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.
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
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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) RFC 822 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."
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RFC 1528 Remote Printing -- Technical Procedures October 1993
Note that the mailbox syntax is purposefully restricted in the interests of pragmatism. To paraphrase RFC 822, an atom is defined as:
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 RFC 822 message, containing a "Message-ID" field.
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RFC 1528 Remote Printing -- Technical Procedures October 1993
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
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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
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
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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"
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.
