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+Network Working Group                                        L. Masinter
+Request for Comments: 2542                             Xerox Corporation
+Category: Informational                                       March 1999
+
+
+                 Terminology and Goals for Internet Fax
+
+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.
+
+Copyright Notice
+
+   Copyright (C) The Internet Society (1999).  All Rights Reserved.
+
+Abstract
+
+   This document defines a number of terms useful for the discussion of
+   Internet Fax. In addition, it describes the goals of the Internet Fax
+   working group and establishes a baseline of desired functionality
+   against which protocols for Internet Fax can be judged. It
+   encompasses the goals for all modes of facsimile delivery, including
+   'real-time', 'session', and 'store and forward'.  Different levels of
+   desirability are indicated throughout the document.
+
+Table of Contents
+
+   1. Introduction ..................................................  2
+   2. Definitions and Operational Modes .............................  3
+    2.1 User model of fax ...........................................  3
+    2.2 Definition of Internet Fax ..................................  4
+    2.3 Internet Fax Roles ..........................................  5
+    2.4 Internet Fax Devices ........................................  5
+    2.5 Operational modes ...........................................  8
+   3. Goals for Internet Fax ........................................  8
+   4. Operational Goals for Internet Fax ............................  9
+    4.1 Functionality ...............................................  9
+    4.2 Interoperability ............................................  9
+    4.3 Confirmation ................................................ 10
+    4.4 Quick Delivery .............................................. 11
+    4.5 Capabilities ................................................ 12
+    4.6 Simplicity .................................................. 12
+    4.7 Security .................................................... 13
+    4.8 Reliability ................................................. 14
+    4.9 Fax-like use ................................................ 14
+    4.10 Legal ...................................................... 15
+
+
+
+Masinter                     Informational                      [Page 1]
+
+RFC 2542         Terminology and Goals for Internet Fax       March 1999
+
+
+   5. Functional Goals for Internet Fax ............................. 15
+    5.1 Goals for image data representation ......................... 15
+    5.2 Goals for transmission ...................................... 16
+    5.3 Goals for addressing ........................................ 16
+    5.4 Goals for security .......................................... 17
+    5.5 Goals for capability exchange ............................... 17
+   6. Security Considerations ....................................... 18
+   7. Acknowledgements .............................................. 18
+   8. Author's Address .............................................. 18
+   9. References .................................................... 19
+   10. Full Copyright Statement ..................................... 20
+
+1. Introduction
+
+   Facsimile (Fax) has a long tradition as a telephony application for
+   sending a document from one terminal device to another.
+
+   Many mechanisms for sending fax documents over the Internet have been
+   demonstrated and deployed and are currently in use. The general
+   application of using the Internet for facsimile is called "Internet
+   Fax".
+
+   This document defines a number of terms useful for the discussion of
+   Internet Fax. In addition, it describes the goals for Internet Fax and
+   establishes a baseline of desired functionality against which
+   protocols for Internet Fax can be judged. It encompasses the goals for
+   all modes of facsimile delivery, including "real-time", "session", and
+   "store and forward" (terms defined in Section 2 of this document).
+
+   1.1 Terminology used within this document
+
+   Within this document, different levels of desirability for a protocol
+   for Internet Fax are indicated by different priorities, indicated in
+   {braces}:
+
+      {1} there is general agreement that this is a critical
+          characteristic of any definition of Internet Fax.
+      {2} most believe that this is an important characteristic
+          of Internet Fax.
+      {3} there is general belief that this is a useful feature
+          of Internet Fax, but that other factors might override;
+          a definition that does not provide this element is
+          acceptable.
+
+
+
+
+
+
+
+
+Masinter                     Informational                      [Page 2]
+
+RFC 2542         Terminology and Goals for Internet Fax       March 1999
+
+
+   In addition, the following terms are used:
+
+   "service"      An operational service offered by a service provider.
+   "application"  A use of systems to perform a particular function.
+   "terminal"     The endpoint of a communication application.
+   "goal"         An objective of the standarization process.
+
+2. Definitions and Operation Modes
+
+   This section defines some of the basic terms for Internet Fax.
+
+2.1 User model of fax and basic operations
+
+   The phrase "traditional facsimile" or "G3Fax" is used to denote
+   implementations of [T.30]. Facsimile (fax) is a telephony application
+   for sending a document from one terminal device to another.
+
+   The telephone network is often referred to as the Public Switched
+   Telephone Network (PSTN) or Global Switched Telephone Network (GSTN).
+
+   Communication over the telephone network is accomplished using
+   modems.  The transmission of data end-to-end is accompanied by
+   negotiation (to ensure that the scanned data can be rendered at the
+   recipient) and confirmation of delivery (to give the sender assurance
+   that the final data has been received and processed.)  Over time,
+   facsimile has been extended to allow for PCs using fax modems to send
+   and receive fax, to send data other than scanned facsimile images. In
+   addition, there have been many extensions to the basic image model,
+   to allow for additional compression methods and for representation of
+   images with grey-scale and color. Other delivery extensions have
+   included sub-addressing (additional signals after the call is
+   established to facilitate automated routing of faxes to desktops or
+   mailboxes), and enhanced features such as fax-back and polling.
+
+   Typically, the terminal device consists of a paper input device
+   (scanner), a paper output device (printer), with (a limited amount
+   of) processing power. Traditional facsimile has a simple user
+   operational model; the user
+
+      1) inserts paper into a device
+      2) dials a number corresponding to the destination
+      3) presses the 'start' button on the device
+      4) the sending device connects to the receiving device using the
+         telephone network
+      5) the sending device scans the paper and transmits the image of
+         the paper
+      6) simultaneously, the remote device receives the transmission and
+         prints the image on paper
+
+
+
+Masinter                     Informational                      [Page 3]
+
+RFC 2542         Terminology and Goals for Internet Fax       March 1999
+
+
+      7) upon completion of transmission and successful processing by
+         the recipient, the sending user is notified of success
+
+   Although not usually visible to the user, the operation (5) of
+   transmission consists of
+
+      5a) negotiation: the capabilities of the recipient are obtained,
+          and suitable mutually available parameters for the
+          communication are selected
+      5b) scanning: creating digitized images of pages of a document
+      5c) compression: the image data is encoded using a data
+          compression method
+      5d) transmission: the data is sent from one terminal to the other
+
+   In addition, the terminiation of operations (5d) and (6) may be
+   characterized as consisting of:
+
+      6a) completed delivery: the message has completed transmission
+      6b) completed receipt:  the message has been accepted by the
+          recipient
+      6c) processing and disposition: the message has been processed
+
+   From a protocol perspective, the information conveyed in the
+   transmission consists of both "protocol" (control information,
+   capabilities, identification) and also "document content".
+
+   The document content consists primarily of the "document image" plus
+   additional metadata accompanying the image. The means by which an
+   image of a document is encoded within the fax content is the "image
+   data representation".
+
+   When the fax has been successfully transmitted, the sender receives a
+   "confirmation": an indication that the fax content was delivered.
+   This "confirmation" is an internal signal and is not normally visible
+   to the sending user, although some error messages are visible, to
+   allow a page to be retransmitted.
+
+2.2 Definition of Internet Fax
+
+   The phrase "Internet Fax" is used to denote an application which
+   supports an approximation to the user model of fax (Section 2.1), but
+   where Internet protocols are used instead of the telephone network
+   for (some portion of) the transmission. The exact modes and
+   operations of traditional facsimile need not be duplicated exactly.
+
+
+
+
+
+
+
+Masinter                     Informational                      [Page 4]
+
+RFC 2542         Terminology and Goals for Internet Fax       March 1999
+
+
+2.3 Internet Fax Roles
+
+   Internet Fax is a document transmission mechanism between various
+   different devices and roles. Those devices and roles might come in a
+   wide variety of configurations. To allow for a wide variety of
+   configurations, it is useful to separate out the roles, as they may
+   be made available separately or in combination. These roles are:
+
+      * Network scanner
+        A device that can scan a paper document and transmit the scanned
+        image via the Internet
+
+      * Network printer
+        A device that can accept an image transmission via the Internet
+        and print the received document automatically
+
+      * Fax onramp gateway
+        A device that can accept a facsimile telephone call and
+        automatically forward it via the Internet
+
+      * Fax offramp gateway
+        A device that can accept a transmission from the Internet and
+        forward it to a traditional fax terminal
+
+   In addition, other traditional Internet applications might also
+   participate in Internet Fax, including Internet mail users, Web
+   browsers, Internet printing hosts.
+
+2.4 Internet Fax Devices
+
+   The Internet Fax roles may be embedded in a variety of combinations
+   and configurations within devices and larger applications.  They may
+   be combined with other elements, e.g., a traditional T.30 fax device.
+   Many different configurations of applications and systems should {2}
+   be able to participate in Internet Fax; the specification should not
+   unnecessarily restrict the range of devices, applications and
+   services that can participate.
+
+   A device that supports Internet Fax might support any combination of
+   the roles defined in 2.3.
+
+2.4.1 Gateway devices
+
+   A traditional fax terminal has a telephone line connection (GSTN)
+   with a fax modem used to connect over the telephone network. To
+   connect a fax terminal to the Internet requires a service which
+   offers connections on one side to the GSTN using standard fax
+   signals, and on the other side to the Internet. This role might be
+
+
+
+Masinter                     Informational                      [Page 5]
+
+RFC 2542         Terminology and Goals for Internet Fax       March 1999
+
+
+   performed by a "relay" (e.g., transmitting T.30 signals over real-
+   time controlled TCP connections) or a "gateway" (e.g., translating
+   T.30 to TIFF/email).
+
+   With these applications, the role of Internet Fax is to transport the
+   fax content across the Internet, e.g., with
+
+[fax-term]-GSTNfax->[onramp]-Internet Fax->[recipient]
+                    [sender]-Internet Fax->[offramp]-GSTNFax->[fax-term]
+
+   A onramp and/or offramp application may be local to a single fax
+   terminal.  For example, the gateway application might exist within a
+   small device which has a telephone interface on one side and a
+   network connection on the other. To the fax machine, it looks like a
+   telephone connection, although it might shunt some or all connections
+   to Internet Fax instead (Such devices are called "Bump-in-cord.")
+
+   An onramp or offramp application may be a local facility serving many
+   fax terminals. For example, outgoing telephone fax calls through a
+   company telephone PBX could be rerouted through a local onramp. An
+   internet to telephone outbound connection could be part of a "LAN
+   Fax" package.
+
+   Onramps and offramps may serve a wider area or broader collection of
+   users, e.g., services run by service bureaus, offering subscription
+   services; the telephone sender or the recipient might subscribe to
+   the service.
+
+   The target of an offramp may be a "hunt group": a set of telephone
+   numbers, each of which have a possibly different fax terminal
+   attached.
+
+2.4.2 New "Internet Fax" devices
+
+   Manufacturers may offer new devices which support any combination of
+   the roles defined in setion 2.3. In particular, a device resembling a
+   traditional fax terminal, built out of similar components (scanner,
+   processor, and printer), could offer a similar functionality to a
+   traditional facsimile terminal, but be designed to connect to the
+   Internet rather than, or in addition to, a telephone line connection.
+
+   Such devices might have a permanent Internet connection (through a
+   LAN connection) or might have occasional connectivity through a
+   (data) modem to an Internet Service Provider.
+
+
+
+
+
+
+
+Masinter                     Informational                      [Page 6]
+
+RFC 2542         Terminology and Goals for Internet Fax       March 1999
+
+
+2.4.3 Internet hosts
+
+   Internet users using Internet hosts with standard application suites
+   must {1} be able to exchange faxes with other participants in
+   Internet Fax, with minimum required enhancements to their operating
+   environment.
+
+   Interoperability with Internet mail users, either as Internet Fax
+   senders or recipients, is highly desirable {2}.
+
+   Internet users might receive faxes over the Internet and display them
+   on their screens, or have them automatically printed when received.
+   Similarly, the Internet Fax messages originating from the user might
+   be the output of a software application which would normally print,
+   or specially constructed fax-sending software, or may be input
+   directly from a scanner attached to the user's terminal.
+
+   The Internet Fax capability might be integrated into existing
+   fax/network fax software or email software, e.g., by the addition of
+   printer drivers that would render the document to the appropriate
+   content-type and cause it to be delivered using an Internet Fax
+   protocol.
+
+   In some cases, the user might have a multi-function peripheral which
+   integrated a scanner and printer and which gave operability similar
+   to that of the stand-alone fax terminal.
+
+2.4.4 Internet messaging
+
+   In Internet mail, there are a number of components that operate in
+   the infrastructure to perform additional functions beyond mail
+   store-and-forward. Interoperability with these components is a
+   consideration for the store and forward profile of Internet Fax.  For
+   example, mailing list software accepts mail to a single address and
+   forwards it to a distribution list of many users. Mail archive
+   software creates repositories of searchable messages. Mail firewalls
+   operate at organizational boundaries and scan incoming messages for
+   malicious or harmful mail attachments. Vacation programs send return
+   messages to the senders of messages when the recipient is on vacation
+   and not available to respond.
+
+2.4.5 Universal messaging
+
+   Many software vendors are now promoting software packages that
+   support "universal messaging": a combined communication package that
+   combines electronic mail, voice mail, and fax.
+
+
+
+
+
+Masinter                     Informational                      [Page 7]
+
+RFC 2542         Terminology and Goals for Internet Fax       March 1999
+
+
+2.5 Operational Modes for Internet Fax
+
+   Facsimile over the Internet can occur in several modes.
+
+   "Store and forward" Internet Fax entails a process of storing the
+   entire document at a staging point, prior to transmitting it to the
+   next staging point. Store and forward can be directly between sender
+   and recipient or can have a series of intermediary staging points.
+   The intermediate storage may involve an intermediate agent or
+   sequence of agents in the communication.
+
+   "Session" Internet Fax is defined such that delivery notification is
+   provided to the transmitting terminal prior to disconnection. Unlike
+   "store and forward", there is an expection that direct communication,
+   negotiation, and retransmission can take place between the two
+   endpoints.
+
+   "Real-time" Internet Fax allows for two [T.30] standard facsimile
+   terminals to engage in a document transmission in a way that all of
+   the essential elements of the [T.30] communication protocol are
+   preserved and there is minimal elongation of the session as compared
+   to Group 3 fax over the GSTN.
+
+   These modes are different in the end-user expectation of immediacy,
+   reliability, and in the ease of total compatibility with legacy or
+   traditional facsimile terminals; the modes may have different
+   requirements on operational infrastructure connecting sender and
+   recipient.
+
+3. Goals for Internet Fax
+
+   Facsimile over the Internet must define the mechanisms by which a
+   document is transmitted from a sender to a recipient, and must {1}
+   specify the following elements:
+
+      - Transmission protocol: what Internet protocol(s) and extensions
+        are used?  What options are available in that transmission?
+
+      - Data formats: what image data representation(s) are used,
+        appropriate, required, within the transmission protocol? What
+        other data representations are supported?
+
+      - Addressing: How are Internet Fax recipients identified? How may
+        recipient identification be represented in user directories? How
+        are traditional fax terminals addressed?
+
+
+
+
+
+
+Masinter                     Informational                      [Page 8]
+
+RFC 2542         Terminology and Goals for Internet Fax       March 1999
+
+
+      - Capabilities: The capabilities of the sender to generate
+        different kinds of image data representations may be known to
+        the recipient, and the capabilities, preferences, and
+        characteristics of the recipient may be known to the sender. How
+        are the capabilities, preferences, and characteristics of
+        senders and recipients expressed, and communicated to each
+        other?
+
+      - Security: Faxes may be authenticated as to their origin, or
+        secured to protect the privacy of the message.  How may the
+        authenticity of a fax be determined by the recipient?  How may
+        the privacy of a message be guaranteed?
+
+   Specific goals for these elements are described in section 5.
+
+4. Operational Goals for Internet Fax
+
+   This section lists the necessary and desirable traits of an Internet
+   Fax protocol.
+
+4.1 Functionality
+
+   Traditionally, images sent between fax machines are transmitted over
+   the global switched telephone network. An Internet Fax protocol must
+   {1} provide for a method to accomplish the most commonly used
+   features of traditional fax using only Internet protocols. It is
+   desirable {3} for Internet Fax to support all standard features and
+   modes of standard facsimile.
+
+4.2 Interoperability
+
+   It is essential {1} that Internet Fax support interoperability
+   between most of the devices and applications listed in section 2, and
+   desirable {3} to support all of them. To "support interoperability"
+   means that a compliant sender attempting to send to a compliant
+   recipient will not fail because of incompatibility.
+
+   Overall interoperability requires {1} interoperability for all of the
+   protocol elements: the image data representations must be understood,
+   the transport protocol must function, it must be possible to address
+   all manner of terminals, the security mechanism must not require
+   manual operations in devices that are intended for unattended
+   operation, and so forth.
+
+   Interoperability with Internet mail user agents is a requirement {1}
+   only for the "store-and-forward" facsimile, although it would be
+   useful {3} for "session" and "real-time" modes of delivery of
+   Internet Fax.
+
+
+
+Masinter                     Informational                      [Page 9]
+
+RFC 2542         Terminology and Goals for Internet Fax       March 1999
+
+
+   The requirement for interoperability has strong implications for the
+   protocol design. Interoperability must not {1} depend on having the
+   same kind of networking equipment at each end.
+
+   As with most Internet application protocols, interoperability must
+   {1} be independent of the nature of the networking link, whether a
+   simple IP-based LAN, an internal private IP networks, or the public
+   Internet.  The standard for Internet Fax must {1} be "global": that
+   is, a single specification which does not have or require special
+   features of the transport mechanism for local operations.
+
+   If Internet Fax is to use the Internet mail transport mechanisms, it
+   must {1} interoperate consistently with the current Internet mail
+   environment, and, in particular, with the non-terminal devices listed
+   in section 2.4.4.  If Internet Fax messages might arrive in user's
+   mailboxes, it is required {1} that the protocol interoperate
+   successfully with common user practices for mail messages: storing
+   them in databases, retransmission, forwarding, creation of mail
+   digests, replay of old messages at times long after the original
+   receipt, and replying to messages using non-fax equipment.
+
+   It is desirable {3} that the Internet Fax standard support and
+   facilitate universal messaging systems described in section 2.4.5.
+
+   If Internet Fax requires additions to the operational environment
+   (services, firewall support, gateways, quality of service, protocol
+   extensions), then it is preferable {3} if those additions are useful
+   for other applications than Fax. Features shared with other messaging
+   applications (voice mail, short message service, paging, etc.) are
+   desirable {3}, so as not to require different operational changes for
+   other applications.
+
+4.3 Confirmation
+
+   In almost all applications of traditional fax, it is considered very
+   important that the user can get an assurance that the transmitted
+   data was received by a terminal at the address dialed by the user.
+
+   This goal translates to the Internet environment. The 'Internet Fax'
+   application must {1} define the mechanisms by which a sender may
+   request notification of the completion of transmission of the
+   message, and receive a determinate response as to whether the message
+   was delivered, not delivered, or that no confirmation of delivery is
+   possible.
+
+   Originally, fax "confirmation" implied that the message was received
+   and processed, e.g., delivered to the output paper tray of the
+   recipient fax device.  In reality, this implication was relying upon
+
+
+
+Masinter                     Informational                     [Page 10]
+
+RFC 2542         Terminology and Goals for Internet Fax       March 1999
+
+
+   a signal produced by the receiving terminal that the incoming page
+   had been inspected and was determined to be of reasonable (or
+   unacceptable) quality, via an unspecified algorithm.
+
+   In later devices which support error correction mode, the ECM method
+   (per [T.30]) enabled error checking via a specific algorithm,
+   providing a more exact indication that the bits within the compressed
+   image were not corrupted during transmission.  With the addition of
+   memory buffering, PC-based fax modems and the more common use of
+   error correction mode, traditional fax confirmation still implies
+   some assurance of processability; (e.g., a fax modem would not be
+   able to receive an incoming fax if it required compression mechanisms
+   that were not supported) without reporting on whether the image has
+   been printed or viewed.
+
+   Consequently, the fax confirmation is not the same as a confirmation
+   that the message was "read": that a human had confirmed that the
+   message was received. It is desirable {3}, but not required, that
+   Internet Fax support confirmation that a message has been read (above
+   and beyond the confirmation that the message has been delivered).
+
+4.4 Quick Delivery
+
+   In many cases, fax transmission is used for delivery of documents
+   where there is a strong user requirement for timeliness, with some
+   guarantees that if transmission begins at all, it will complete
+   quickly. For example, it is a common practice to fax documents for
+   discussion to other participants in a telephone conference call prior
+   to the call.
+
+   Internet Fax should {2} allow the sender of a document to request
+   immediate delivery, if such delivery is possible. In such cases, it
+   should {2} be possible for the sender of a message to avoid sending
+   the message at all, if quick delivery is not available for a
+   particular recipient.
+
+   It is desirable {3} to have the protocol for requesting quick
+   delivery be the same as, or similar to, the protocol for delayed
+   delivery, so that two separate mechanisms are not required.
+
+   For real-time fax delivery, immediate delivery is the norm, since the
+   protocol must guarantee that when the session connecting sender to
+   recipient has terminated, the message has been delivered to the
+   ultimate recipient.
+
+
+
+
+
+
+
+Masinter                     Informational                     [Page 11]
+
+RFC 2542         Terminology and Goals for Internet Fax       March 1999
+
+
+4.5 Capabilities: reliable, upgrade possible
+
+   Traditionally, facsimile has guaranteed interworking between senders
+   and recipients by having a strict method of negotiation of the
+   capabilities between the two devices. The image representation of
+   facsimile originally was a relatively low resolution, but has
+   increasingly offered additional capabilities (higher resolution,
+   color) as options.
+
+   The use of fax has grown in an evolving world (from 'Group 1' and
+   'Group 2', to 'Group 3' facsimile) because of two elements: (a) a
+   useful baseline of capabilities that all terminals implemented, and
+   (b) the use of capabilities exchange to go beyond that.
+
+   To accommodate current use as well as future growth, Internet Fax
+   should {2} have a simple minimum set of required features that will
+   guarantee interoperability, as well as a mechanism by which higher
+   capability devices can be deployed into a network of lower capability
+   devices while ensuring interoperability.  If recipients with minimum
+   capabilities were, for example, to merely drop non-minimum messages
+   without warning, the result would be that no non-minimum message
+   could be sent reliably. This situation can be avoided in a variety of
+   ways, e.g., through communication of recipient capabilities or by
+   sending multiple renditions.
+
+   The exchange of capabilities in Internet Fax should {2} be robust. To
+   accomplish this, recipients should {2} be encouraged to provide
+   capabilities, even while senders must {1} have a way to send messages
+   to recipients whose capabilities are unknown.
+
+   Even minimum-capability recipients of messages should {2} be required
+   to provide a capability indication in some reliable way. This might
+   be accomplished by providing an entry in a directory service, by
+   offering automatic or semi-automatic replies, or by sending some
+   indication of in a reply to a message with multiple renditions, or as
+   an addition to a negative acknowledgement requiring retransmission.
+
+   On the other hand, for reliability, senders cannot rely on capability
+   information of recipients before transmission. That is, for
+   reliability, senders should {2} have an operational mode which can
+   function when capabilities are not present, even when recipients must
+   always provide capabilities.
+
+4.6 Simplicity
+
+   Internet Fax should not {2} require terminals to possess a large
+   amount of processing power, and a base level implementation must {1}
+   interoperate, even if it does not offer complex processing.
+
+
+
+Masinter                     Informational                     [Page 12]
+
+RFC 2542         Terminology and Goals for Internet Fax       March 1999
+
+
+   Internet Fax should {2} allow interoperability with recipient devices
+   which have limited buffering capabilities and cannot buffer an entire
+   fax message prior to printing, or cannot buffer an entire set of fax
+   pages before beginning transmission of scanned pages.
+
+   Different operational modes (real-time, session, store and forward)
+   might use different protocols, in order to preserve the simplicity of
+   each.
+
+   It is preferable {3} to make as few restrictions and additions to
+   existing protocols as possible while satisfying the other
+   requirements.  It is important {2} that it be possible to use
+   Internet Fax end-to-end in the current Internet environment without
+   any changes to the existing infrastucture, although some features may
+   require adoption of existing standards.
+
+4.7 Security: Cause No Harm, Allow for privacy
+
+   The widespread introduction of Internet Fax must {1} not cause harm,
+   either to its users or to others. For example, an automatic mechanism
+   for returning notification of delivery or capabilities of fax
+   recipients by email must {1} not expose the users or others to mail
+   loops, bombs, or replicated delivery. Automatic capability exchange
+   based on email might not be sufficiently robust and, without
+   sufficient precautions, might expose users to denial of service
+   attacks, or merely the bad effects of errors on the part of system
+   administrators.  Similar considerations apply in these areas to those
+   that have been addressed by work on electronic mail receipt
+   acknowledgements [RFC 2298].
+
+   Internet Fax should {2} not, by default, release information that the
+   users consider private, e.g., as might be forthcoming in response to
+   a broadcast requests for capabilities to a company's Internet fax
+   devices. Public recipients of Internet Fax (e.g., public agencies
+   which accept facsimile messages) should {2} not be required to
+   broadcast messages with capability statements to all potential
+   senders in order to receive facsimile messages appropriate for the
+   capabilities of their device.
+
+   The possibility for "causing harm" might be created by a combination
+   of facilities and other features which individually may be viewed as
+   harmless. Thus, the overall operation of a network full of Internet
+   Fax devices must {1} be considered.
+
+   Interoperation with ITU defined T.30 fax security methods, as well as
+   standard Internet e-mail security methods is desirable {3}.
+
+
+
+
+
+Masinter                     Informational                     [Page 13]
+
+RFC 2542         Terminology and Goals for Internet Fax       March 1999
+
+
+4.8 Reliability
+
+   The Internet Fax protocol should {2} operate reliably over a variety
+   of configurations and situations.
+
+   In particular, operations which rely on time-delayed information
+   might result in inconsistent information, and the protocol should be
+   robust even in such situations.
+
+   For example, in a store-and-forward message environment, the
+   capabilities and preferences of a fax recipient might be used by the
+   sender to construct an appropriate message, e.g., sending a color fax
+   to a color device but a black and white fax to a device that does not
+   have color capability. However, the information about recipient
+   capabilities must be accessible to the sender even when the recipient
+   cannot be contacted directly. Thus, the sender must access recipient
+   capabilities in some kind of storage mechanism, e.g., a directory.  A
+   directory of recipient capabilities is a kind of distributed
+   database, and would be subject to all of the well-known failure modes
+   of distributed databases. For example, update messages with
+   capability descriptions might be delivered out of order, from old
+   archives, might be lost, non-authenticated capability statements
+   might be spoofed or widely distributed by malicious senders. The
+   Internet Fax protocol should {2} be robust in these situations;
+   messages should {2} not be lost or misprocessed even when the
+   sender's knowledge of recipient capabilities are wrong, and robust
+   mechanisms for delivery of recipient capabilities should {2} be used.
+
+4.9 User Experience
+
+   The primary user experience with fax is:
+
+      immediate delivery
+      delivery confirmation
+      ease of use
+
+   The primary user experience with email is:
+
+      delayed delivery
+      no delivery confirmation
+      ability to reply to sender
+      easy to send to multiple recipients
+
+   An Internet Fax standard should {2} attempt to reconcile the
+   differences between the two environments.
+
+
+
+
+
+
+Masinter                     Informational                     [Page 14]
+
+RFC 2542         Terminology and Goals for Internet Fax       March 1999
+
+
+4.10 Legal
+
+   An Internet Fax standard should {2} accomodate the legal requirements
+   for facsimile, and attempt to support functionality similar to that
+   legally required even for devices that do not operate over the public
+   switched telephone network.
+
+   The United States Federal Communication Commission regulations
+   (applicable only within the USA) state:
+
+      Identification Required on Fax Messages
+
+      The FCC's rules require that any message sent to a fax machine
+      must clearly mark on the first page or on each page of the
+      message:
+
+        *     the date and time the transmission is sent;
+        *     the identity of the sender; and
+        *     the telephone number of the sender or of the sending fax
+              machine.
+
+      All fax machines manufactured on or after December 20, 1992 and
+      all facsimile modem boards manufactured on or after December 13,
+      1995 must have the capability to clearly mark such identifying
+      information on the first page or on each page of the
+      transmission."
+
+5. Functional Goals for Internet Fax
+
+   These goals for specific elements of Internet Fax follow from the
+   operational goals described in section 4.
+
+5.1 Goals for image and other data representations
+
+   Interoperability with Internet Mail or other transmission mechanisms
+   that cause data files to appear in Internet terminal environments
+   requires {1} that Internet Fax use a format for images that is in
+   wide use.
+
+   Interoperability with Internet Mail requires {2} that Internet Fax
+   recipients handle those message types that are common in the email
+   environment, including a minimum set of MIME mail formats.
+
+   Interoperability with traditional fax terminals requires {1} that the
+   data format be capable of representing the commonly used compression
+   mechanisms defined for traditional facsimile; support for _all_
+   standard formats defined for traditional facsimile is highly
+   desirable {2}. In addition, interoperability with 'private use'
+
+
+
+Masinter                     Informational                     [Page 15]
+
+RFC 2542         Terminology and Goals for Internet Fax       March 1999
+
+
+   facsimile messages suggests {3} that the standard accommodate
+   arbitrary bit sequences.
+
+5.2 Goals for transmission
+
+   It is necessary {1} that Internet Fax to work in the context of the
+   current Internet, Intranet, and the combination across firewalls.
+
+   A single protocol with various extensions is preferable {3} to
+   multiple separate protocols, if there are devices that might require,
+   at different times and for different recipients, different protocols.
+
+5.3 Goals for addressing
+
+   Interoperability with the terminal types in section 2 requires {1}
+   the ability to address each of the kinds of recipient devices.  The
+   address of a recipient must give sufficient information to allow the
+   sender to initiate communication.
+
+   Interoperability with offramps to legacy fax terminals requires {1}
+   that the message contain some way of addressing the final destination
+   of facsimile messages, including telephone numbers, various ISDN
+   addressing modes, and facsimile sub-addresses.
+
+   Interoperability with Internet Mail requires {1} that it be possible
+   to address Internet Fax to any email address.  Interworking with
+   Internet mail also requires {1} that the addressing is in the email
+   addressing headers, including mail transport envelope [RFC1123] and
+   RFC822 headers, as appropriate. The information must {1} appear
+   nowhere else.
+
+   Sending devices might not have local storage for directories of
+   addresses, and addresses might be cumbersome for users to type in.
+   For these reasons, Internet Fax devices may require configuration to
+   locate directories of recipients and their capabilities.
+
+   The source of a fax message must {1} be clearly identified. The
+   address of the appropriate return message (whether via fax or via
+   email) should {2} be clearly identified in a way that is visible to
+   all manner of recipients.  In the case of Internet Fax delivered by
+   email, it should {2} be possible to use the normal 'reply' functions
+   for email to return a message to the sender.
+
+   Traditionally, it is common for the first page of a fax message sent
+   to a facsimile terminal to contain an (image) representation of the
+   name, address, return number, etc. of the sender of the document.
+   Some legal jurisdictions for facsimile require an identification of
+   the sender on every page. The standard for Internet Fax should {2}
+
+
+
+Masinter                     Informational                     [Page 16]
+
+RFC 2542         Terminology and Goals for Internet Fax       March 1999
+
+
+   cover the issues of sender and recipient identification in the cases
+   where fax messages are re-routed, forwarded, sent through gateways.
+
+5.4 Goals for Security
+
+   Users typically use GSTN-based fax for confidential document
+   transmission, assuming a similar or higher level of confidentiality
+   and protection from both deliberate and inadvertent eavesdropping as
+   holds for telephone conversations; the higher level of
+   confidentiality arising from the requirement for non-standard
+   equipment to intercept and interpret an overheard fax transmission.
+
+   Similarly, in traditional fax there is an expectation (and, in some
+   contexts, a legally recognized assurance) that the received fax is
+   unaltered from the document originally transmitted.
+
+   It is important {2} that Internet Fax give users a level of assurance
+   for privacy and integrity that is as good or better than that
+   available for telephone-based fax.  The Internet Fax standard should
+   {2} specify how secure messages can be sent, in an interoperable
+   fashion. The Internet Fax protocol should {2} encourage the
+   introduction of security features, e.g., by requiring that minimum
+   capability devices still accept signed messages (even if ignoring the
+   signature.)
+
+   In the case where the sender is responsible for payment for offramp
+   services in a remote location, it is desirable {3} to provide for
+   authentication and authorization of the sender, as well as enable
+   billing related information from the offramp to be transferred
+   securely.
+
+5.5 Goals for capabilities exchange
+
+   Traditional fax supports a wide range of devices, including high
+   resolution ("Superfine"); recent enhancements include methods for
+   color and a variety of compression mechanisms. Fax messaging includes
+   the capability for "non-standard frames", which allow vendors to
+   introduce proprietary data formats. In addition, facsimile supports
+   "binary file transfer": a method of sending arbitrary binary data in
+   a fax message.
+
+   To support interoperability with these mechanisms, it should {2} be
+   possible to express a wide variety of fax capabilities.
+
+   Capability support has three elements: expression of the capabilities
+   of the sender (as far as a particular message is concerned),
+   expressing the capabilities of a recipient (in advance of the
+   transmission of the message), and then the protocol by which
+
+
+
+Masinter                     Informational                     [Page 17]
+
+RFC 2542         Terminology and Goals for Internet Fax       March 1999
+
+
+   capabilities are exchanged.
+
+   The Internet Fax standard should {2} specify a uniform mechanism for
+   capabilities expression. If capabilities are being sent at times
+   other than the time of message transmission, then capabilities should
+   {2} include sufficient information to allow it to be validated,
+   authenticated, etc.
+
+   The Internet Fax standard may {3} include one or several methods for
+   transmission, storage, or distribution of capabilities.
+
+   A request for capability information, if sent to a recipient at any
+   time other than the immediate time of delivery of the message, should
+   {2} clearly identify the sender, the recipient whose capabilities are
+   being requested, and the time of the request. Som kind of signature
+   would be useful, too.
+
+   A capability assertion (sent from recipient to sender) should {2}
+   clearly identify the recipient and some indication of the date/time
+   or range of validity of the information inside. To be secure,
+   capability assertions should {2} be protected against interception
+   and the substitution of valid data by invalid data.
+
+6. Security Considerations
+
+   This document describes the goals for the Internet Fax protocol,
+   including the security goals. An Internet Fax protocol must {1}
+   address the security goals and provide adequate measures to provide
+   users with expected security features.
+
+7. Acknowledgements
+
+   The author gratefully acknowledges the contributions of Graham Klyne,
+   Vivian Cancio, Dan Wing, Jim Dahmen, Neil Joffe, Mike Lake, Lloyd
+   McIntyre, Richard Shockey, Herman Silbiger, Nadesan Narenthiran,
+   George Pajari and Dave Crocker for their valuable comments on this
+   document.
+
+8. Author's Address
+
+   Larry Masinter
+   Xerox Corporation
+   3333 Coyote Hill Road
+   Palo Alto, CA 94304
+
+   http://www.parc.xerox.com/masinter
+   Fax: (650) 812-4333
+   EMail: masinter@parc.xerox.com
+
+
+
+Masinter                     Informational                     [Page 18]
+
+RFC 2542         Terminology and Goals for Internet Fax       March 1999
+
+
+9. References
+
+   [T.30]    "Procedures for Document Facsimile Transmission in the
+             General Switched Telephone Network", ITU-T (CCITT),
+             Recommendation T.30, July, 1996.
+
+   [F.185]   "Internet facsimile: Guidelines for the support of the
+             communication of facsimile documents", ITU-T (CCITT),
+             Recommendation F.185, 1998.
+
+   [T.37]    "Procedures for the transfer of facsimile data via store-
+             and-forward on the Internet", ITU-T (CCITT), Recommendation
+             T.37, 1998.
+
+   [T.38]    "Procedures for real time Group 3 facsimile communication
+             between terminals using IP Networks", ITU-T (CCITT),
+             Recommendation T.38, 1998.
+
+   [RFC2305] Toyoda, K., Ohno, H., Murai, J. and D. Wing, "A Simple Mode
+             of Facsimile Using Internet Mail", RFC 2305, March 1998.
+
+   [RFC2298] Fajman, R., "An Extensible Message Format for Message
+             Disposition Notifications", RFC 2298, March 1998.
+
+   [RFC1123] Braden, R., "Requirements for Internet hosts - Application
+             and Support", STD 3, RFC 1123, October 1989.
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+Masinter                     Informational                     [Page 19]
+
+RFC 2542         Terminology and Goals for Internet Fax       March 1999
+
+
+10.  Full Copyright Statement
+
+   Copyright (C) The Internet Society (1999).  All Rights Reserved.
+
+   This document and translations of it may be copied and furnished to
+   others, and derivative works that comment on or otherwise explain it
+   or assist in its implementation may be prepared, copied, published
+   and distributed, in whole or in part, without restriction of any
+   kind, provided that the above copyright notice and this paragraph are
+   included on all such copies and derivative works.  However, this
+   document itself may not be modified in any way, such as by removing
+   the copyright notice or references to the Internet Society or other
+   Internet organizations, except as needed for the purpose of
+   developing Internet standards in which case the procedures for
+   copyrights defined in the Internet Standards process must be
+   followed, or as required to translate it into languages other than
+   English.
+
+   The limited permissions granted above are perpetual and will not be
+   revoked by the Internet Society or its successors or assigns.
+
+   This document and the information contained herein is provided on an
+   "AS IS" basis and THE INTERNET SOCIETY AND THE INTERNET ENGINEERING
+   TASK FORCE DISCLAIMS 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.
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+Masinter                     Informational                     [Page 20]
+