xs:complexType>
     <xs:complexType name="dtmfGrammarType">
       <xs:choice>
         <xs:element name="regex" type="dtmfPatternType"
           maxOccurs="unbounded"/>
         <xs:element name="mgcpdigitmap" type="dtmfPatternType"/>
         <xs:element name="megacodigitmap" type="dtmfPatternType"/>
       </xs:choice>
     </xs:complexType>



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     <xs:complexType name="dtmfPatternType">
       <xs:attribute name="value" type="xs:string" use="required"/>
       <xs:attribute name="name" type="xs:string"/>
     </xs:complexType>
     <!-- Definitions for base and concrete MSCML responses -->
     <!-- and embedded types. -->
     <xs:complexType name="base_responseType" abstract="true">
       <xs:attribute name="request" use="required">
         <xs:simpleType>
           <xs:restriction base="xs:NMTOKEN">
             <xs:enumeration value="configure_conference"/>
             <xs:enumeration value="configure_leg"/>
             <xs:enumeration value="play"/>
             <xs:enumeration value="playcollect"/>
             <xs:enumeration value="playrecord"/>
             <xs:enumeration value="managecontent"/>
             <xs:enumeration value="faxplay"/>
             <xs:enumeration value="faxrecord"/>
             <xs:enumeration value="stop"/>
           </xs:restriction>
         </xs:simpleType>
       </xs:attribute>
       <xs:attribute name="id" type="xs:string"/>
       <xs:attribute name="code" type="xs:string" use="required"/>
       <xs:attribute name="text" type="xs:string" use="required"/>
     </xs:complexType>
     <xs:complexType name="responseType">
       <xs:complexContent>
         <xs:extension base="base_responseType">
           <xs:sequence>
             <xs:element name="error_info"
               type="stoponerrorResponseType" minOccurs="0"/>
             <xs:element name="team" type="configure_teamResponseType"
               minOccurs="0"/>
           </xs:sequence>
           <xs:attribute name="reason" type="xs:string"/>
           <xs:attribute name="reclength" type="xs:string"/>
           <xs:attribute name="recduration" type="xs:string"/>
           <xs:attribute name="digits" type="xs:string"/>
           <xs:attribute name="name" type="xs:string"/>
           <xs:attribute name="playduration" type="xs:string"/>
           <xs:attribute name="playoffset" type="xs:string"/>
           <xs:attribute name="faxcode" type="xs:string"/>
           <xs:attribute name="pages_sent" type="xs:string"/>
           <xs:attribute name="pages_recv" type="xs:string"/>
         </xs:extension>
       </xs:complexContent>
     </xs:complexType>



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     <xs:complexType name="stoponerrorResponseType">
       <xs:attribute name="code" type="xs:string" use="required"/>
       <xs:attribute name="text" type="xs:string" use="required"/>
       <xs:attribute name="context" type="xs:string" use="required"/>
     </xs:complexType>
     <xs:complexType name="configure_teamResponseType">
       <xs:sequence>
         <xs:element name="teammate" type="teammateType" minOccurs="0"
           maxOccurs="unbounded"/>
       </xs:sequence>
       <xs:attribute name="id" type="xs:string" use="required"/>
       <xs:attribute name="numteam" type="xs:integer" use="required"/>
     </xs:complexType>
     <!-- Definitions for MSCML event subscriptions and -->
     <!-- embedded types -->
     <xs:complexType name="conference_eventsubscriptionType">
       <xs:sequence>
         <xs:element name="events">
           <xs:complexType>
             <xs:sequence>
               <xs:element name="activetalkers"
                 type="activetalkersSubscriptionType"/>
             </xs:sequence>
           </xs:complexType>
         </xs:element>
       </xs:sequence>
     </xs:complexType>
     <xs:complexType name="activetalkersSubscriptionType">
       <xs:attribute name="report" type="yesnoType" use="required"/>
       <xs:attribute name="interval" type="xs:string" default="60s"/>
     </xs:complexType>
     <xs:complexType name="leg_eventsubscriptionType">
       <xs:sequence>
         <xs:element name="events">
           <xs:complexType>
             <xs:sequence>
               <xs:element name="keypress"
                 type="keypressSubscriptionType" minOccurs="0"
                   maxOccurs="1"/>
               <xs:element name="signal" type="signalSubscriptionType"
                 minOccurs="0" maxOccurs="unbounded"/>
             </xs:sequence>
           </xs:complexType>
         </xs:element>
       </xs:sequence>
     </xs:complexType>
     <xs:complexType name="keypressSubscriptionType">
       <xs:attribute name="report" use="required">



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         <xs:simpleType>
           <xs:restriction base="xs:NMTOKEN">
             <xs:enumeration value="standard"/>
             <xs:enumeration value="long"/>
             <xs:enumeration value="both"/>
             <xs:enumeration value="none"/>
           </xs:restriction>
         </xs:simpleType>
       </xs:attribute>
       <xs:attribute name="maskdigits" type="yesnoType" default="no"/>
     </xs:complexType>
     <xs:complexType name="signalSubscriptionType">
       <xs:attribute name="type" type="xs:NMTOKEN" use="required"/>
       <xs:attribute name="report" type="yesnoType" use="required"/>
     </xs:complexType>
     <!-- Definitions for MSCML event notifications and -->
     <!-- embedded types. -->
     <xs:complexType name="conferenceNotificationType">
       <xs:sequence>
         <xs:element name="activetalkers"
           type="activetalkersNotificationType" minOccurs="0"/>
       </xs:sequence>
       <xs:attribute name="uniqueid" type="xs:string" use="required"/>
       <xs:attribute name="numtalkers" type="xs:string"
         use="required"/>
     </xs:complexType>
     <xs:complexType name="activetalkersNotificationType">
       <xs:sequence minOccurs="0">
         <xs:element name="talker" maxOccurs="unbounded">
           <xs:complexType>
             <xs:attribute name="callid" type="xs:string"
              use="required"/>
           </xs:complexType>
         </xs:element>
       </xs:sequence>
     </xs:complexType>
     <xs:complexType name="keypressNotificationType">
       <xs:sequence>
         <xs:element name="status" type="statusType"/>
       </xs:sequence>
       <xs:attribute name="digit" type="DTMFkeyType" use="required"/>
       <xs:attribute name="length" use="required">
         <xs:simpleType>
           <xs:restriction base="xs:NMTOKEN">
             <xs:enumeration value="standard"/>
             <xs:enumeration value="long"/>
           </xs:restriction>
         </xs:simpleType>



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       </xs:attribute>
       <xs:attribute name="method" use="required">
         <xs:simpleType>
           <xs:restriction base="xs:NMTOKEN">
             <xs:enumeration value="standard"/>
             <xs:enumeration value="long"/>
             <xs:enumeration value="double"/>
           </xs:restriction>
         </xs:simpleType>
       </xs:attribute>
       <xs:attribute name="interdigittime" type="xs:string"
         use="required"/>
     </xs:complexType>
     <xs:complexType name="statusType">
       <xs:attribute name="command" use="required">
         <xs:simpleType>
           <xs:restriction base="xs:string">
             <xs:enumeration value="idle"/>
             <xs:enumeration value="play"/>
             <xs:enumeration value="collect"/>
             <xs:enumeration value="record"/>
           </xs:restriction>
         </xs:simpleType>
       </xs:attribute>
       <xs:attribute name="duration" type="xs:string" use="required"/>
     </xs:complexType>
     <xs:complexType name="signalNotificationType">
       <xs:attribute name="type" use="required" fixed="busy"/>
     </xs:complexType>
     <!-- Definitions for miscellaneous embedded, helper data types -->
     <xs:complexType name="promptType">
       <xs:choice maxOccurs="unbounded">
         <xs:element name="audio" type="promptcontentType"/>
         <xs:element name="variable" type="spokenvariableType"/>
       </xs:choice>
       <xs:attribute name="locale" type="xs:string"/>
       <xs:attribute name="baseurl" type="xs:string"/>
       <xs:attribute name="stoponerror" type="yesnoType" default="no"/>
       <xs:attribute name="gain" type="xs:string" default="0"/>
       <xs:attribute name="gaindelta" type="xs:string" default="0"/>
       <xs:attribute name="rate" type="xs:string" default="0"/>
       <xs:attribute name="ratedelta" type="xs:string" default="0"/>
       <xs:attribute name="repeat" type="xs:string" default="1"/>
       <xs:attribute name="duration" type="xs:string"
         default="infinite"/>
       <xs:attribute name="offset" type="xs:string" default="0"/>
       <xs:attribute name="delay" type="xs:string" default="0"/>
     </xs:complexType>



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     <xs:complexType name="promptcontentType">
       <xs:attribute name="url" type="xs:string" use="required"/>
       <xs:attribute name="encoding" type="xs:string"/>
       <xs:attribute name="gain" type="xs:string" default="0"/>
       <xs:attribute name="gaindelta" type="xs:string" default="0"/>
       <xs:attribute name="rate" type="xs:string" default="0"/>
       <xs:attribute name="ratedelta" type="xs:string" default="0"/>
     </xs:complexType>
     <xs:complexType name="spokenvariableType">
       <xs:attribute name="type" use="required">
         <xs:simpleType>
           <xs:restriction base="xs:NMTOKEN">
             <xs:enumeration value="dat"/>
             <xs:enumeration value="dig"/>
             <xs:enumeration value="dur"/>
             <xs:enumeration value="mth"/>
             <xs:enumeration value="mny"/>
             <xs:enumeration value="num"/>
             <xs:enumeration value="sil"/>
             <xs:enumeration value="str"/>
             <xs:enumeration value="tme"/>
             <xs:enumeration value="wkd"/>
           </xs:restriction>
         </xs:simpleType>
       </xs:attribute>
       <xs:attribute name="subtype">
         <xs:simpleType>
           <xs:restriction base="xs:NMTOKEN">
             <xs:enumeration value="mdy"/>
             <xs:enumeration value="dmy"/>
             <xs:enumeration value="ymd"/>
             <xs:enumeration value="ndn"/>
             <xs:enumeration value="t12"/>
             <xs:enumeration value="t24"/>
             <xs:enumeration value="USD"/>
             <xs:enumeration value="gen"/>
             <xs:enumeration value="ndn"/>
             <xs:enumeration value="crd"/>
             <xs:enumeration value="ord"/>
           </xs:restriction>
         </xs:simpleType>
       </xs:attribute>
       <xs:attribute name="value" type="xs:string" use="required"/>
     </xs:complexType>
     <xs:simpleType name="yesnoType">
       <xs:restriction base="xs:NMTOKEN">
         <xs:enumeration value="yes"/>
         <xs:enumeration value="no"/>



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         <xs:enumeration value="1"/>
         <xs:enumeration value="0"/>
         <xs:enumeration value="true"/>
         <xs:enumeration value="false"/>
       </xs:restriction>
     </xs:simpleType>
     <xs:simpleType name="DTMFkeyType">
       <xs:restriction base="xs:string">
         <xs:pattern value="[0-9]"/>
         <xs:pattern value="[A-D]"/>
         <xs:pattern value="[a-d]"/>
         <xs:pattern value="#"/>
         <xs:pattern value="\*"/>
       </xs:restriction>
     </xs:simpleType>
     <xs:complexType name="gainType">
       <xs:choice>
         <xs:element name="auto" type="autogainType"/>
         <xs:element name="fixed" type="fixedgainType"/>
       </xs:choice>
     </xs:complexType>
     <xs:complexType name="autogainType">
       <xs:attribute name="startlevel" type="xs:string"/>
       <xs:attribute name="targetlevel" type="xs:string"/>
       <xs:attribute name="silencethreshold" type="xs:string"/>
     </xs:complexType>
     <xs:complexType name="fixedgainType">
       <xs:attribute name="level" type="xs:string"/>
     </xs:complexType>
   </xs:schema>

12.  IANA Considerations

12.1.  IANA Registration of MIME Media Type application/
      mediaservercontrol+xml

      MIME media type name: application
      MIME subtype name: mediaservercontrol+xml
      Required parameters: none
      Optional parameters: charset

      charset This parameter has identical semantics to the charset
         parameter of the "application/xml" media type, as specified in
         XML Media Types [8].

   Encoding considerations: See RFC 3023 [8].
   Interoperability considerations: See RFC 2023 [8] and RFC 5022.
   Published specification: RFC 5022



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   Applications that use this media type: Multimedia, enhanced
      conferencing and interactive applications.
   Personal and email address for further
      information: eburger@cantata.com [31]
   Intended usage: COMMON

13.  Security Considerations

   Because media flows through a media server in a conference, the media
   server itself MUST protect the integrity, confidentiality, and
   security of the sessions.  It should not be possible for a conference
   participant, on her own behalf, to be able to "tap in" to another
   conference without proper authorization.

   Because conferencing is a high-value application, the media server
   SHOULD implement appropriate security measures.  This includes, but
   is not limited to, access lists for application servers.  That is,
   the media server only allows a select list of application or proxy
   servers to create conferences, to invite participants to sessions,
   etc.  Note that the mechanisms for such security, like private
   networks, shared certificates, MAC white/black lists, are beyond the
   scope of this document.

   Security concerns are one important reason MSCML limits requests with
   conference scope to a separate control leg per conference.  MSCML
   uses the simple, proven, Internet-scale security model of SIP to
   determine if a client is who they say they are (authentication) and
   if they are allowed to create and manipulate a conference.  However,
   the security model to enable a control leg to manipulate arbitrary
   conferences on the media server is extremely difficult.  Not only
   would one need to authenticate and authorize the basic conference
   primitives, but privacy considerations require policies for one
   client to access another client's conferences, even if the two
   clients are on the same host.  For example, if the media server
   allowed any control leg to control any conference, an authorized but
   unrelated client could maliciously attach itself to an existing
   session and record or tap the conversation without the participant's
   knowledge or consent.

   Participants give implicit authorization to their applications by
   virtue of the INVITE to the application.  However, there is no trust,
   explicit or implicit, between the users of one service and a distinct
   client of another service.

   All MSCML messages are sent within an INVITE-created SIP dialog.  As
   a result, it would be difficult for an entity other than the original
   requestor to interfere with an established MSCML session, as this
   would require detailed information on the dialog state.  This allows



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   multiple applications to utilize the resources of a single media
   server simultaneously without interfering with one another.

   Because of the sensitive nature of collected data, such as credit
   card numbers or other identifying information, the media server MUST
   support sips: and TLS.  Clients, who presumably know the value of the
   information they collect, as well as the privacy expectations of
   their users, are free to use clear text signaling or encrypted secure
   signaling, depending on the application's needs.  Likewise, the media
   server SHOULD support Secure Realtime Transport Protocol (SRTP) [9].
   Again, the clients are free to negotiate the appropriate level of
   media security.

   The media management facilities of MSCML, such as the <managecontent>
   (Section 8) request, assume a trust relationship between the media
   server and file server.  This scenario is similar to the one
   addressed by URLAUTH [20].  Namely, the media server is acting on
   behalf of a given user, yet the media server does not have
   credentials for that user.  One might be tempted to use the user:pass
   facility of the HTTP URI to offer per-user security, but that also
   requires that the media server be secure, as the media server would
   need to know the user credentials in a form that is easily
   compromised (clear text passwords).

   The IETF is investigating methods for providing per-user or per-
   instance authorization of third-party http writing, as is needed for
   other protocols as well, such as WEBDAV [21].  However, until that
   work is completed, media server implementations MUST be prepared to
   authenticate themselves to file and web servers using appropriate
   authentication means.  At a minimum, the media server MUST support
   HTTPS basic authentication.  Implementers should note that the media
   server will need to respond appropriately to whatever authentication
   mechanism the file server requires.

   As this is an XML markup, all the security considerations of RFC 3023
   [8] apply.

14.  References

14.1.  Normative References

   [1]   Bradner, S., "Key words for use in RFCs to Indicate Requirement
         Levels", BCP 14, RFC 2119, March 1997.

   [2]   Burger, E., Van Dyke, J., and A. Spitzer, "Basic Network Media
         Services with SIP", RFC 4240, December 2005.

   [3]   Donovan, S., "The SIP INFO Method", RFC 2976, October 2000.



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   [4]   Rosenberg, J., Schulzrinne, H., Camarillo, G., Johnston, A.,
         Peterson, J., Sparks, R., Handley, M., and E. Schooler, "SIP:
         Session Initiation Protocol", RFC 3261, June 2002.

   [5]   "Network call signalling protocol for the delivery of time-
         critical services over cable television networks using cable
         modems", ITU-T J.162, March 2001.

   [6]   Groves, C., Pantaleo, M., Anderson, T., and T. Taylor, "Gateway
         Control Protocol Version 1", RFC 3525, June 2003.

   [7]   Thompson, H., Beech, D., Maloney, M., and N. Mendelsohn, "XML
         Schema Part 1: Structures", W3C REC REC-xmlschema-1-20010502,
         May 2001.

   [8]   Murata, M., St. Laurent, S., and D. Kohn, "XML Media Types",
         RFC 3023, January 2001.

   [9]   Baugher, M., McGrew, D., Naslund, M., Carrara, E., and K.
         Norrman, "The Secure Real-time Transport Protocol (SRTP)", RFC
         3711, March 2004.

14.2.  Informative References

   [10]  Rosenberg, J., "A Framework for Conferencing with the Session
         Initiation Protocol (SIP)", RFC 4353, February 2006.

   [11]  Carter, J., Danielsen, P., Hunt, A., Ferrans, J., Lucas, B.,
         Porter, B., Rehor, K., Tryphonas, S., McGlashan, S., and D.
         Burnett, "Voice Extensible Markup Language (VoiceXML) Version
         2.0", W3C REC REC-voicexml20-20040316, March 2004.

   [12]  International Packet Communications Consortium, "IPCC Reference
         Architecture V2", June 2002.

   [13]  European Telecommunications Standards Institute, "Digital
         cellular telecommunications system (Phase 2+); Universal Mobile
         Telecommunications System (UMTS); IP Multimedia Subsystem
         (IMS); Stage 2 (3GPP TS 23.228 version 7.2.0 Release 7)",
         December 2005.

   [14]  Hollenbeck, S., Rose, M., and L. Masinter, "Guidelines for the
         Use of Extensible Markup Language (XML) within IETF Protocols",
         BCP 70, RFC 3470, January 2003.

   [15]  Jacobs, I., Lie, H., Bos, B., and C. Lilley, "Cascading Style
         Sheets, level 2 (CSS2) Specification", W3C REC REC-CSS2-
         19980512, May 1998.



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   [16]  Rosenberg, J., Schulzrinne, H., and O. Levin, "A Session
         Initiation Protocol (SIP) Event Package for Conference State",
         RFC 4575, August 2006.

   [17]  Cable Television Laboratories, Inc., "Audio Server Protocol",
         January 2005.

   [18]  "Procedures for document facsimile transmission in the general
         switched telephone network", Recommendation T.30, April 1999.

   [19]  "Procedures for real-time Group 3 facsimile communication over
         IP networks", Recommendation T.38, March 2002.

   [20]  Crispin, M., "Internet Message Access Protocol (IMAP) - URLAUTH
         Extension", RFC 4467, May 2006.

   [21]  Dusseault, L., Ed., "HTTP Extensions for Web Distributed
         Authoring and Versioning (WebDAV)", RFC 4918, June 2007.

   [22]  Institute of Electrical and Electronics Engineers, "Information
         Technology - Portable Operating System Interface (POSIX) - Part
         1: Base Definitions, Chapter 9", IEEE Standard 1003.1, June
         2001.

   [23]  Burger, E. and M. Dolly, "A Session Initiation Protocol (SIP)
         Event Package for Key Press Stimulus (KPML)", RFC 4730,
         November 2006.

   [24]  Klensin, J., "Simple Mail Transfer Protocol", RFC 2821, April
         2001.

   [25]  Campbell, B., Ed., Mahy, R., Ed., and C. Jennings, Ed., "The
         Message Session Relay Protocol", Work in Progress, February
         2007.

URIs

   [26]  <http://www.ietf.org/html.charters/sip-charter.html>

   [27]  <http://www.ietf.org/html.charters/sipping-charter.html>

   [28]  <http://www.ietf.org/html.charters/mmusic.html>

   [29]  <http://www.ietf.org/html.charters/xcon-charter.html>

   [30]  <http://www.3gpp.org/ftp/Specs/html-info/23228.htm>

   [31]  <mailto:eburger@cantata.com>



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Appendix A.  Regex Grammar Syntax

   The regular expression syntax used in MSCML is a telephony-oriented
   subset of POSIX Extended Regular Expressions (ERE) [22] termed Digit
   REGular EXpression (DRegex).  This syntax was first described in KPML
   [23].

   DRegex includes ordinary characters, special characters, bracket
   expressions, and interval expressions.  These entities are defined in
   the list below.

   . matches digits 0-9, *, #, and A-D (case insensitive)
   *  matches the * character
   #  matches the # character
   [character selector] matches any character in selector
   [range1-range2] matches any character in range from range1 to range2,
      inclusive
   x  matches any digit 0-9
   {m} matches m repetitions of the previous pattern
   {m,} matches m or more repetitions of the previous pattern
   {,n} matches at most n (including zero) repetitions of the previous
      pattern
   {m,n} at least m and at most n repetitions of the previous pattern
   L  the presence of 'L' in any regex expression causes the media
      server to enable "long" digit detection mode.  See Section 7.1 for
      the definition of "long" digits.

   Table 7 illustrates DRegex usage through examples.

       +--------------+--------------------------------------------+
       | Example      | Description                                |
       +--------------+--------------------------------------------+
       | 1            | Matches the digit 1                        |
       | [179]        | Matches 1, 7, or 9                         |
       | [2-9]        | Matches 2, 3, 4, 5, 6, 7, 8, 9             |
       | [02-46-9A-D] | Matches 0, 2, 3, 4, 6, 7, 8, 9, A, B, C, D |
       | x            | Matches 0, 1, 2, 3, 4, 5, 6, 7, 8, 9       |
       | .            | Matches 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, A, B,|
       |              | C, D, #, *                                 |
       | *6[179#]     | Matches *61, *67, *69, or *6#              |
       | x{10}        | Ten digits (0-9)                           |
       | 011x{7,15}   | 011 followed by seven to fifteen digits    |
       | L*           | Long star                                  |
       +--------------+--------------------------------------------+

                         Table 7: DRegex Examples





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Appendix B.  Contributors

   Jeff Van Dyke and Andy Spitzer did the concept, development,
   documentation, and execution for MSCML at SnowShore Networks, Inc.,
   which is now part of Cantata Technology, Inc.  Andy Spitzer's
   original work at The Telephone Connection, Inc., influenced the IVR
   implementation.  Mary Ann Leekley implemented the personalized mix
   feature and several other enhancements.

   Cliff Schornak of Commetrex and Jeff Van Dyke developed the facsimile
   service.

   Jai Cauvet, Rolando Herrero, Srinivas Motamarri, and Ashish Patel
   contributed greatly by testing MSCML.

Appendix C.  Acknowledgements

   The following individuals provided valuable assistance in the
   direction, development, or debugging of MSCML:

   o  Brian Badger and Phil Crable from Verizon Business
   o  Stephane Bastien from BroadSoft
   o  Peter Danielsen of Lucent Technologies
   o  Kevin Flemming, formerly of SnowShore Networks, Inc.
   o  Wesley Hicks and Ravindra Kabre, formerly from Sonus Networks
   o  Jon Hinckley from SkyWave/Sestro
   o  Terence Lobo, formerly of SnowShore Networks, Inc.
   o  Kunal Nawale, formerly of SnowShore Networks, Inc.
   o  Edwina Nowicki, formerly of SnowShore Networks, Inc.
   o  Diana Rawlins and Sharadha Vijay, formerly of WorldCom
   o  Gaurav Srivastva and Subhash Verma from BayPackets
   o  Kevin Summers from Sonus Networks
   o  Tim Wong from at&t

   The authors would like to thank Cullen Jennings and Dan Wing from
   Cisco Systems for their helpful review comments.

   The authors would also like to thank Scotty Farber for applying her
   technical writing expertise to the documentation of MSCML.












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Authors' Addresses

   Jeff Van Dyke
   Cantata Technology, Inc.
   18 Keewaydin Dr.
   Salem, NH  03079
   USA

   EMail: jvandyke@cantata.com


   Eric Burger (editor)
   BEA Systems, Inc.
   USA

   Email: eburger@standardstrack.com
   URI: http://www.standardstrack.com


   Andy Spitzer
   Bluesocket Inc.
   10 North Avenue
   Burlington, MA  01803
   USA

   EMail: woof@pingtel.com

























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Full Copyright Statement

   Copyright (C) The IETF Trust (2007).

   This document is subject to the rights, licenses and restrictions
   contained in BCP 78 and at www.rfc-editor.org/copyright.html, and
   except as set forth therein, the authors retain all their rights.

   This document and the information contained herein are provided on an
   "AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE REPRESENTS
   OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY, THE IETF TRUST,
   AND THE INTERNET ENGINEERING TASK FORCE DISCLAIM ALL WARRANTIES,
   EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT
   THE USE OF THE INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY
   IMPLIED WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR
   PURPOSE.

Intellectual Property

   The IETF takes no position regarding the validity or scope of any
   Intellectual Property Rights or other rights that might be claimed to
   pertain to the implementation or use of the technology described in
   this document or the extent to which any license under such rights
   might or might not be available; nor does it represent that it has
   made any independent effort to identify any such rights.  Information
   on the procedures with respect to rights in RFC documents can be
   found in BCP 78 and BCP 79.

   Copies of IPR disclosures made to the IETF Secretariat and any
   assurances of licenses to be made available, or the result of an
   attempt made to obtain a general license or permission for the use of
   such proprietary rights by implementers or users of this
   specification can be obtained from the IETF on-line IPR repository at
   http://www.ietf.org/ipr.

   The IETF invites any interested party to bring to its attention any
   copyrights, patents or patent applications, or other proprietary
   rights that may cover technology that may be required to implement
   this standard.  Please address the information to the IETF at
   ietf-ipr@ietf.org.











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