summaryrefslogtreecommitdiff
path: root/doc/rfc/rfc2542.txt
diff options
context:
space:
mode:
Diffstat (limited to 'doc/rfc/rfc2542.txt')
-rw-r--r--doc/rfc/rfc2542.txt1123
1 files changed, 1123 insertions, 0 deletions
diff --git a/doc/rfc/rfc2542.txt b/doc/rfc/rfc2542.txt
new file mode 100644
index 0000000..c433e2f
--- /dev/null
+++ b/doc/rfc/rfc2542.txt
@@ -0,0 +1,1123 @@
+
+
+
+
+
+
+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]
+