Principles of Operation for the TPC.INT Subdomain: Radio Paging -- Technical Procedures
Using Internet email to send pages to radio pagers via phone numbers.
Rose, M., "Principles of Operation for the TPC.INT Subdomain: Radio Paging -- Technical Procedures", RFC 1569, DOI 10.17487/RFC1569, January 1994, <https://www.rfc-editor.org/info/rfc1569>.
@misc{rfc1569,
series = {Request for Comments},
number = 1569,
howpublished = {RFC 1569},
publisher = {RFC Editor},
doi = {10.17487/RFC1569},
url = {https://www.rfc-editor.org/info/rfc1569},
author = {M. Rose},
title = {{Principles of Operation for the TPC.INT Subdomain: Radio Paging -- Technical Procedures}},
pagetotal = 6,
year = 1994,
month = jan,
} RFC text
Contents
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
AI ELI5
On this page
§1Paging via Email
RFC 1569 describes a technique for delivering radio paging messages using Internet mail. Instead of using specialized paging software or protocols, the method integrates radio pagers into the standard email infrastructure by mapping pager phone numbers to email addresses.
The approach is based on the TPC.INT subdomain, a special part of the DNS namespace designed to map telephone numbers to servers. This allows pagers identified by their phone number to receive messages sent through ordinary email, making paging accessible to anyone with an email client.
This memo lets you send a page to someone using email, just by using their pager's phone number in the email address. The email system automatically finds the right pager network and delivers the message.
§2Pager Addresses and the TPC.INT Domain
A radio pager is identified by a telephone number, such as +1 415 940 8776, where "+1" is the country code. This number is transformed into an email address using the TPC.INT subdomain by reversing the digits and converting each to a domain label.
For example, the phone number +1 415 940 8776 becomes the domain 6.7.7.8.0.4.9.5.1.4.1.tpc.int. The local part (the part before the @) specifies the pager type: pager-alpha for alphanumeric pagers, which can display text, or pager-numeric for numeric pagers, which display only numbers.
A complete email address might be pager-alpha@6.7.7.8.0.4.9.5.1.4.1.tpc.int. The DNS uses wildcarding to route messages: a server willing to handle all phone numbers starting with +1 415 940 registers a wildcard MX record like *.0.4.9.5.1.4.1.tpc.int. pointing to itself.
You take the phone number, flip it backwards, put dots between the digits, and add @tpc.int. That becomes the pager's email address. The "pager-alpha" or "pager-numeric" prefix tells the server what kind of pager it is.
- tpc.int
- 1.4.1 (country +1, area 415)
- pager-alpha (alphanumeric)
- pager-numeric (numeric)
- Example: 6.7.7.8.0.4.9.5.1.4.1.tpc.int (phone +1 415 940 8776)
§3How Paging Works
When a paging message is sent via email, the radio pager server receives the email and examines the local-part of the address. For an alphanumeric pager, the server looks at the domain-part to determine which paging network handles that phone number, then consults a local database for protocol and access details specific to that network.
For numeric pagers, the server sends only the message body, which must consist solely of digits. For alphanumeric pagers, the server decides which email headers and body content to include in the page sent to the network; some servers might send just the body, while others include the Subject line.
The RFC distinguishes between the MAIL, SEND, SOML, and SAML SMTP commands. With MAIL, a successful reply means the message is queued for transmission to the paging network. With SEND, success means the network has accepted the message for delivery. This distinction lets senders choose between guaranteed queuing and guaranteed real-time delivery.
The email server looks at the phone number in the address and finds which paging network can reach that pager. It sends the message through that network. For numeric pagers, only numbers in the message are sent; for alphanumeric pagers, text is sent.
- Send email to pager@tpc.int
- Route via MX lookup
- Parse address and message
- Send page via TAP/IXO or SMS
- Deliver to pager
§4Real-Time Paging
Email delivery is reliable but not guaranteed to be fast. Messages can be delayed by network problems, server queues, or mail relays, sometimes for hours. For urgent paging, this is unacceptable.
RFC 1569 addresses this by allowing clients to use the SEND or SAML SMTP commands instead of MAIL. These commands require real-time transmission on the radio network and ask the server to reply with confirmation of success or failure. Combined with direct IP connectivity from the paging client to the paging server (avoiding mail relays), this eliminates the possibility of non-deterministic delays introduced by the Internet mail infrastructure.
The trade-off is that not all servers support these commands, and direct connectivity may not always be possible. But for organizations with the capability, it provides a path to urgent, real-time paging using the familiar email infrastructure.
Normal email can take a long time to arrive. If you need a page right away, you can use special SMTP commands that tell the server to deliver it to the pager immediately and confirm it worked, as long as your email server supports this.
§5Paging Examples
An alphanumeric page might be addressed to pager-alpha@6.7.7.8.0.4.9.5.1.4.1.tpc.int with a Subject line and message body. The radio pager server would read these headers and the body to construct the message sent to the paging network.
A numeric page would be addressed to pager-numeric@6.7.7.8.0.4.9.5.1.4.1.tpc.int with only digits in the message body, since numeric pagers cannot display text. The server reads only the body and sends those digits to the pager.
In both cases, the message is composed as a standard RFC 822 message with a Message-ID field and appropriate content type. The paging server handles the rest, translating the email into the protocol required by the paging network.
You send a normal email to the special pager address. For text pagers, include your message in the body. For numeric pagers, put numbers in the body. The paging server automatically turns that email into a page signal.