rfc1911.txt

来自「RFC 的详细文档！」· 文本 代码 · 共 1,236 行 · 第 1/4 页

Network Working Group                                       G. Vaudreuil
Request for Comments: 1911                        Octel Network Services
Category: Experimental                                     February 1996


                    Voice Profile for Internet Mail

Status of this Memo

   This memo defines an Experimental Protocol for the Internet
   community.  This memo does not specify an Internet standard of any
   kind.  Discussion and suggestions for improvement are requested.
   Distribution of this memo is unlimited.

1. Abstract

   A class of special-purpose computers has evolved to provide voice
   messaging services.  These machines generally interface to a
   telephone switch and provide call answering and voice messaging
   services.  Traditionally, messages sent to a non-local machine are
   transported using analog networking protocols based on DTMF signaling
   and analog voice playback.  As the demand for networking increases,
   there is a need for a standard high-quality digital protocol to
   connect these machines.  The following document is a profile of the
   Internet standard MIME and ESMTP protocols for use as a digital voice
   networking protocol.

   This profile is based on an earlier effort in the Audio Message
   Interchange Specification (AMIS) group to define a voice messaging
   protocol based on X.400 technology.  This protocol is intended to
   satisfy the user requirements statement from that earlier work with
   the industry standard ESMTP/MIME mail protocol infrastructures
   already used within corporate internets.  This profile will be called
   the voice profile in this document.

2. Scope and Design Goals

   MIME is the Internet multipurpose, multimedia messaging standard.
   This document explicitly recognizes its capabilities and provides a
   mechanism for the exchange of various messaging technologies
   including voice and facsimile.

   This document specifies a profile of the TCP/IP multimedia messaging
   protocols for use by special-purpose voice processing platforms.
   These platforms have historically been special-purpose computers and
   often do not have facilities normally associated with a traditional
   Internet Email-capable computer.  This profile is intended to specify
   the minimum common set of features and functionally for conformant



Vaudreuil                     Experimental                      [Page 1]

RFC 1911                   MIME Voice Profile              February 1996


   systems.

   The voice profile does not place limits on the use of additional
   media types or protocol options.  However, systems which are
   conformant to this profile should not send messages with features
   beyond this profile unless explicit per-destination configuration of
   these enhanced features is provided.  Such configuration information
   could be stored in a directory, though the implementation of this is
   a local matter.

   The following are typical limitations of voice messaging platform
   which were considered in creating this baseline profile.

      1) Text messages are not normally received and often cannot be
      displayed or viewed.  They can often be processed only via
      advanced text-to-speech or text-to-fax features not currently
      present in these machines.

      2) Voice mail machines usually act as an integrated Message
      Transfer Agent and a User Agent.  The voice mail machine is
      responsible for final delivery, and there is no relaying of
      messages.  RFC 822 header fields may have limited use in the
      context of the simple messaging features currently deployed.

      3) VM message stores are generally not capable of preserving the
      full semantics of an Internet message.  As such, use of a voice
      mail machine for general message forwarding and gatewaying is not
      supported.  Storage of "Received" lines and "Message-ID" may be
      limited.

      4) Nothing in this document precludes use of a general purpose
      email gateway from providing these services.  However, significant
      performance degradation may result if the email gateway does not
      support the ESMTP options recommended by this document.

      5) Internet-style mailing lists are not generally supported.
      Distribution lists are implemented as local alias lists.

      6) There is generally no human operator.  Error reports must be
      machine-parsable so that helpful responses can be given to users
      whose only access mechanism is a telephone.

      7) The system user names are often limited to 16 or fewer numeric
      characters.  Alpha characters are not generally used for mailbox
      identification as they cannot be easily entered from a telephone
      terminal.





Vaudreuil                     Experimental                      [Page 2]

RFC 1911                   MIME Voice Profile              February 1996


   It is a goal of this effort to make as few restrictions and additions
   to the existing Internet mail protocols as possible while satisfying
   the user requirements for interoperability with current voice
   messaging systems.  This goal is motivated by the desire to increase
   the accessibility to digital messaging by enabling the use of proven
   existing networking software for rapid development.

   This specification is intended for use on a TCP/IP network, however,
   it is possible to use the SMTP protocol suite over other transport
   protocols.  The necessary protocol parameters for such use is outside
   the scope of this document.

   This profile is intended to be robust enough to be used in an
   environment such as the global Internet with installed base gateways
   which do not understand MIME.  It is expected that a messaging system
   will be managed by a system administrator who can perform TCP/IP
   network configuration.  When using facsimile or multiple voice
   encodings, it is expected that the system administrator will maintain
   a list of the capabilities of the networked mail machines to reduce
   the sending of undeliverable messages due to lack of feature support.
   Configuration, implementation and management of this directory
   listing capabilities is a local matter.

   This specification is a profile of the relevant TCP/IP Internet
   protocols.  These technologies, as well as the specifications for the
   Internet mail protocols, are defined in the Request for Comment (RFC)
   document series.  That series documents the standards as well as the
   lore of the TCP/IP protocol suite.  This document should be read with
   the following RFC documents: RFC 821, Simple Mail Transfer Protocol;
   RFC 822, Standard for the format of ARPA Internet Messages; RFC 1521
   and RFC 1522, Multipurpose Internet Mail Extensions; RFC 1651, RFC
   1652, and RFC 1653, SMTP Service Extensions (ESMTP); and RFC 1034 and
   RFC 1035, Domain Name System. Where additional functionality is
   needed, it will be defined in this document or in an appendix.

3. Protocol Restrictions

   This protocol does not limit the number of recipients per message.
   Where possible, implementations should not restrict the number of
   recipients in a single message.  It is recognized that no
   implementation supports unlimited recipients, and that the number of
   supported recipients may be quite low.  However, ESMTP currently does
   not provide a mechanism for indicating the number of supported
   recipients.







Vaudreuil                     Experimental                      [Page 3]

RFC 1911                   MIME Voice Profile              February 1996


   This protocol does not limit the maximum message length.
   Implementors should understand that some machines will be unable to
   accept excessively long messages.  A mechanism is defined in the RFC
   1425 ESMTP extensions to declare the maximum message size supported.

   The message size indicated in the ESMTP SIZE command is in bytes, not
   minutes.  The number of bytes varies by voice encoding format and
   must include the MIME wrapper overhead.  If the length must be known
   before sending, an approximate translation into minutes can be
   performed if the voice encoding is known.

4. Voice Message Interexchange Format

   The voice message interchange format is a profile of the Internet
   Email Protocol Suite.  It requires components from the message format
   standard for Internet messages [RFC822], the Multipurpose Internet
   Message Extensions [MIME], the X.400 gateway specification [X.400],
   and the delivery report specifications [DRPT][STATUS].

4.1 Message Addressing Formats

   The RFC 822 uses the domain name system.  This naming system has two
   components: the local part, used for username or mailbox
   identification; and the host part, used for global machine
   identification.

   The local part of the address shall be an ASCII string uniquely
   identifying a mailbox on a destination system.  For voice messaging,
   the local part is a printable string containing the mailbox ID of the
   originator or recipient.  Administration of this space is expected to
   conform to national or corporate private telephone numbering plans.
   While alpha characters and long mailbox identifiers are permitted,
   most voice mail networks rely on numeric mailbox identifiers to
   retain compatibility with the limited 10 digit telephone keypad.

   For example, a compliant message may contain the address
   [e-mail]. It should be noted that while the example
   mailbox address is based on the North American Numbering Plan, any
   other corporate numbering plan can be used.  The use of the domain
   naming system should be transparent to the user.  It is the
   responsibility of the voice mail machine to lookup the fully-
   qualified domain name (FQDN) based on the address entered by the
   user.  The mapping of dialed address to final destination system is
   generally accomplished through implementation-specific means.

   Special addresses are provided for compatibility with the conventions
   of the Internet mail system and to facilitate testing.  These
   addresses do not use numeric local addresses, both to conform to



Vaudreuil                     Experimental                      [Page 4]

RFC 1911                   MIME Voice Profile              February 1996


   current Internet practice and to avoid conflict with existing numeric
   addressing plans.  Some special addresses are as follows:

   Postmaster@domain

   By convention, a special mailbox named "postmaster" MUST exist on all
   systems.  This address is used for diagnostics and should be checked
   regularly by the system manager. This mailbox is particularly likely
   to receive text messages, which is not normal on a voice processing
   platform; the specific handling of these messages is a individual
   implementation choice.

   Loopback@domain

   A special mailbox name named "loopback" SHOULD be designated for
   loopback testing.  If supported, all messages sent to this mailbox
   MUST be returned back to the address listed in the From: address as a
   new message.  The originating address of the returned address MUST be
   "postmaster" to prevent mail loops.

   These two addresses are RESERVED so they do not conflict with any
   internal addressing plan.

4.2 Message Header Fields

   Internet messages contain a header information block.  This header
   block contains information required to identify the sender, the list
   of recipients, the message send time, and other information intended
   for user presentation.  Except for specialized gateway and mailing
   list cases, headers do not indicate delivery options for the
   transport of messages.

   The following header lines are permitted for use with voice messages.

   From

   The originator's fully-qualified domain address (a mailbox address
   followed by the fully-qualified domain name).  The user listed in
   this field should be presented in the voice message envelope as the
   originator of the message.

   Systems conformant to this profile SHOULD provide the text personal
   name of the sender in a quoted phrase if available.  To facilitate
   storage of the text name in a local dial-by-name cache directory, the
   first and last name MUST be separable.  Text names in voice messages
   MUST be represented in the form "last, first, mi." [822].





Vaudreuil                     Experimental                      [Page 5]

RFC 1911                   MIME Voice Profile              February 1996


     Example:

       From: "User, Joe S." <[e-mail]>

     To

   The TO header contains the recipient's fully-qualified domain
   address.  There may be one or more To: fields in any message.

   Systems conformant to this profile SHOULD provide the text personal
   name of the recipient, if known, in a quoted phrase.  The name MUST
   be in the form "last, first, mi." [822].

     Example:

       To: "User, Sam S." <[e-mail]>

   Cc

   The CC header contains additional recipients' fully-qualified domain
   addresses. Many voice mail systems are not capable of storing or
   reporting the full list of recipients to the receiver.