Network Working Group                                            M. Rose
Request for Comments: 1569                  Dover Beach Consulting, Inc.
Category: Informational                                     January 1994

           Principles of Operation for the TPC.INT Subdomain:
                  Radio Paging -- Technical Procedures

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.

Table of Contents

   1. Introduction ................................................    1
   2. Naming, Addressing, and Routing .............................    2
   2.1 Addressing .................................................    2
   2.2 Routing ....................................................    3
   3. Procedure ...................................................    3
   3.1 MAILing versus SENDing .....................................    4
   3.2 Latency ....................................................    4
   4. Usage Examples ..............................................    5
   4.1 MIME-based .................................................    5
   4.2 Non-MIME ...................................................    5
   5. Security Considerations .....................................    6
   6. Acknowledgements ............................................    6
   7. References ..................................................    6
   8. Author's Address ............................................    6

1.  Introduction

   As an adjunct to the usual, two-way electronic mail service, it is at
   times useful to employ a one-way text notification service, called
   radio paging.  This memo describes a technique for radio paging using
   the Internet mail infrastructure.  In particular, this memo focuses
   on the case in which radio pagers are identified via the
   international telephone network.

   The technique described by this memo, mapping telephone numbers to
   domain names, is derived from the TPC.INT subdomain.  Consult RFC
   1530, "Principles of Operation for the TPC.INT Subdomain: General
   Principles and Policy" for overview information.

2.  Naming, Addressing, and Routing

   A radio pager is identified by a telephone number, e.g.,

     +1 415 940 8776

   where "+1" indicates the IDDD country code, and the remaining string
   is a telephone number within that country.

2.1.  Addressing

   This number is used to construct the address of a radio pager server,
   which forms the recipient address for the message, e.g., one of:

     pager-alpha@6.7.7.8.0.4.9.5.1.4.1.tpc.int
     pager-numeric@6.7.7.8.0.4.9.5.1.4.1.tpc.int

   where the domain-part is constructed by reversing the telephone
   number, converting each digit to a domain-label, and being placed
   under "tpc.int." (The telephone number must not include any
   international access codes.)

   In addition, addresses of the form

     pager.ATOM@6.7.7.8.0.4.9.5.1.4.1.tpc.int
     pager-alpha.ATOM@6.7.7.8.0.4.9.5.1.4.1.tpc.int
     pager-numeric.ATOM@6.7.7.8.0.4.9.5.1.4.1.tpc.int

   where "ATOM" is an (optional) RFC 822 atom [1], are reserved for
   future use.  Note that the mailbox syntax is purposefully restricted
   in the interests of pragmatism.  To paraphrase RFC 822, an atom is
   defined as:

     atom    = 1*atomchar

     atomchar=   <any upper or lowercase alphabetic character
                  (A-Z a-z)>
               / <any digit (0-9)>
               / "!" / "#" / "$" / "%" / "&" / "'" / "*" / "+"
               / "-" / "/" / "=" / "?" / "^" / "_" / "`" / "{"
               / "|" / "}" / "~"

   Finally, note that some Internet mail software (especially gateways
   from outside the Internet) impose stringent limitations on the size
   of a mailbox-string.  Thus, originating user agents should take care
   in limiting the local-part to no more than 70 or so characters.

2.2.  Routing

   The message is routed in exactly the same fashion as all other
   electronic mail, i.e., using the MX algorithm [2].  Since a radio
   pager server might be able to access many radio pagers, the
   wildcarding facilities of the DNS [3,4] are used accordingly.  For
   example, if a radio pager server residing at "dbc.mtview.ca.us" is
   willing to access any radio pager with a telephone number prefix of

     +1 415 940

   then this resource record might be present

     *.0.4.9.5.1.4.1.tpc.int.    IN MX 10 dbc.mtview.ca.us.

   Naturally, if several radio pager servers were willing to access any
   radio pager in that prefix, multiple MX resource records would be
   present.

   It should be noted that the presence of a wildcard RR which matches a
   radio pager server's address does not imply that the corresponding
   telephone number is valid, or, if valid, that a radio pager is
   identified by the phone number.  Rather, the presence of a wildcard
   RR indicates that a radio pager server is willing to attempt access.

3.  Procedure

   When information is to be sent to a radio pager, the user application
   constructs an RFC 822 message, containing a "Message-ID" field and a
   textual content (e.g., a "text/plain" content [5]).

   The message is then sent to the radio pager server's electronic mail
   address.

   The radio pager server begins by looking at the local part of the
   address.  If the local-part is the literal string "pager-alpha" then
   this indicates that the recipient is using an alpha-numeric pager.
   The radio pager server consults a local database to determine how to
   send the page based on the domain-part.  This local knowledge
   includes information about the protocol used to talk to the paging
   network and the access number.  As such, a radio pager server will
   register itself in the DNS as providing service only to those phone
   numbers for which it has such knowledge.

   Otherwise, if the local-part is the literal string "pager-numeric"
   then this indicates that the recipient is using a numeric pager.  The
   radio pager server may consult a local database to determine how to
   send the page based on the domain-part; or, it may dial the number

   specified in the domain-part directly.

   For alpha-numeric pagers, the radio pager server determines which
   information found in the headers and body of the message are used
   when constructing the paging message.  For example, some radio pager
   servers might choose to examine the "To" and "Subject" fields, in
   addition to the body, whilst other radio pager servers might choose
   to simply send the body verbatim.

   For numeric pagers, the radio pager server sends only the body, which
   must consistent solely of digits.

3.1.  MAILing versus SENDing

   An SMTP client communicating with a radio pager server may use
   attempt either the MAIL or SEND command.  The radio pager server MUST
   support the MAIL command, and MAY support any of the SEND, SOML, or
   SAML commands.

   If the MAIL command is used, then a positive completion reply to both
   the RCPT and DATA commands indicates, at a minimum, that the message
   has been queued for transmission into the radio paging network for
   the recipient, but is at least queued for transmission into the radio
   paging network.

   If the SEND command is used, then a positive completion reply to both
   the RCPT and DATA commands indicates that the message has been
   accepted by the radio paging network for delivery to the recipient.

   If the SOML or SAML command is used, then a positive completion reply
   to both the RCPT and DATA commands indicates that the message may
   have been accepted by the radio paging network for delivery to the
   recipient.

3.2.  Latency

   Although the Internet electronic mail service tends to perform
   delivery in a timely and reliable manner, some paging services will
   wish to provide a higher degree of assurance to their clients, in
   particular guaranteeing that a positive reply code means that the
   page has been sent on the radio network.  For such requirements, the
   primary constraints are server implementation and client/server
   network connectivity.

   A client that uses the SEND or SAML commands is explicitly requesting
   real-time transmission on the radio network and is requiring that the
   server reply code will carry a statement of success or failure about
   that transmission.

   The IP level of the Internet performs datagram store-and-forward
   service, but gives the end system hosts the appearance of direct
   connectivity, by virtue of allowing interactive service.  The
   Internet electronic mail service adds another layer of store-and-
   forward indirection, so that messages may go through any number of
   relays (and/or gateways).  This may introduce arbitrarily large
   delays of minutes, hours, or days.

   A client that configures their Internet attachment to permit "direct"
   SMTP connectivity to a pager server will be able to submit paging
   requests to the server directly, without additional SMTP-relaying.
   That is, transmission from paging client to paging server will be one
   "SMTP-hop"only.  This will eliminate any possibility of non-
   deterministic delay by the Internet itself.

   The combination of configuring paging server and paging client to
   allow direct IP/SMTP-level interaction and ensuring that they use
   SEND or SAML commands only will mean that a client receiving a
   positive reply from the server is assured that the page has been sent
   on the radio network.

4.  Usage Examples

4.1.  MIME-based

     To: pager-alpha@6.7.7.8.0.4.9.5.1.4.1.tpc.int
     cc: Marshall Rose <mrose@dbc.mtview.ca.us>
     From: Carl Malamud <carl@malamud.com>
     Date: Thu, 22 Jul 1993 08:38:00 -0800
     Subject: First example, for an alphanumeric pager
     Message-ID: <19930908220700.1@malamud.com>
     MIME-Version: 1.0
     Content-Type: text/plain; charset=us-ascii

     A brief textual message.

4.2.  Non-MIME

     To: pager-numeric@6.7.7.8.0.4.9.5.1.4.1.tpc.int
     cc: Marshall Rose <mrose@dbc.mtview.ca.us>
     From: Carl Malamud <carl@malamud.com>
     Date: Thu, 22 Jul 1993 08:38:00 -0800
     Subject: Second example, for a numeric pager
     Message-ID: <19930908220700.2@malamud.com>

     2026282044

5.  Security Considerations

   Internet mail may be subject to monitoring by third parties, and in
   particular, message relays.

6.  Acknowledgements

   This document was motivated by "Simple Network Paging Protocol -
   Version 1", by Allen Gwinn of Southern Methodist University.

   David H. Crocker and Carl Malamud also provided substantive comments.

7.  References

   [1] Crocker, D., "Standard for the Format of ARPA Internet Text
       Messages", STD 11, RFC 822, University of Delaware, August 1982.

   [2] Partridge, C., "Mail Routing and the Domain System", STD 14, RFC
       974, BBN, January 1986.

   [3] Mockapetris, P., "Domain Names -- Concepts and Facilities", STD
       13, RFC 1034, Information Sciences Institute, November 1987.

   [4] Mockapetris, P., "Domain Names -- Implementation and
       Specification", STD 13, RFC 1035, Information Sciences Institute,
       November 1987.

   [5] 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.

8.  Author's Address

   Marshall T. Rose
   Dover Beach Consulting, Inc.
   420 Whisman Court
   Mountain View, CA  94043-2186
   US

   Phone: +1 415 968 1052
   Fax:   +1 415 968 2510
   EMail: mrose@dbc.mtview.ca.us