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Network Working Group                                            M. RoseRequest for Comments: 1703                  Dover Beach Consulting, Inc.Obsoletes:1569                                             October 1994Category: InformationalPrinciples 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 Alpha-numeric Radio Pagers ................................33.2 Numeric Radio Pagers ......................................43.3 MAILing versus SENDing ....................................43.4 Latency ...................................................54. Usage Examples .............................................54.1 A MIME Example ............................................64.2 A Non-MIME Example ........................................65. Server Configuration Example ...............................66. Security Considerations ....................................87. Acknowledgements ...........................................88. References .................................................89. Author's Address ...........................................91.  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 1703          Radio Paging -- Technical Procedures      October 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.   In addition to a telephone number, a PIN may also be required to   uniquely identify a radio pager.2.1.  Addressing   This number is used to construct the address of a radio paging   server, which forms the recipient address for the message, e.g., one   of:     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@6.7.7.8.0.4.9.5.1.4.1.tpc.int   where "ATOM" is anRFC 822 atom [1], an opaque string for use in   recipient identification when communicating with the paging network,   and 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.)   Note that the mailbox syntax is purposefully restricted in the   interests of pragmatism.  To paraphrase STD 11,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.Rose                                                            [Page 2]

RFC 1703          Radio Paging -- Technical Procedures      October 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   paging 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 paging 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 paging servers were willing to access any   radio pager in that prefix, multiple MX resource records would be   present.  (The DNS servers for the TPC.INT subdomain perform a   rudimentary form of load balancing by rotating the order of the MX   records returned on each query.)   It should be noted that the presence of a wildcard RR which matches a   radio paging 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 paging 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 paging server's electronic mail   address.  The radio paging server begins by looking at the local part   of the address.3.1.  Alpha-numeric Radio Pagers   If the local-part is either "pager.ATOM" or "pager-alpha.ATOM" then   this indicates that the recipient is using an alpha-numeric radio   pager, and ATOM either identifies a paging network (CARRIER), or a   radio pager identity number (PIN), or both, according to these rules:   (1)  if ATOM consists entirely of numeric characters, then ATOM is a        PIN, and the domain-part refers to the IXO access telephone        number for a radio paging carrier; otherwise,Rose                                                            [Page 3]

RFC 1703          Radio Paging -- Technical Procedures      October 1994   (2)  if ATOM does not contain a hyphen character ("-"), then ATOM is        a CARRIER, a local database is consulted to determine the        corresponding IXO access telephone number, and the telephone        number corresponding to the domain-part is used to identify the        radio pager; otherwise,   (3)  if ATOM does contain a hyphen character ("-"), then everything        to the left of the first hyphen is a CARRIER, and everything to        the right of that hyphen is a PIN, a local database is consulted        to determine the corresponding IXO access telephone number, and        the PIN is used is used to identify the radio pager.   If the local-part starts with "pager.", then the message sent to the   radio pager consists of the body of the message; otherwise, if the   local-part starts with "pager-alpha.", then the radio paging server   determines which information in the headers and body of the message   are used when constructing the paging message.  For example, some   radio paging servers might choose to examine the "To" and "Subject"   fields, in addition to the body, whilst other radio paging servers   might choose to simply send the body verbatim.3.2.  Numeric Radio Pagers   If the local-part is the literal string "pager-numeric" then this   indicates that the recipient is using a numeric pager, and the radio   pager dials the telephone number corresponding to the domain-part.   The message sent to the radio pager consists of the body of the   message, which must consist solely of digits.3.3.  MAILing versus SENDing   An SMTP client communicating with a radio paging server may use   attempt either the MAIL or SEND command.  The radio paging 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.Rose                                                            [Page 4]

RFC 1703          Radio Paging -- Technical Procedures      October 1994   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.3.4.  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 paging 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 paging 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 radio paging server will be able to submit   paging requests to the server directly, without additional SMTP-   relaying. That is, transmission from radio paging client to server   will be one "SMTP-hop"only.  This will eliminate any possibility of   non-deterministic delay by the Internet itself.   The combination of configuring radio paging server and 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 paging network.4.  Usage Examples   These examples make use of the "iddd.tpc.int" subdomain.  The DNS   servers for this subdomain, upon encountering a domain of the form:        NUMBER.iddd.tpc.intRose                                                            [Page 5]

RFC 1703          Radio Paging -- Technical Procedures      October 1994   automatically create a CNAME RR of the form:        R.E.B.M.U.N.iddd.tpc.int   e.g.,        14159408776.iddd.tpc.int   will be treated as        6.7.7.8.0.4.9.5.1.4.1.tpc.int4.1.  A MIME Example     To: pager-alpha.98765@18005551234.iddd.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 sent to the radio paging network     having an IXO access telephone number of "+1-8005551234"     to the radio pager having a PIN of "98765".4.2.  A Non-MIME Example     To: pager-numeric@14159408776.iddd.tpc.int     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>     20262820445.  Server Configuration Example   A hypothetical radio paging carrier, e.g.,     Pigeon Paging   might choose to integrate its radio paging services with Internet e-   mail in the following fashion:Rose                                                            [Page 6]

RFC 1703          Radio Paging -- Technical Procedures      October 1994   (1)  The radio paging carrier establishes a top-level domain name,        e.g.,             pigeon.net   (2)  The radio paging carrier installs and operates one or more        radio paging servers, each having a unique entry in the DNS,         e.g.,             ixo1.pigeon.net.              IN A  a.b.c.d        Each of these radio paging servers runs an SMTP server which        implements the SEND command as described inSection 3.3 above.   (3)  The radio paging carrier coordinates with the administrators of        the TPC.INT subdomain to have the appropriate MX records added        to the DNS, assigning cost values in the MX records to reflect        any difference in the quality of service between the radio        paging servers, e.g.,             4.3.2.1.5.5.5.0.0.8.1.tpc.int. IN MX  5 ixo1.pigeon.net.             4.3.2.1.5.5.5.0.0.8.1.tpc.int. IN MX  5 ixo2.pigeon.net.        which would provide both load-balancing and redundancy        (particularly if the servers were located at different points in        the Internet).  At this point, messages can be sent using the        addressing formats described inSection 2.2 above.   (4)  The radio paging carrier may choose to make available a client        program which uses the SMTP SEND command, in order to achieve        "real-time" delivery of messages into the radio paging network.   (5)  Finally, the radio paging carry may choose to assign each of its        customers a mailbox, e.g.,             mrose@pager.pigeon.net        which maps to the TPC.INT address for the customer's radio pager.        The system(s) listed in the DNS for this domain would maintain        the appropriate mail aliases for this mapping, e.g.,             R: 220 pager.pigeon.net SMTP ready             S: HELO malamud.com             R: 220 pager.pigeon.net             S: EXPN mrose             R: 250 <pager-alpha.98765@18005551234.iddd.tpc.int>Rose                                                            [Page 7]

RFC 1703          Radio Paging -- Technical Procedures      October 1994        At the carrier's discretion, these systems may also be the        systems running the radio paging servers.  However, this needn't        be the case.  For example, consider a situation where a client        program which uses the SMTP SEND command, wants to ensure that it        is talking to radio paging server for an address: e.g.,             R: 220 pager.pigeon.net SMTP ready             S: EHLO malamud.com             R: 220-pager.pigeon.net             R: 220 SEND             S: VRFY mrose             R: 551 User not local;                     try <pager-alpha.98765@18005551234.iddd.tpc.int>        or             R: 220 pager.pigeon.net SMTP ready             S: EHLO malamud.com             R: 220-pager.pigeon.net             R: 220 SEND             S: VRFY mrose             R: 250 <pager-alpha.98765@18005551234.iddd.tpc.int>6.  Security Considerations   Internet mail may be subject to monitoring by third parties, and in   particular, message relays.7.  Acknowledgements   This document was motivated byRFC 1568 [6] andRFC 1645 [7].  In   addition, David Crocker, Carl Malamud, and Perry Metzger also   provided substantive comments.8.  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", BBN       Laboratories, STD 14,RFC 974, BBN, January 1986.   [3] Mockapetris, P., "Domain Names -- Concepts and Facilities", STD       13,RFC 1034, USC/Information Sciences Institute, November 1987.   [4] Mockapetris, P., "Domain Names -- Implementation and       Specification", STD 13,RFC 1035, USC/Information Sciences       Institute, November 1987.Rose                                                            [Page 8]

RFC 1703          Radio Paging -- Technical Procedures      October 1994   [5] Borenstein, N., and N. Freed, "MIME: Mechanisms for Specifying       and Describing the Format of Internet Message Bodies",RFC 1521,       Bellcore, Innosoft, September 1993.   [6] Gwinn, A., "Simple Network Paging Protocol - Version 1(b)",RFC1568, Southern Methodist University, January 1994.   [7] Gwinn, A., "Simple Network Paging Protocol - Version 2",RFC1645, Southern Methodist University, July 1994.9.  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 9]