RFC1528 - Principles of Operation for the TPC.INT Subdomain: Remote Printing --

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　　Network Working Group C. Malamud
Request for Comments: 1528 Internet Multicasting Service
Obsoletes: 1486 M. Rose
Category: Experimental Dover Beach Consulting, Inc.
October 1993

Principles of Operation for the TPC.INT Subdomain:
Remote Printing -- Technical Procedures

Status of this Memo

This memo defines an Experimental Protocol for the Internet
community. It does not specify an Internet standard. Discussion and
suggestions for improvement are requested. Please refer to the
current edition of the "Internet Official Protocol Standards" for the
standardization state and status of this protocol. Distribution of
this memo is unlimited.

Table of Contents

1. Introduction .......................................... 2
2. Naming, Addressing, and Routing ....................... 2
2.1 Addressing ........................................... 2
2.2 Routing .............................................. 3
3. Procedure ............................................. 3
3.1 Content-Types ........................................ 4
3.2 Generating a Cover-Sheet ............................. 4
3.3 Return Receipt ....................................... 6
4. Usage Examples ........................................ 6
4.1 Explicit Cover Sheet ................................. 6
4.2 Implicit Cover Sheet ................................. 7
4.3 Minimal, Text-only ................................... 7
5. Prototype Implementation .............................. 7
6. Future Issues ......................................... 9
7. Security Considerations ............................... 9
8. Acknowledgements ...................................... 9
9. References ............................................ 9
10. Authors' Addresses .................................. 10
A. The application/remote-printing Content-Type ......... 11
B. The image/tiff Content-Type .......................... 12

1. Introduction

Although electronic mail is preferable as a means of third-party
communication, in some cases it may be necessary to print
information, in hard-copy form, at a remote location. The remote
output device may consist of a standard line printer, a printer with

multiple fonts and faces, a printer that can reproduce graphics, or a
facsimile device. Remote output may be accompanied by information
that identifies the intended recipient. This memo describes a
technique for "remote printing" using the Internet mail
infrastructure. In particular, this memo focuses on the case in
which remote printers are connected to the international telephone
network.

2. Naming, Addressing, and Routing

A printer is identified by a telephone number which corresponds to a
G3-facsimile device connected to the international telephone network,
e.g.,

+1 415 968 2510

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 remote printer
server, which forms the recipient address for the message, e.g.,
either

remote-printer@0.1.5.2.8.6.9.5.1.4.1.tpc.int

or

remote-printer.ATOM@0.1.5.2.8.6.9.5.1.4.1.tpc.int

where "ATOM" is an (optional) RFC822 atom [1], an opaque string for
use in recipient identification when generating a cover-sheet, and
the domain-part is constructed by reversing the telephone number,
converting each digit to a domain-label, and being placed under
"tpc.int."

Note that the mailbox syntax is purposefully restricted in the
interests of pragmatism. To paraphrase 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 remote
printer server might be able to access many printers, the wildcarding
facilities of the DNS [3,4] are used accordingly. For example, if a
remote printer server residing at "dbc.mtview.ca.us" was willing to
access any printer with a telephone number prefix of

+1 415 968

then this resource record might be present

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

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

It should be noted that the presence of a wildcard RR which matches a
remote printer server's address does not imply that the corresponding
telephone number is valid, or, if valid, that a G3-facsimile device
is connected at the phone number.

3. Procedure

When information is to be remotely printed, the user application
constructs an RFC822 message, containing a "Message-ID" field.

If the local-part of the address does not contain an opaque string
for use in recipient identification, then the body must consist
"multipart/mixed" content [5] having at two parts, the first being a
"application/remote-printing" content-type (defined in Appendix A),
which will be used to generate a cover-sheet, and the second being an
arbitrary content-type corresponding to the information to be
printed. If the local-part of the address does contain an opaque
string for use in recipient identification, then the body consists of
an arbitrary content-type corresponding to the information to be
printed.

Regardless, the message is then sent to the remote printer server's
electronic mail address.

3.1 Content-Types

It should be noted that not all content-types have a natural printing
representation, e.g., an "audio" or "video" content. For this
reason, the second part of the "multipart/mixed" content should be
one of the following:

text/plain, message/rfc822, application/postscript image/tiff
(defined in Appendix B), any multipart.

Note that:

(1) With the "text/plain" content-type, not all character
sets may be available for printing.

(2) With the "message" content-type, the subordinate content
will be processed recursively.

(3) With the "application/postscript" content-type, the
remote printer server should evaluate the contents in a
safe execution environment.

(4) With the "multipart" content-type the subordinate contents
will be processed recursively: for a "multipart/mixed" or
"multipart/digest" content, each subordinate content will
start on a new page, whilst for a "multipart/parallel" content,
all subordinate contents will, if possible, start on the same
page. Naturally, when processing a "multipart/alternative"
content, only one subordinate content will be printed.

3.2 Generating a Cover-Sheet

If the "application/remote-printing" content-type is present,
this contains all the information necessary to generate a

cover-sheet. Otherwise, the cover-sheet must be generated
based on other information available.

Typically, a cover sheet consists of three sections:

o information identifying the originator;

o information identifying the recipient; and,

o additional information supplied by the remote printer
server.

To identify the originator, the remote printer server will use the
message headers, usually by stripping any trace headers (i.e.,
"Received" and "Return-Path") and then re-ordering the remaining
headers starting with the "From" header.

To identify the recipient, the opaque string from the local- part of
the remote printer server's address is consulted. For example, if
the remote printer server's address is

remote-printer.Arlington_Hewes/Room_403@0.1.5.2.8.6.9.5.1.4.1.tpc.int

then the opaque string

Arlington_Hewes/Room_403

is consulted. lp When generating a cover-sheet using this opaque
string, the remote printer server will interpret an underscore
character ("_") as a space, and a solidus character ("/") as an end-
of-line sequence. A remote printer server will interpret two
consecutive underscore characters in the opaque string as a single
underscore, and two consecutive solidus characters as a single
solidus. So, the opaque string,

Arlington_Hewes/Room_403

might appear on the cover-sheet as

To: Arlington Hewes
Room 403

3.3 Return Receipt

When the remote printer server finishes its processing, a message is
returned to the originator, indicating either success (i.e., the
message was successfully sent to the facsimile device), or failure,
with an explanation (e.g., after several repeated attempts, there was
no answer).

4. Usage Examples

4.1 Explicit Cover Sheet

To: remote-printer@0.1.5.2.8.6.9.5.1.4.1.tpc.int
From: Carl Malamud <carl@malamud.com>
Date: Thu, 22 Jul 1993 08:38:00 -0800
Subject: First example
Message-ID: <19930722163800.1@malamud.com>
MIME-Version: 1.0
Content-Type: multipart/mixed;
boundary="----- =_aaaaaaaaaa0"

------- =_aaaaaaaaaa0
Content-Type: application/remote-printing

Recipient: Arlington Hewes
Telephone: +1 415 968 1052
Facsimile: +1 415 968 2510

Originator: Carl Malamud
Organization: Internet Multicasting Service
Address: Suite 1155, The National Press Building
Washington, DC 20045
US
Telephone: +1 202 628 2044
Facsimile: +1 202 628 2042
EMail: carl@malamud.com

Any text appearing here would go on the cover-sheet.

------- =_aaaaaaaaaa0
Content-Type: text/plain; charset="us-ascii"

Here are my comments...

------- =_aaaaaaaaaa0--

4.2 Implicit Cover Sheet

To:remote-printer.Arlington_Hewes/Room_403@0.1.5.2.8.6.9.5.1.4.1.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
Message-ID: <19930722163800.2@malamud.com>
MIME-Version: 1.0
Content-Type: application/postscript

%!

Note that in this latter example, both remote printing and e-mail
recipients can be identified in the same message.

4.3 Minimal, Text-only

To:remote-printer.Arlington_Hewes/Room_403@0.1.5.2.8.6.9.5.1.4.1.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: Third example
Message-ID: <19930722163800.3@malamud.com>

Here are my comments...

5. Prototype Implementation

A prototype implementation is openly available. The MIME
instructions for retrieval are:

MIME-Version: 1.0
Content-Type: multipart/alternative;
boundary="----- =_aaaaaaaaaa0"
Content-Description: pointers to ftp and e-mail access

------- =_aaaaaaaaaa0
Content-Type: message/external-body;
access-type="mail-server";
server="archive-server@ftp.ics.uci.edu"

Content-Type: application/octet-stream; type="tar";
x-conversions="x-compress"
Content-ID: <4599.735726126.1@dbc.mtview.ca.us>

mimesend mrose/tpc/rp.tar.Z

------- =_aaaaaaaaaa0
Content-Type: message/external-body;
access-type="anon-ftp"; name="rp.tar.Z";
directory="mrose/tpc"; site="ftp.ics.uci.edu"

Content-Type: application/octet-stream; type="tar";
x-conversions="x-compress"
Content-ID: <4599.735726126.2@dbc.mtview.ca.us>

------- =_aaaaaaaaaa0--

This package contains software for UNIX-based systems, and was
developed and tested under SunOS, with an openly-available facsimile
package (Sam Leffler's FlexFAX package), and contains information for
sites acting as either client or server participants, and zone
administrators.

6. Future Issues

Note that several issues are not addressed, e.g.,

o determining which content-types and character sets are
supported by a remote printer server;

o introduction of authentication, integrity, privacy,
authorization, and accounting services;

o preferential selection of a remote printer server; and,

o aggregation of multiple print recipients in a single
message.

Subsequent work might consider these issues in detail.

7. Security Considerations

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

8. Acknowledgements

This document is based on RFC1486, "An Experiment in Remote
Printing".

9. References

[1] Crocker, D., "Standard for the Format of ARPA Internet Text
Messages", STD 11, RFC822, UDEL, August 1982.

[2] Partridge, C., "Mail Routing and the Domain System" STD 14, RFC
974, CSNET CIC 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 (Multipurpose Internet Mail
Extensions) Part One: Mechanisms for Specifying and Describing
the Format of Internet Message Bodies", RFC1521, Bellcore,
Innosoft, September 1993.

10. Authors' Addresses

Carl Malamud
Internet Multicasting Service
Suite 1155, The National Press Building
Washington, DC 20045
US

Phone: +1 202 628 2044
Fax: +1 202 628 2042
Email: carl@malamud.com

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

Appendix A. The application/remote-printing Content-Type

(1) MIME type name: application

(2) MIME subtype name: remote-printing

(3) Required parameters: none

(4) Optional parameters: none

(5) Encoding considerations: 7bit preferred

(6) Security considerations: none

(7) Specification:

The "application/remote-printing" content-type contains originator
and recipient information used when generating a cover-sheet. Using
the ABNF notation of RFC822, the syntax for this content is:

<content> ::= <recipient-info> CRLF
<originator-info>
[CRLF <cover-info>]

<recipient-info> ::= "Recipient" ":" <value> CRLF
<address-info>
<originator-info> ::= "Originator" ":" <value> CRLF
<address-info>

<address-info> ::= ["Title" ":" <value> CRLF]
["Department" ":" <value> CRLF]
["Organization" ":" <value> CRLF]
["Mailstop" ":" <value> CRLF]
["Address" ":" <value> CRLF]
["Telephone" ":" <value> CRLF]
"Facsimile" ":" <value> CRLF
["Email" ":" <value> CRLF]
<value> ::= *text
[CRLF LWSP-char <value> ]

<cover-info> ::= *(*text CRLF)

Note that the value of the "Email" field is an RFC822 mailbox
address.

Appendix B. The image/tiff Content-Type

(1) MIME type name: image

(2) MIME subtype name: tiff

(3) Required parameters: none

(4) Optional parameters: none

(5) Encoding considerations: base64

(6) Security considerations: none

(7) Published specification: TIFF class F, as defined in:

Tag Image File Format (TIFF) revision 6.0

Developer's Desk
Aldus Corporation
411 First Ave. South
Suite 200
Seattle, WA 98104
206-622-5500

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