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Network Working Group                                            M. RoseRequest for Comments: 1569                  Dover Beach Consulting, Inc.Category: Informational                                     January 1994Principles of Operation for the TPC.INT Subdomain:Radio Paging -- Technical ProceduresStatus 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 Contents1. Introduction ................................................12. Naming, Addressing, and Routing .............................22.1 Addressing .................................................22.2 Routing ....................................................33. Procedure ...................................................33.1 MAILing versus SENDing .....................................43.2 Latency ....................................................44. Usage Examples ..............................................54.1 MIME-based .................................................54.2 Non-MIME ...................................................55. Security Considerations .....................................66. Acknowledgements ............................................67. References ..................................................68. Author's Address ............................................61.  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.  ConsultRFC1530, "Principles of Operation for the TPC.INT Subdomain: General   Principles and Policy" for overview information.Rose                                                            [Page 1]

RFC 1569          Radio Paging -- Technical Procedures      January 19942.  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 paraphraseRFC 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.Rose                                                            [Page 2]

RFC 1569          Radio Paging -- Technical Procedures      January 19942.2.  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 anRFC 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 numberRose                                                            [Page 3]

RFC 1569          Radio Paging -- Technical Procedures      January 1994   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.Rose                                                            [Page 4]

RFC 1569          Radio Paging -- Technical Procedures      January 1994   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 Examples4.1.  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>     2026282044Rose                                                            [Page 5]

RFC 1569          Radio Paging -- Technical Procedures      January 19945.  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,RFC974, 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.usRose                                                            [Page 6]