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

           Simple Network Paging Protocol - Version 1(b)

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.


 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 in one nationwide paging firm.  One other paging firm
 is in the process of adopting it.
 Earlier versions of this specification were reviewed by IESG members
 and the IETF's "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 (SNPP) 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 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
 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

Gwinn [Page 1] RFC 1568 SNPP - Version 1(b) January 1994

 protocol using older style ASCII control characters and a non-
 standard checksumming routine to assist in validating the data.  One
 note: even though the TAP protocol allows for a password for sending
 simple pages, they are rarely used (especially in commercial
 markets), and therefore support for them has not been implemented in
 this version of the protocol.
 Even though TAP is widely used throughout the industry, there are
 plans on the table to move to a more flexible "standard" protocol
 (the proposal for which is actually more convoluted than most
 Internet RFC's).  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
 this protocol attempts to address.  Validation of the paging
 information is left completely up to the TAP/IXO 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
 ( sends a message to Zaphod Beeblebrox's beeper
 ( 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.  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.

Gwinn [Page 2] RFC 1568 SNPP - Version 1(b) January 1994

4. The Future of SNPP

 While the current form of the SNPP protocol is designed for use with
 TAP/IXO, it is intended to provide a porting base for use with the
 newer TME (TDP) protocol.  In addition, future releases of SNPP will
 allow for multiple recipient messages with individual "envelope"
 options and specifications as allowed by TME.  For example, the
 protocol should allow the user to specify delivery of an urgent
 message to Zaphod in Denver, while carbon-copying Mary in Des Moines
 at a lower priority.

5. The 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 six input commands (the first 4 characters of each are
 significant) that solicit various server responses falling into three
 categories: (1) successful, (2) failed-but-continue, and (3) failed-
 with-connection-terminated.  The first character of every server
 response code is a digit indicating the category of response: '2xx',
 '5xx', and '4xx' respectfully.  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 greeting followed by "250
 READY" (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 TAP paging terminal, gathers a response, and reports the
 success or failure to the client.

6.1 A Typical Successful Connection

         Client                         Server
 Open Connection            -->
                            <--  220 SNPP Gateway Ready
 PAGE 5551212               -->
                            <--  250 OK
 MESS Your network is hosed -->
                            <--  250 OK
 SEND                       -->
                            <--  250 Page Sent
 QUIT                       -->
                            <--  221 OK, Goodbye

Gwinn [Page 3] RFC 1568 SNPP - Version 1(b) January 1994

6.2 Commands

6.2.1 PAGEr <Pager ID>

 The PAGEr command sets the pager ID (PID) number, for the
 transaction, into the gateway.  The PID used must reside in the TAP
 terminal (and there is where it should be validated).  Limited
 validation may optionally be done on the server (such as all numeric,
 and ID length), or it can all be done by the TAP terminal at the time
 the page is sent.  Duplicating the PAGEr command before SENDing the
 message should produce an "503 ERROR, Already Entered" message, and
 allow the user to continue.
 In the future, a series of PAGEr commands may be specified to allow
 for multiple recipients of the same message.  Right now, however,
 TAP/IXO only validates the PID at the time the message is accepted by
 the paging terminal.  This makes "pre" validation of PID's currently

6.2.2 MESSage <Alpha or Numeric Message>

 The MESSage command sets the numeric or alphanumeric message for the
 transaction, 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 TAP/IXO paging terminal.
 Duplicating the MESSage command before SENDing the message should
 produce an "503 ERROR, Already Entered" message, and allow the user
 to continue.

6.2.3 RESEt

 The RESEt command clears the PAGEr and MESSage fields, and allows the
 client to start over.  This is provided, primarily, as a means to
 reset accidentally entered information during a manual session. Upon
 a successful reset, the server should respond "250 RESET OK".

6.2.4 SEND

 The SEND command processes the page to the TAP terminal.  Prior to
 processing, the PAGEr and MESSage fields should be checked for the
 existence of information.  Should one of these required fields be
 missing, the server should respond "503 Error, Incomplete
 Information" and allow the user to continue.  Assuming all of the
 fields are filled in, the SNPP server should format and send the page
 to the TAP terminal, and await a response.  Upon receiving a reply,
 the server should respond as follows:

Gwinn [Page 4] RFC 1568 SNPP - Version 1(b) January 1994

  250 Page Sent         - successful delivery
  554 Failed, <reason>  - unsuccessful, and gives a reason
 Or, in the case of an illegal or non-existent pager ID, or some other
 administrative reason for rejecting the page, the server should
  550 Failed, Illegal Pager ID (or other explanation)
 After processing a SEND command, the server should remain online to
 allow the client to enter another page.

6.2.5 QUIT

 The QUIT command terminates the current session.  The server should
 respond "221 OK, Goodbye" and close the connection.

6.2.6 HELP

 The HELP command (optional) displays a screen of information about
 commands that are valid on the SNPP server.  This is primarily to
 assist manual users of the gateway.  Each line of the HELP screen
 (responses) are preceded by a code "214".  At the end of the HELP
 sequence, a "250 OK" is issued.

6.3 Illegal Commands

 Should the client issue an illegal command, the server should respond
 "421 ERROR, Goodbye" and close the connection immediately.
 Optionally, the server may respond "502 Command Error, try again"
 should it be desirable to leave the connection open.

6.4 Timeouts

 The SNPP server can, optionally, have an inactivity timeout
 implemented.  At the expiration of the allotted time, the server
 responds "421 Timeout, Goodbye" and closes the connection.

6.5 Rigidity of Command Structure

 The commands from client to server should remain constant.  However,
 since the first character of the response indicates success or
 failure, the text of the server responses could be altered should one
 desire.  The following is a hunk of C code that is used currently in
 an SNPP gateway.  The only response that has not been discussed is
 "421 SERVER DOWN, Goodbye" and is used when the gateway is
 administratively down, or when there are communication problems with
 the TAP/IXO paging terminal.

Gwinn [Page 5] RFC 1568 SNPP - Version 1(b) January 1994

 /* SNPP Client Commands */
 #define PAGER        "PAGE"
 #define MESSAGE      "MESS"
 #define SEND         "SEND"
 #define QUIT         "QUIT"
 #define RESET        "RESE"
 #define HELP         "HELP"
 /* Responses from SNPP server to client */
 #define SNPP_OK      "250 OK"
 #define SNPP_RESET   "250 Reset OK"
 #define SNPP_SENT    "250 Page Sent"
 #define SNPP_BADPIN  "550 Failed,"
 #define SNPP_NOTSENT "554 Failed,"
 #define SNPP_ENTERR  "503 Error, Already Entered"
 #define SNPP_ERRINC  "503 Error, Incomplete Info"
 #define SNPP_OKCLOS  "221 OK, Goodbye"
 #define SNPP_TIMEOUT "421 Timeout, Goodbye"
 #define SNPP_ERRCLOS "421 ERROR, Goodbye"
 #define SNPP_DOWN    "421 SERVER DOWN, Goodbye"

7. Revision History

 Originally, when proposed, the author employed POP2 style
 result/response codes.  The Internet community suggested that this
 '+' and '-' style theory be altered to provide numeric response codes
 -- similar to those used in other services such as SMTP.  The
 protocol has been altered to this specification from the first
 proposed draft.
 When a bad pager ID message (IXO/TAP administrative failure was
 received from the paging terminal, a 554 series (general failure) was
 returned.  This has been changed to a 550 failure code allowing a
 distinction to be made.

8. Relationship to Other IETF Work

 The strategy of this specification, and many of its details, were
 reviewed by an IETF Working Group and three IESG members.  They
 concluded that an approach using the existing email infrastructure
 was preferable, due in large measure to the very high costs of
 deploying a new protocol and the advantages of using the Internet's
 most widely-distributed applications protocol infrastructure.  Most
 reviewers felt that no new protocol was needed at all because the
 special "deliver immediately or fail" requirements of SNPP could be
 accomplished by careful configuration of clients and servers.  The

Gwinn [Page 6] RFC 1568 SNPP - Version 1(b) January 1994

 experimental network printing protocol [3] was identified as an
 example of an existing infrastructure approach to an existing
 problem.  Other reviewers believed that a case could be made for new
 protocol details to identify paging clients and servers to each other
 and negotiate details of the transactions, but that it would be
 sensible to handle those details as extensions to SMTP [1,2] rather
 than deploying a new protocol structure.
 The author, while recognizing these positions, believes that there is
 merit in a separate protocol to isolate details of TAP/IXO and its
 evolving successors from users and, indeed, from mail-based
 approaches that might reach systems that would act as SMTP/MIME [4]
 to SNPP gateways.  Such systems and gateways are, indeed, undergoing
 design and development concurrent with this work.  See the section
 "Why not just use Email and SMTP?" for additional discussion of the
 author's view of the classical electronic email approach.

9. References

 [1] Postel, J., "Simple Mail Transfer Protocol", STD 10, RFC 821,
     USC/Information Sciences Institute, August 1982.
 [2] Klensin, J., Freed, N., Rose, M., Stefferud, E., and D. Crocker,
     "SMTP Service Extensions", United Nations University, Innosoft,
     Dover Beach Consulting, Inc., Network Management Associates,
     Inc., The Branch Office, February 1993.
 [3] Rose, M., and C. Malamud, "An Experiment in Remote Printing", RFC
     1486, Dover Beach Consulting, Inc., Internet Multicasting
     Service, July 1993.
 [4] Borenstein, N., and N. Freed, "MIME  (Multipurpose Internet Mail
     Extensions) Part One:  Mechanisms for Specifying and Describing
     the Format of Internet Message Bodies", RFC 1521, Bellcore,
     Innosoft, September 1993.

Gwinn [Page 7] RFC 1568 SNPP - Version 1(b) January 1994

10. Security Considerations

 Security issues are not discussed in this memo.

11. Author's Address

 R. Allen Gwinn, Jr.
 Associate Director, Computing Services
 Business Information Center
 Southern Methodist University
 Dallas, TX  75275
 Phone:  214/768-3186
 EMail: or

Gwinn [Page 8]

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