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rfc:rfc2542

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:
  1. Transmission protocol: what Internet protocol(s) and extensions

are used? What options are available in that transmission?

  1. Data formats: what image data representation(s) are used,

appropriate, required, within the transmission protocol? What

      other data representations are supported?
  1. 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

  1. 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?
  1. 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]

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