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RFC 1486 - An Experiment in Remote Printing

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Network Working Group                                            M. Rose
Request for Comments: 1486                  Dover Beach Consulting, Inc.
                                                              C. Malamud
                                           Internet Multicasting Service
                                                               July 1993

                    An Experiment in Remote Printing

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 "IAB Official Protocol Standards" for the
   standardization state and status of this protocol.  Distribution of
   this memo is unlimited.

Table of Contents

   1. Introduction ..........................................    1
   1.1 The Advantage of a General-Purpose Infrastructure.....    2
   2. Procedure .............................................    2
   2.1 Naming, Addressing, and Routing ......................    3
   2.2 The application/remote-printing Content-Type .........    4
   2.3 Usage Example ........................................    5
   2.4 Remote Printing without MIME .........................    6
   3. The Experiment ........................................    7
   3.1 Infrastructure .......................................    8
   3.1.1 Zones ..............................................    8
   3.1.2 MX records .........................................    8
   3.2 Accounting and Privacy ...............................    9
   3.3 Mailing list .........................................    9
   3.4 Prototype Implementation .............................   10
   4. Future Issues .........................................   11
   5. Security Considerations ...............................   11
   6. Acknowledgements ......................................   11
   7. References ............................................   11
   8. Authors' Addresses.....................................   12
   A.  The image/tiff Content-Type ..........................   13
   B.  Uniform Addressing ...................................   13

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.  Furthermore, it describes an experiment in remote printing.

1.1.  The Advantage of a General-Purpose Infrastructure

   The experiment in remote printing is about "outreach"; specifically,
   integrating the e-mail and facsimile communities.  By providing easy
   access to remote printing recipients, enterprise-wide access is
   enhanced, regardless of kind of institution (e.g., commercial,
   educational, or government), or the size of institution (e.g.,
   global, regional, or local).  This approach at outreach allows an
   organization to make it easier for the "outside world" to communicate
   with the personnel in the organization who are users of facsimile but
   not e-mail; e.g., the sales person, the university registrar, or the
   (elected) official.  The ease in which the Internet mail
   infrastructure can be used to provide this facility is (yet) another
   example of the power of a general-purpose infrastructure.

2.  Procedure

   When information is to be remotely printed, the user application
   constructs an RFC 822 [1] message, containing a "Message-ID" field
   along with a "multipart/mixed" content [2] having two parts, the
   first being a "application/remote-printing" content-type, and the
   second being an arbitrary content-type corresponding to the
   information to be printed.  The message is then sent to the remote
   printer server's electronic mail address.

   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 A), 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

   (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.

   When the remote printer server finishes its processing, a message is
   returned to the originator, indicating either success or failure.

2.1.  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,

        +1 415 968 2510

   where "+1" indicates the IDDD country code, and the remaining string
   is a telephone number within that country.  This number is used to
   construct the address of a remote printer server, which forms the
   recipient address for the message, e.g.,


   That is, the local-part of the remote printer server's address is
   ALWAYS "remote-printer", 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 message is routed in exactly the same fashion as all other
   electronic mail, i.e., using the MX algorithm [3].  Since a remote
   printer server might be able to access many printers, the wildcarding
   facilities of the DNS [4,5] 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

        *.    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

   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.

2.2.  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

   The "application/remote-printing" content-type contains originator
   and recipient information used when generating a cover sheet.  Using
   the ABNF notation of RFC 822, the syntax for this content is:

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

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

        <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 RFC 822 mailbox

2.3.  Usage Example

   Suppose someone wished to send the author some comments on this memo
   using this facility.  The message constructed might look like this:

        To: remote-printer@
        From: "John Q. Public" <jpublic@tpd.org>
        Date: Sun, 11 Apr 1993 20:34:13 -0800
        Subject: Comments on "An Experiment in Remote Printing"
        Message-ID: <19930411203413000.456@tpd.org>
        MIME-Version: 1.0
        Content-Type: multipart/mixed;
                boundary="----- =_aaaaaaaaaa0"

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

        Recipient:    Marshall Rose
        Title:        Principal
        Organization: Dover Beach Consulting, Inc.
        Address:      420 Whisman Court
                      Mountain View, CA  94043-2186
        Telephone:    +1 415 968 1052
        Facsimile:    +1 415 968 2510

        Originator:   John Q. Public
        Organization: The Public Domain
        Telephone:    +1 801 555 1234
        Facsimile:    +1 801 555 6789
        EMail:        "John Q. Public" <jpublic@tpd.org>

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

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

        Here are my comments on your draft.


        ------- =_aaaaaaaaaa0--

2.4.  Remote Printing without MIME

   If the originator's user agent doesn't support MIME, (e.g., the
   originator accesses the Internet mail infrastructure via a gateway in
   another mail dominion), then it is still possible for remote printing
   to occur, albeit in a more limited fashion.  Specifically, because a
   "application/remote-printing" content is not present, cover sheet
   information must be derived from some other source; and, the message
   body will be treated as a "text/plain" content.

   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, an alternative syntax is used for
   recipient addressing, in which the local-part of the remote printer
   server's address consists of "remote-printer" followed by an RFC 822
   atom, e.g.,


   This mailbox syntax is purposefully restricted in the interests of

   The atom following "remote-printer" is considered an opaque string
   for use in recipient identification when generating a cover sheet.

   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)>
              / "!" / "#" / "$" / "%" / "&" / "'" / "*" / "+"
              / "-" / "/" / "=" / "?" / "^" / "_" / "`" / "{"
              / "|" / "}" / "~"

   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


   used in the example above might appear on the cover sheet as

        To: Arlington Hewes
            Room 403

   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.

   Note that by using the alternative syntax for recipient addressing,
   it is completely legal to send non- textual messages in which the
   cover sheet information is automatically derived -- simply by
   including "MIME-Version:" and "Content-Type:" headers in the message,
   but omitting the initial "application/remote-printing" content, e.g.,

To: remote-printer.Arlington_Hewes/Room_403@
cc: Marshall Rose <mrose@dbc.mtview.ca.us>
From: Carl Malamud <carl@malamud.com>
Date: Sun, 18 Jul 1993 09:14:13 -0500
Subject: proposal for enhancement
Message-ID: <19930718141413000.123@malamud.com>
MIME-Version: 1.0
Content-Type: application/postcript


   Note that by using the alternative syntax for recipient addressing,
   remote printing and e-mail recipients can be identified in the same

3.  The Experiment

   In order to gain experience with this style of remote printing, an
   experiment is underway.

3.1.  Infrastructure

   The domain "tpc.int." is being populated in order to provide the MX-
   based infrastructure for routing to a remote printer server.  In
   order to facilitate distributed operations, this domain is divided
   into a zone for each IDDD country code.  Sites participating in the
   experiment contact the appropriate zone administrator in order to be
   listed, by examining the SOA resource record associated with the
   zone.  For example, a site in the Netherlands (IDDD country code 31)
   would contact the zone administrator for the domain "1.3.tpc.int." in
   order to be listed, e.g.,

        % dig 1.3.tpc.int. soa

   Each zone administrator has a simple set of procedures for listing a
   participant.  For example, in the US (IDDD country code 1),
   participating sites send an "exchange file" to the administrator,
   which indicates the prefixes that the site wishes to list.  The zone
   administrator for the domain "1.tpc.int." merges the exchange files
   from all participating sites to create a zone for each area code.
   These zones are then replicated using the normal DNS zone transfer

3.1.1.  Zones

   It should be noted that zones under "tpc.int" are created on the
   basis of IDDD country codes and area codes; they are not created for
   each subdomain.  For example, in the US and Canada (IDDD country code
   1), no more than one zone is allocated for each area code.  In
   contrast, for countries with a smaller numbering plan, only a single
   zone, for the whole country would be allocated.  For example, if Fiji
   (IDDD country code 679), were to join the experiment, then it is
   likely that a single zone would be added to the DNS, i.e.,

3.1.2.  MX records

   The MX records present in a zone can have an arbitrary level of
   precision.  For example, the North American Numbering Plan (IDDD
   country code 1) is structured by a 3-digit area code, followed by a
   3-digit exchange prefix, followed by a 4-digit station number.  As
   such, one might expect that MX records in this zone would be similar

        *.          IN MX 10 dbc.mtview.ca.us.

   which accessed any printer with a telephone number prefix of

        +1 415

   (i.e., allowing access to any printer in area code 415), or might be
   similar to

        *.    IN MX 10 dbc.mtview.ca.us.

   (i.e., allowing access to any printer in area code 415, exchange
   prefix 968).

   However, the level of precision is arbitrary.  For example, if all of
   the printers in an organization had a telephone number prefix of

        +1 415 96

   then an MX record such as

        *.    IN MX 10 dbc.mtview.ca.us.

   could be used.

3.2.  Accounting and Privacy

   There is no accounting nor settlement in the experiment; however,
   participating sites may implement access control to prevent abuse.
   Records may be kept for auditing purposes; however, the privacy of a
   participant's printing should be honored.  As such, any auditing
   should contain at most this information:

   o    the date the message was received;

   o    the "From" and "Message-ID" fields;

   o    the size of the body;

   o    the identity (telephone number) of the printer;

   o    any telephony-related information, such as call duration;

   o    any G3-related information, such recipient ID.

3.3.  Mailing list

   There is a mailing list for the experiment.  Interested readers
   should send a note to:


   and ask to subscribe to the



3.4.  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;

        Content-Type: application/octet-stream; type="tar";
        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";
        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

4.  Future Issues

   The experiment in remote printing described herein does not address
   several issues, 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

   Initially, the experiment will not address these issues.  However,
   subsequent work might consider these issues in detail.

5.  Security Considerations

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

6.  Acknowledgements

   Carl Malamud of the Internet Multicasting Service provided
   substantive comments on the design of the experiment.  Douglas Comer
   of Purdue, Daniel Karrenberg of RIPE, Sam Leffler of SGI, Paul
   Mockapetris of ARPA, also provided comments.

7.  References

   [1] Crocker, D., "Standard for the Format of ARPA Internet Text
       Messages", STD 11, RFC 822, UDEL, August, 1982.

   [2] Borenstein, N., and N. Freed, "MIME: Mechanisms for Specifying
       and Describing the Format of Internet Message Bodies", RFC 1341,
       Bellcore, Innosoft, June 1992.

   [3] Partridge, C., "Mail Routing and the Domain System", RFC 974,
       CSNET CIC BBN, August 1982.

   [4] Mockapetris, P., "Domain Names -- Concepts and Facilities", STD
       13, RFC 1034, USC/Information Sciences Institute, November 1987.

   [5] Mockapetris, P., "Domain Names -- Implementation and
       Specification", STD 13, RFC 1035, USC/Information Sciences
       Institute, November 1987.

8.  Authors' Addresses

   Marshall T. Rose
   Dover Beach Consulting, Inc.
   420 Whisman Court
   Mountain View, CA  94043-2186

   Phone: +1 415 968 1052
   Fax:   +1 415 968 2510
   EMail: mrose@dbc.mtview.ca.us

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

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

Appendix A.  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

Appendix B.  Uniform Addressing

   A user may choose to include several recipients in a message, one or
   more of which may be recipients reached via remote printing.
   However, the message format accepted by a remote printer server
   contains only a single recipient.

   There are three solutions to this problem: first, during composition,
   a "smart" user agent can determine that one or more remote printing
   recipients are present, and submit the appropriate messages.  This
   has the disadvantage that the submission for the e-mail recipients
   does not contain any information about the remote-printing

   A second solution is to use the alternative syntax for recipient
   addressing described in Section 2.4 -- however, this minimizes useful
   information available when constructing the cover sheet.

   A third solution is for a site participating as a client to offer a
   remote printing recipient exploder server to its users.  Each remote
   printing recipient is assigned a mailbox relative to the exploder,
   and, as such, appears as an "ordinary" e-mail address.  Using this
   strategy, the user agent has no knowledge of which recipients are
   accessible via e-mail or remote-printing -- the user simply specifies
   a collection of mailbox recipients.  Those recipients which are
   accessible via remote-printing are automatically routed to the
   exploder.  For each recipient in the envelope, a local database is

   consulted to retrieve addressing information for the recipient, and a
   message is submitted to the appropriate remote printer server.

For example, if the original message submitted was:

        To: mrose@rpexplode.tpd.org
        cc: Arlington Hewes <tpcadmin@dbc.mtview.ca.us>
        From: "John Q. Public" <jpublic@tpd.org>
        Date: Sun, 11 Apr 1993 20:34:12 -0800
        Subject: Comments on "An Experiment in Remote Printing"
        Message-ID: <19930411203412000.123@tpd.org>
        MIME-Version: 1.0
        Content-Type: text/plain; charset=us-ascii

        Here are my comments on your draft.

   then the first recipient, "mrose@rpexplode.tpd.org", would be routed
   to an remote printing exploder, which would submit the message shown
   in the example in Section 2.3.  The second recipient,
   "tpcadmin@dbc.mtview.ca.us", would receive the message shown here.
   Note that a reply by this recipient could include the remote printing


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