rfc2542.txt

著名的RFC文档,其中有一些文档是已经翻译成中文的的.

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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.







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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.





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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?






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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.



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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



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