rfc1645.txt

著名的RFC文档,其中有一些文档是已经翻译成中文的的.

Network Working Group                                           A. Gwinn
Request for Comments: 1645                 Southern Methodist University
Obsoletes: 1568                                                July 1994
Category: Informational


               Simple Network Paging Protocol - Version 2

Status of this Memo

   This memo provides information for the Internet community.  This memo
   does not specify an Internet standard of any kind.  Distribution of
   this memo is unlimited.

Abstract

   This RFC suggests a simple way for delivering both alphanumeric and
   numeric pages (one-way) to radio paging terminals.  Gateways
   supporting this protocol, as well as SMTP, have been in use for
   several months for nationwide paging and messaging.  In addition,
   email filters and SNPP client software for Unix and Windows are
   available at no cost.  Please contact the author for more
   information.

   Earlier versions of this specification were reviewed by IESG members
   and the "822 Extensions" Working Group.  They preferred an alternate
   strategy, as discussed under "Relationship to Other IETF Work",
   below.

1. Introduction

   Beepers are as much a part of computer nerdom as X-terminals
   (perhaps, unfortunately, more).  The intent of Simple Network Paging
   Protocol is to provide a standard whereby pages can be delivered to
   individual paging terminals.  The most obvious benefit is the
   elimination of the need for modems and phone lines to produce
   alphanumeric pages, and the added ease of delivery of pages to
   terminals in other cities or countries.  Additionally, automatic page
   delivery should be somewhat more simplified.

2. System Philosophy

   Radio paging is somewhat taken for granted, because of the wide
   availability and wide use of paging products.  However, the actual
   delivery of the page, and the process used (especially in wider area
   paging) is somewhat complicated.  When a user initiates a page, by
   dialing a number on a telephone, or entering an alphanumeric page
   through some input device, the page must ultimately be delivered to



Gwinn                                                           [Page 1]

RFC 1645                    SNPP - Version 2                   July 1994


   some paging terminal, somewhere.  In most cases, this delivery is
   made using TAP (Telocator Alphanumeric input Protocol, also known as
   IXO).  This protocol can be a somewhat convoluted, and complicated
   protocol using older style ASCII control characters and a non-
   standard checksumming routine to assist in validating the data.

   Even though TAP is widely used throughout the industry, there are
   plans on the table to move to a more flexible "standard" protocol
   referred to as TME (Telocator Message Entry Protocol).  The level two
   enhancements to SNPP (as described below) are intended for use with
   this forthcoming standard.

   However, acknowledging the complexity and flexibility of the current
   protocols (or the lack thereof), the final user function is quite
   simple: to deliver a page from point-of-origin to someone's beeper.
   That is the simple, real-time function that the base protocol
   attempts to address.  Validation of the paging information is left
   completely up to the paging terminal, making an SNPP gateway a direct
   "shim" between a paging terminal and the Internet.

3. Why not just use Email and SMTP?

   Email, while quite reliable, is not always timely.  A good example of
   this is deferred messaging when a gateway is down. Suppose Mary Ghoti
   ([e-mail]) sends a message to Zaphod Beeblebrox's beeper
   ([e-mail]). Hugecompany's gateway to the
   Internet is down causing Mary's message to be deferred.  Mary,
   however, is not notified of this delay because her message has not
   actually failed to reach its destination.  Three hours later, the
   link is restored, and (as soon as sendmail wakes up) the message is
   sent.  Obviously, if Mary's page concerned a meeting that was
   supposed to happen 2 hours ago, there will be some minor
   administrative details to work out between Mary and Zaphod!

   On the other hand, if Mary had used her SNPP client (or simply
   telnetted to the SNPP gateway), she would have immediately discovered
   the network problem.  She would have decided to invoke plan "B" and
   call Zaphod's pager on the telephone, ringing him that way.

   The obvious difference here is not page delivery, but the immediate
   notification of a problem that affects your message. Standard email
   and SMTP, while quite reliable in most cases, cannot be positively
   guaranteed between all nodes at all times, making it less desirable
   for emergency or urgent paging.  This inability to guarantee delivery
   could, whether rightly or wrongly, place the service provider in an
   uncomfortable position with a client who has just received his or her
   emergency page, six hours too late.




Gwinn                                                           [Page 2]

RFC 1645                    SNPP - Version 2                   July 1994


   Another advantage of using a separate protocol for paging delivery is
   that it gives the sender absolute flexibility over what is sent to
   the pager.  For instance, in the paging arena, where messages are
   sent to alphanumeric pagers, it is less desirable to send the
   recipient general header lines from a standard SMTP message.  Much of
   the information is useless, possibly redundant, and a waste of
   precious RF bandwidth.

   Therefore, when implementing an SMTP gateway, the service provider
   should elect to parse out needed information (such as the sender, and
   possibly subject) such to maximize the utility of the transmission.
   Parsing generally means less control over content and format by the
   message originator.  SNPP provides a clean, effective way to send a
   message, as written, to the recipient's pager.

   The other consideration is the relative simplicity of the SNPP
   protocol for manual telnet sessions versus someone trying to manually
   hack a mail message into a gateway.

4. The SNPP Protocol

   The SNPP protocol is a sequence of commands and replies, and is based
   on the philosophy of many other Internet protocols currently in use.
   SNPP has several input commands (the first 4 characters of each are
   significant) that solicit various server responses falling into four
   categories:

    2xx - Successful, continue
    3xx - Begin DATA input (see "DATA" command)
    4xx - Failed with connection terminated
    5xx - Failed, but continue session

   The first character of every server response code is a digit
   indicating the category of response.  The text portion of the
   response following the code may be altered to suit individual
   applications.

   The session interaction is actually quite simple (hence the name).
   The client initiates the connection with the listening server.  Upon
   opening the connection, the server issues a "220" level message
   (indicating the willingness of the server to accept SNPP commands).
   The client passes pager ID information, and a message, then issues a
   "SEND" command.  The server then feeds the information to the paging
   terminal, gathers a response, and reports the success or failure to
   the client.






Gwinn                                                           [Page 3]

RFC 1645                    SNPP - Version 2                   July 1994


4.1 Examples of SNPP Transactions

   The following illustrate examples of client-server communication
   using SNPP.

4.1.1 A Typical Level One Connection

            Client                         Server

    Open Connection               -->
                                  <--  220 SNPP Gateway Ready
    PAGE 5551212                  -->
                                  <--  250 Pager ID Accepted
    MESS Your network is hosed    -->
                                  <--  250 Message OK
    SEND                          -->
                                  <--  250 Message Sent OK
    QUIT                          -->
                                  <--  221 OK, Goodbye

4.1.2 A Typical Level Two, Multiple Transaction

   The following example illustrates a single message sent to two
   pagers.  Using this level protocol, pager-specific options may be
   selected for each receiver by specifying the option prior to issuing
   the "PAGEr" command.  In this example, an alternate coverage area is
   selected for the first pager, while delayed messaging is specified
   for the second.

            Client                         Server

    Open Connection               -->
                                  <--  220 SNPP Server Ready
    COVE 2                        -->
                                  <--  250 Alternate Area Selected
    PAGE 5551212 FOOBAR           -->
                                  <--  250 Pager ID Accepted
    HOLD 9401152300 -0600         -->
                                  <--  250 Delayed Message OK
    PAGE 5552323 XYZZY            -->
                                  <--  250 Pager ID Accepted
    SUBJ Seattle Meeting          -->
                                  <--  250 Message Subject OK
    DATA                          -->
                                  <--  354 Begin Input, End With '.'
    Please meet me tomorrow at    -->
    the Seattle office            -->
                                  <--  250 DATA Accepted



Gwinn                                                           [Page 4]

RFC 1645                    SNPP - Version 2                   July 1994


    SEND                          -->
                                  <--  250 Message Sent OK
    QUIT                          -->
                                  <--  221 OK, Goodbye

4.2 Level 1 Commands

   Level one commands are designed as a minimum implementation of the
   protocol.  This collection of commands may be used with either
   TAP/IXO or TME for message delivery to the paging terminal.

4.2.1 PAGEr <Pager ID>

   The PAGEr command submits a pager ID (PID) number, for inclusion in
   the next messaging transaction.  The PID used must reside in, and be
   validated by the paging terminal.  Limited validation may optionally
   be done on the server (such as all numeric, and ID length), or
   validation can be left up to the terminal at the time the page is
   sent.

   When implementing SNPP, the user may elect to support multiple
   recipients per message sent.  However, be wary that validation-
   prior-to-sending is not possible with TAP/IXO (and is not an official
   option of the current TME specification).  What this means is that in
   order to validate a PID, one must generate a message to the pager.
   The terminal responds favorably or negatively.  When reporting
   failure of a single PID in a sequence, delineating and reporting the
   failure in a "standard format" may prove to be a challenge.

   Possible responses from the SNPP server, with suggested text, in
   response to a PAGEr command are:

    250 Pager ID Accepted
    421 Too Many Errors, Goodbye (terminate connection)
    421 Gateway Service Unavailable (terminate connection)
    550 Error, Invalid Pager ID
    554 Error, failed (technical reason)

   The level 2 enhancements affect the PAGEr command.  Please refer to
   the appropriate section for details.

4.2.2 MESSage <Alpha or Numeric Message>

   The MESSage command specifies a single-line message, into the
   gateway.  Limited validation of the message may be done on the SNPP
   server (such as length), but type-of-message validation should be
   done by the paging terminal.  Duplicating the MESSage command before
   SENDing the message should produce an "503 ERROR, Message Already



Gwinn                                                           [Page 5]