RFC1703 - Principles of Operation for the TPC.INT Subdomain: Radio Paging -- Tec

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　　Network Working Group M. Rose
Request for Comments: 1703 Dover Beach Consulting, Inc.
Obsoletes: 1569 October 1994
Category: Informational

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 Alpha-numeric Radio Pagers ................................ 3
3.2 Numeric Radio Pagers ...................................... 4
3.3 MAILing versus SENDing .................................... 4
3.4 Latency ................................................... 5
4. Usage Examples ............................................. 5
4.1 A MIME Example ............................................ 6
4.2 A Non-MIME Example ........................................ 6
5. Server Configuration Example ............................... 6
6. Security Considerations .................................... 8
7. Acknowledgements ........................................... 8
8. References ................................................. 8
9. Author's Address ........................................... 9

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.

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 an RFC822 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, RFC822, 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
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 an RFC822 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,

(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.

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.int

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.int

4.1. 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>

2026282044

5. 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:

(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 in Section 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 in Section 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>

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 by RFC1568 [6] and RFC1645 [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, RFC822, University of Delaware, August 1982.

[2] Partridge, C., "Mail Routing and the Domain System", BBN
Laboratories, STD 14, RFC974, BBN, January 1986.

[3] Mockapetris, P., "Domain Names -- Concepts and Facilities", STD
13, RFC1034, USC/Information Sciences Institute, November 1987.

[4] Mockapetris, P., "Domain Names -- Implementation and
Specification", STD 13, RFC1035, USC/Information Sciences
Institute, November 1987.

[5] Borenstein, N., and N. Freed, "MIME: Mechanisms for Specifying
and Describing the Format of Internet Message Bodies", RFC1521,
Bellcore, Innosoft, September 1993.

[6] Gwinn, A., "Simple Network Paging Protocol - Version 1(b)", RFC
1568, Southern Methodist University, January 1994.

[7] Gwinn, A., "Simple Network Paging Protocol - Version 2", RFC
1645, 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

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