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rfc:rfc1486

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

Rose & Malamud [Page 1] RFC 1486 An Experiment in Remote Printing July 1993

 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.

Rose & Malamud [Page 2] RFC 1486 An Experiment in Remote Printing July 1993

 (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.
 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,
 e.g.,
      +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.,
      remote-printer@0.1.5.2.8.6.9.5.1.4.1.tpc.int
 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
  • .8.6.9.5.1.4.1.tpc.int. IN MX 10 dbc.mtview.ca.us.

Rose & Malamud [Page 3] RFC 1486 An Experiment in Remote Printing July 1993

 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.

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
                             <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)

Rose & Malamud [Page 4] RFC 1486 An Experiment in Remote Printing July 1993

 Note that the value of the "Email" field is an RFC 822 mailbox
 address.

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@0.1.5.2.8.6.9.5.1.4.1.tpc.int
      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"
  1. —— =_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
                    US
      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.
  1. —— =_aaaaaaaaaa0

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

      Here are my comments on your draft.
       ...
  1. —— =_aaaaaaaaaa0–

Rose & Malamud [Page 5] RFC 1486 An Experiment in Remote Printing July 1993

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.,
 remote-printer.Arlington_Hewes/Room_403@0.1.5.2.8.6.9.5.1.4.1.tpc.int
 This mailbox syntax is purposefully restricted in the interests of
 pragmatism.
 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

Rose & Malamud [Page 6] RFC 1486 An Experiment in Remote Printing July 1993

 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
 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@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: 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
 message.

3. The Experiment

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

Rose & Malamud [Page 7] RFC 1486 An Experiment in Remote Printing July 1993

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
 procedures.

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.,
 "9.7.6.tpc.int."

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
 to
  • .5.1.4.1.tpc.int. IN MX 10 dbc.mtview.ca.us.

Rose & Malamud [Page 8] RFC 1486 An Experiment in Remote Printing July 1993

 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
  • .8.6.9.5.1.4.1.tpc.int. 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
  • .6.9.5.1.4.1.tpc.int. 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;
      and,
 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:

Rose & Malamud [Page 9] RFC 1486 An Experiment in Remote Printing July 1993

      tpc-rp-request@aarnet.edu.au
 and ask to subscribe to the
      tpc-rp@aarnet.edu.au
 list.

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
  1. —— =_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
  1. —— =_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>
  1. —— =_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.

Rose & Malamud [Page 10] RFC 1486 An Experiment in Remote Printing July 1993

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
      message.
 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.

Rose & Malamud [Page 11] RFC 1486 An Experiment in Remote Printing July 1993

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

Rose & Malamud [Page 12] RFC 1486 An Experiment in Remote Printing July 1993

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
 recipients.
 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

Rose & Malamud [Page 13] RFC 1486 An Experiment in Remote Printing July 1993

 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
 recipient.

Rose & Malamud [Page 14]

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