rfc2542.txt

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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.







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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.



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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}.





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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.






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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'



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