Internet Printing Protocol Working Group                     Bob Herriot
INTERNET DRAFT                                         Xerox Corporation
Expires 5 13 August 2001                                      Ira McDonald
                                                          High North Inc
[Target Category: Standards Track]                       5                      13 February 2001

                   Internet Printing Protocol (IPP):
                             IPP URL Scheme
                   <draft-ietf-ipp-url-scheme-01.txt>
                   <draft-ietf-ipp-url-scheme-02.txt>

    Copyright (C) The Internet Society (2001). All Rights Reserved.

Status of this Memo

   This document is an Internet-Draft and is in full conformance with
   all provisions of Section 10 of RFC2026.  Internet-Drafts are working
   documents of the Internet Engineering Task Force (IETF), its areas,
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Abstract

   This document is a product of the Internet Printing Protocol Working
   Group of the Internet Engineering Task Force (IETF).  Comments should
   be submitted to the ipp@pwg.org mailing list.

   This document is intended for use in registering the "ipp" URL scheme
   with IANA and fully conforms to the requirements in [RFC-2717].  This
   document defines the "ipp" URL (Uniform Resource Locator) scheme for
   specifying the location of an IPP Printer, IPP Job, or other IPP
   object (defined in some future version of IPP) which implements the
   IPP/1.1 Model [RFC-2911] and the IPP/1.1 Protocol encoding over HTTP
   [RFC-2910] or any later version of IPP.  The intended usage of the
   "ipp" URL scheme is COMMON.

   The IPP URL scheme defined in this document is based on the ABNF for
   the HTTP URL scheme defined in HTTP/1.1 [RFC-2616], which is derived
   from the URI Generic Syntax [RFC-2396] and further updated by
   [RFC-2732] and [RFC-2373] (for IPv6 addresses in URLs).  An IPP URL
   is transformed into an HTTP URL according to the rules specified in
   section 5 of the IPP/1.1 Protocol [RFC-2910].

                           Table of Contents

1.  Introduction ...............................................       3
2.  Terminology ................................................       4
  2.1.  Conformance Terminology ................................       4
  2.2.  Model Terminology ......................................       4
3.  IPP Model for Printers and Jobs ............................       4
4.  IPP URL Scheme .............................................       5       6
  4.1.  IPP URL Scheme Applicability and Intended Usage ........       5       6
  4.2.  IPP URL Scheme Associated IPP Port .....................       5       6
  4.3.  IPP URL Scheme Associated MIME Type ....................       5       6
  4.4.  IPP URL Scheme Character Encoding ......................       5       6
  4.5.  IPP URL Scheme Syntax in ABNF ..........................       6       7
    4.5.1.  IPP URL Examples ...................................       7       8
    4.5.2.  IPP URL Comparisons ................................       8       9
5.  Conformance Requirements ...................................       9      10
  5.1.  Conformance Requirements for IPP Clients ...............       9      10
  5.2.  Conformance Requirements for IPP Printers ..............       9      10
6.  IANA Considerations ........................................      10      11
7.  Internationalization Considerations ........................      10      11
8.  Security Considerations ....................................      10      11
9.  References .................................................      11      12
10.  Acknowledgments ...........................................      12      13
11.  Authors' Addresses ........................................      13      14
12.  Appendix X - Change History ...............................      13      14
13.  Full Copyright Statement ..................................      14      15

1.  Introduction

   See section 1 'Introduction' in [RFC-2911] for a full description of
   the IPP document set and overview information about IPP.

   The open issues in this document each begin 'ISSUE_n:'.

   This document is a product of the Internet Printing Protocol Working
   Group of the Internet Engineering Task Force (IETF).  Comments should
   be submitted to the ipp@pwg.org mailing list.

   This document is intended for use in registering the "ipp" URL scheme
   with IANA and fully conforms to the requirements in [RFC-2717].  This
   document defines the "ipp" URL (Uniform Resource Locator) scheme for
   specifying the location of an IPP Printer, IPP Job, or other IPP
   object (defined in some future version of IPP) which implements the
   IPP/1.1 Model [RFC-2911] and the IPP/1.1 Protocol encoding over HTTP
   [RFC-2910] or any later version of IPP.  The intended usage of the
   "ipp" URL scheme is COMMON.

   This document defines:
   - IPP URL scheme applicability and intended usage;
   - IPP URL scheme associated port (i.e., well-known port 631);
   - IPP URL scheme associated MIME type (i.e., "application/ipp");
   - IPP URL scheme syntax in ABNF [RFC-2234];
   - IPP URL scheme character encoding;
   - IPP URL scheme IANA, internationalization, and security
     considerations.

   This document is laid out as follows:
   - Section 2 is the terminology used throughout the document.

   - Section 3 provides references to the IPP Printer and IPP Job object
     model.

   - Section 4 specifies IPP URL scheme.

   - Section 5 specifies the conformance requirements for IPP Clients
     and IPP Printers that claim conformance to this document.

   - Section 6, 7, and 8 specify IANA, internationalization, and
     security considerations.

   - Sections 9, 10, 11, 12, and 13 list references, acknowledgements,
     authors' addresses, change history, and full IETF copyright
     statement.

2.  Terminology

   This specification document uses the terminology defined in this
   section.

   2.1.  Conformance Terminology

   The uppercase terms "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL
   NOT" "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in
   this document are to be interpreted as described in [RFC-2119].
   These terms are used to specify conformance requirements for all
   implementations of this specification.

   2.2.  Model Terminology

   See section 12.2 'Model Terminology' in [RFC-2911].

3.  IPP Model for Printers and Jobs

   See section 2 'IPP Objects', section 2.1 'Printer Object', and
   section 2.2 'Job Object' in [RFC-2911] for a full description of the
   IPP object model and terminology.

   In this document, "IPP Client" means the software (on some hardware
   platform) that submits, monitors, and/or manages print jobs via
   IPP/1.1 [RFC-2910] [RFC-2911], or any later version of IPP to a
   spooler, gateway, or actual printing device.

   In this document, "IPP Printer object" means the software (on some
   hardware platform) that receives print jobs and/or printer/job
   operations via IPP/1.1 [RFC-2910] [RFC-2911], or any later version of
   IPP from an "IPP Client".

   In this document, "IPP Printer" is a synonym for "IPP Printer
   object".

   In this document, "IPP Job object" means the set of attributes and
   documents for one print job on an "IPP Printer".

   In this document, "IPP Job" is a synonym for "IPP Job object".

   In this document, "IPP URL" means a URL with the "ipp" scheme.

   Note:  In this document, "IPP URL" is a synonym for "ipp_URL" (in
   section 4 'IPP URL Scheme' of this document) and "ipp-URL" (in
   section 5 'IPP URL Scheme' of [RFC-2910]).

4.  IPP URL Scheme

   4.1.  IPP URL Scheme Applicability and Intended Usage

   This document is intended for use in registering the "ipp" URL scheme
   with IANA and fully conforms to the requirements in [RFC-2717].  This
   document defines the "ipp" URL (Uniform Resource Locator) scheme for
   specifying the location of an IPP Printer, IPP Job, or other IPP
   object (defined in some future version of IPP) which implements the
   IPP/1.1 Model [RFC-2911] and the IPP/1.1 Protocol encoding over HTTP
   [RFC-2910] or any later version of IPP.  The intended usage of the
   "ipp" URL scheme is COMMON.

   4.2.  IPP URL Scheme Associated IPP Port

   All IPP URLs which do NOT explicitly specify a port MUST be used over
   IANA-assigned well-known port 631 for the IPP protocol described in
   [RFC-2910].

   See:  IANA Port Numbers Registry [IANA-PORTREG].  registration with
   IANA.

   4.3.  IPP URL Scheme Associated MIME Type

   All IPP protocol operations (requests and responses) MUST be conveyed
   in an "application/ipp" MIME media type as registered in
   [IANA-MIMEREG].  IPP URLs MUST refer to IPP Printers which support
   this "application/ipp" MIME media type.

   See:  IANA MIME Media Types Registry [IANA-MIMEREG].

   4.4.  IPP URL Scheme Character Encoding

   The IPP URL scheme defined in this document is based on the ABNF for
   the HTTP URL scheme defined in HTTP/1.1 [RFC-2616], which is derived
   from the URI Generic Syntax [RFC-2396] and further updated by
   [RFC-2732] and [RFC-2373] (for IPv6 addresses in URLs).  The IPP URL
   scheme is case-insensitive in the host name or host address part;
   however the path part is case-sensitive, as in [RFC-2396].
   Codepoints outside [US-ASCII] MUST be hex escaped by the mechanism
   specified in [RFC-2396].

   4.5.  IPP URL Scheme Syntax in ABNF

   Note:  In this document, "IPP URL" is a synonym for "ipp_URL" (in
   section 4 'IPP URL Scheme' of this document) and "ipp-URL" (in
   section 5 'IPP URL Scheme' of [RFC-2910]).

   This document is intended for use in registering the "ipp" URL scheme
   with IANA and fully conforms to the requirements in [RFC-2717].  This
   document defines the "ipp" URL (Uniform Resource Locator) scheme for
   specifying the location of an IPP Printer, IPP Job, or other IPP
   object (defined in some future version of IPP) which implements the
   IPP/1.1 Model [RFC-2911] and the IPP/1.1 Protocol encoding over HTTP
   [RFC-2910] or any later version of IPP.  The intended usage of the
   "ipp" URL scheme is COMMON.

   The IPP protocol places a limit of 1023 octets (NOT characters) on
   the length of a URI in (see section 4.1.5 'uri' in [RFC-2911].  An IPP Printer
   implementation MUST be able to handle the URI of any resource that it
   supports. [RFC-2911]).  An IPP
   Printer MUST return 'client-error-request-value-too-long' (see
   section 13.1.4.10 in [RFC-2911]) when a URI received in a request
   (e.g., in the "printer-uri" attribute) is too long.

      Note:  IPP Printers ought to be cautious about depending on URI
      lengths above 255 bytes, because some older client or proxy
      implementations might not properly support these lengths.

   IPP URLs MUST be represented in absolute form.  Absolute URLs always
   begin with a scheme name followed by a colon.  For definitive
   information on URL syntax and semantics, see "Uniform Resource
   Identifiers (URI): Generic Syntax and Semantics" [RFC-2396].  This
   specification adopts the definitions of "URI-reference",
   "absoluteURI", "relativeURI", "port", "host","abs_path", "rel_path",
   and "authority" from [RFC-2396], as updated by [RFC-2732] and
   [RFC-2373] (for IPv6 addresses in URLs).

   The IPP URL scheme syntax in ABNF is as follows:

   ipp_URL = "http:" "ipp:" "//" host [ ":" port ] [ abs_path [ "?" query ]]

   If the port is empty or not given, port 631 is assumed.  The
   semantics are that the identified resource (see section 5.1.2 of
   [RFC-2616]) is located at the IPP Printer or IPP Job listening for
   HTTP connections on that port of that host, and the Request-URI for
   the identified resource is 'abs_path'.

   Note:  The use of IP addresses in URLs SHOULD be avoided whenever
   possible (see [RFC-1900]).

   If the 'abs_path' is not present in the URL, it MUST be given as "/"
   when used as a Request-URI for a resource (see section 5.1.2 of
   [RFC-2616]).  If a proxy receives a host name which is not a fully
   qualified domain name, it MAY add its domain to the host name it
   received.  If a proxy receives a fully qualified domain name, the
   proxy MUST NOT change the host name.

   4.5.1.  IPP URL Examples

   The following are examples of valid IPP URLs for IPP Printers:

       ipp://abc.com
       ipp://abc.com/printer
       ipp://abc.com/tiger
       ipp://abc.com/printers/tiger
       ipp://abc.com/printers/fox
       ipp://abc.com/printers/tiger/bob
       ipp://abc.com/printers/tiger/ira
       ipp://printer.abc.com
       ipp://printers.abc.com/tiger
       ipp://printers.abc.com/tiger/bob
       ipp://printers.abc.com/tiger/ira

   Each of the above URLs are legitimate URLs for IPP Printers and each
   references a logically different IPP Printer, even though some of the
   IPP Printers may share the same hardware.  The last part of the path
   'bob' or 'ira' may represent two different hardware devices where
   'tiger' represents some grouping of IPP Printers (e.g., a
   load-balancing spooler) or the two names may represent separate human
   recipients ('bob' and 'ira') on the same hardware device (e.g., a
   printer supporting two job queues).  In either case both 'bob' and
   'ira' behave as different IPP Printers.

   The following are examples of IPP URLs with (optional) ports and
   paths:

       ipp://abc.com
       ipp://abc.com/~smith/printer
       ipp://abc.com:631/~smith/printer

   The first and second IPP URLs above MUST be resolved to port 631
   (IANA assigned well-known port for IPP).  The second and third IPP
   URLs above are equivalent (see section 4.5.2 below).

   Note:  The use of IP addresses in URLs SHOULD be avoided whenever
   possible (see [RFC-1900]).

   The following literal IPv4 addresses:

       192.9.5.5                           ; IPv4 address in IPv4 style
       186.7.8.9                           ; IPv4 address in IPv4 style

   are represented in the following example IPP URLs:

       ipp://192.9.5.5/prt1
       ipp://186.7.8.9/printers/tiger/bob

   The following literal IPv6 addresses (conformant to [RFC-2373]):

       ::192.9.5.5                         ; IPv4 address in IPv6 style
       ::FFFF:129.144.52.38                ; IPv4 address in IPv6 style
       2010:836B:4179::836B:4179           ; IPv6 address per RFC 2373

   are represented in the following example IPP URLs:

       ipp://[::192.9.5.5]/prt1
       ipp://[::FFFF:129.144.52.38]:631/printers/tiger
       ipp://[2010:836B:4179::836B:4179]/printers/tiger/bob

   4.5.2.  IPP URL Comparisons

   When comparing two IPP URLs to decide if they match or not, an IPP
   Client SHOULD use a case-sensitive octet-by-octet comparison of the
   entire URLs, with these exceptions:

   - A port that is empty or not given is equivalent to the well-known
     port for that IPP URL (port 631);

   - Comparisons of host names MUST be case-insensitive;

   - Comparisons of scheme names MUST be case-insensitive;

   - An empty 'abs_path' is equivalent to an 'abs_path' of "/".

   Characters other than those in the "reserved" and "unsafe" sets (see
   [RFC-2396] and [RFC-2732]) are equivalent to their ""%" HEX HEX"
   encoding.

   For example, the following three URIs are equivalent:

       ipp://abc.com:631/~smith/printer
       ipp://ABC.com/%7Esmith/printer
       ipp://ABC.com:/%7esmith/printer

5.  Conformance Requirements

   5.1.  Conformance Requirements for IPP Clients

   IPP Clients that conform to this specification:

   a) MUST send IPP URLs (e.g., in the "printer-uri" operation attribute
      in 'Print-Job') that conform to the ABNF specified in section 4.5
      of this document;

   b) MUST send IPP operations via the port specified in the IPP URL (if
      present) or otherwise via IANA assigned well-known port 631;

   c) MUST convert IPP URLs to their corresponding HTTP URL forms
      according to the rules in section 5 'IPP URL Scheme' in
      [RFC-2910];

   d) SHOULD interoperate with IPP/1.0 Printers according to the rules
      in section 9 'Interoperability with IPP/1.0 Implementations' and
      section 9.2 'Security and URL Schemes' in [RFC-2910].

   5.2.  Conformance Requirements for IPP Printers

   IPP Printers that conform to this specification:

   a) SHOULD reject received IPP URLs in "application/ipp" request
      bodies (e.g., in the "printer-uri" attribute in a 'Print-Job'
      request) that do not conform to the ABNF for IPP URLs specified in
      section 4.5 of this document;

   b) SHOULD return IPP URLs in "application/ipp" response bodies (e.g.,
      in the "job-uri" attribute in a 'Print-Job' response) that do
      conform to the ABNF for IPP URLs specified in section 4.5 of this
      document;

   c) MUST listen for IPP operations on IANA-assigned well-known port
      631, unless explicitly configured by system administrators or site
      policies;

   d) SHOULD NOT listen for IPP operations on any other port, unless
      explicitly configured by system administrators or site policies;

   e) SHOULD interoperate with IPP/1.0 Clients according to the rules in
      section 9 'Interoperability with IPP/1.0 Implementations' and
      section 9.2 'Security and URL Schemes' in [RFC-2910].

6.  IANA Considerations

   This document is intended for use in registering the "ipp" URL scheme
   with IANA and fully conforms to the requirements in [RFC-2717].  This
   document defines the "ipp" URL (Uniform Resource Locator) scheme for
   specifying the location of an IPP Printer, IPP Job, or other IPP
   object (defined in some future version of IPP) which implements the
   IPP/1.1 Model [RFC-2911] and the IPP/1.1 Protocol encoding over HTTP
   [RFC-2910] or any later version of IPP.  The intended usage of the
   "ipp" URL scheme is COMMON.

   This IPP URL Scheme specification does not introduce any additional
   IANA considerations, beyond those described in [RFC-2910] and
   [RFC-2911].

   See:  Section 6 'IANA Considerations' in [RFC-2910]
   See:  Section 6 'IANA Considerations' in [RFC-2911].

7.  Internationalization Considerations

   This IPP URL Scheme specification does not introduce any additional
   internationalization considerations, beyond those described in
   [RFC-2910] and [RFC-2911].

   See:  Section 7 'Internationalization Considerations' in [RFC-2910].
   See:  Section 7 'Internationalization Considerations' in [RFC-2911].

8.  Security Considerations

   This IPP URL Scheme specification does not introduce any additional
   security considerations, beyond those described in [RFC-2910] and
   [RFC-2911].

   See:  Section 8 'Security Considerations' in [RFC-2910].
   See:  Section 8 'Security Considerations' in [RFC-2911].

9.  References

   See:  Section 10 'References' in [RFC-2910].
   See:  Section 9 'References' in [RFC-2911].

   [IANA-CHARREG] IANA Charset Registry.
   ftp://ftp.isi.edu/in-notes/iana/assignments/character-sets

   [IANA-MIMEREG] IANA MIME Media Types Registry.
   ftp://ftp.isi.edu/in-notes/iana/assignments/media-types/...

   [IANA-PORTREG] IANA Port Numbers Registry.
   ftp://ftp.isi.edu/in-notes/iana/assignments/port-numbers

   [NET-SSL3] Netscape.  The SSL Protocol, Version 3 (text version
   3.02), November 1996.

   [RFC-1759] R. Smith, F. Wright, T. Hastings, S. Zilles,
   J. Gyllenskog.  Printer MIB, RFC 1759, March 1995.

   [RFC-1900] B. Carpenter, Y. Rekhter.  Renumbering Needs Work, RFC
   1900, February 1996.

   [RFC-2046] N. Freed, N. Borenstein.  MIME Part Two: Media Types, RFC
   2046, November 1996.

   [RFC-2048] N. Freed, J. Klensin, J. Postel.  MIME Part
   Four: Registration Procedures, RFC 2048, November 1996.

   [RFC-2234] D. Crocker, P. Overell.  Augmented BNF for Syntax
   Specifications: ABNF, RFC 2234, November 1997.

   [RFC-2373] R. Hinden, S. Deering.  IP Version 6 Addressing
   Architecture, RFC 2373, July 1998.

   [RFC-2396] T. Berners-Lee, R. Fielding, L. Masinter.  Uniform
   Resource Identifiers (URI): Generic Syntax, RFC 2396, August 1998.

   [RFC-2246] T. Dierks, C. Allen.  The TLS Protocol Version, RFC 2246,
   January 1999.

   [RFC-2277] H. Alvestrand.  IETF Policy on Character Sets and
   Languages, RFC 2277, January 1998.

   [RFC-2279] F. Yergeau.  UTF-8, a Transformation Format of ISO 10646,
   RFC 2279, January 1998.

   [RFC-2565] R. Herriot, S. Butler, P. Moore, R. Turner.  IPP/1.0
   Encoding and Transport, RFC 2565, April 1999 (Experimental).

   [RFC-2566] R. deBry, T. Hastings, R. Herriot, S. Isaacson, P. Powell.
   IPP/1.0 Model and Semantics, RFC 2566, April 1999 (Experimental).

   [RFC-2579] K. McCloghrie, D. Perkins, J. Schoenwaelder.  Textual
   Conventions for SMIv2, RFC 2579, April 1999.

   [RFC-2616] R. Fielding, J. Gettys, J. Mogul, H. Frystyk, L. Masinter,
   P. Leach, T. Berners-Lee.  Hypertext Transfer Protocol -- HTTP/1.1,
   RFC 2616, June 1999.

   [RFC-2617] J. Franks, P. Hallam-Baker, J. Hostetler, S. Lawrence,
   P. Leach, A. Luotonen, L. Stewart.  HTTP Authentication:  Basic and
   Digest Access Authentication, RFC 2617, June 1999.

   [RFC-2717] R. Petke, I. King.  Registration Procedures for URL Scheme
   Names, RFC 2717, November 1999.

   [RFC-2718] L. Masinter, H. Alvestrand, D. Zigmond, R. Petke.
   Guidelines for new URL Scheme Names, RFC 2718, November 1999.

   [RFC-2732] R. Hinden,B. Carpenter, L. Masinter.  Format for Literal
   IPv6 Addresses in URL's, RFC 2732, December 1999.

   [RFC-2910] R. Herriot, S. Butler, P. Moore, R. Turner, J. Wenn.
   IPP/1.1 Encoding and Transport, RFC 2910, September 2000.

   [RFC-2911] T. Hastings, R. Herriot, R. deBry, S. Isaacson, P. Powell.
   IPP/1.1 Model and Semantics, RFC 2911, September 2000.

   [RFC-2978] N. Freed, J. Postel.  IANA Charset Registration
   Procedures, RFC 2978, October 2000.

   [RFC-3066] H. Alvestrand.  Tags for the Identification of Languages,
   RFC 3066, January 2001.

   [US-ASCII] Coded Character Set -- 7-bit American Standard Code for
   Information Interchange, ANSI X3.4-1986.

10.  Acknowledgments

   This document is a product of the Internet Printing Protocol Working
   Group of the Internet Engineering Task Force (IETF).  Comments should
   be submitted to the ipp@pwg.org mailing list.

   Thanks to Pat Fleming (IBM), Tom Hastings (Xerox), Harry Lewis (IBM),
   and Hugo Parra (Novell).

   Section 5 'IPP URL Scheme' in IPP/1.1 Encoding and Transport
   [RFC-2910] was the primary input to this IPP URL Scheme
   specification.

11.  Authors' Addresses

   Robert Herriot
   Xerox Corporation
   3400 Hill View Ave, Building 1
   Palo Alto, CA 94304

   Phone: +1 650-813-7696
   Fax:   +1 650-813-6860
   Email: robert.herriot@pahv.xerox.com

   Ira McDonald
   High North Inc
   221 Ridge Ave
   Grand Marais, MI  49839

   Phone: +1 906-494-2434
   Email: imcdonald@crt.xerox.com
   Email: imcdonald@sharplabs.com

12.  Appendix X - Change History

   [To be deleted before RFC publication]

   13 February 2001 - draft-ietf-ipp-url-scheme-02.txt
   - revised section 3 'IPP Model for Printers and Jobs' and section 4.5
     'IPP URL Scheme Syntax in ABNF' to add notes stating that "IPP URL"
     (in this document) is a synonym for "ipp-URL" in [RFC-2910], per
     request of Bob Herriot;
   - revised section 4.5 'IPP URL Scheme Syntax in ABNF' to correct typo
     that showed "http:" rather than "ipp:" in the one-line ABNF, per
     request of Tom Hastings;
   - revised section 4.5.1 'IPP URL Examples' to add a note discouraging
     the use of literal IP addresses in URLs, per [RFC-2616] and
     [RFC-1900];

   5 February 2001 - draft-ietf-ipp-url-scheme-01.txt
   - revised section 4.1 'IPP URL Applicability and Intended Usage' to
     clarify that a given IPP URL MAY identify an IPP Printer object or
     an IPP Job object, per request of Tom Hastings;
   - revised section 4.5 'IPP URL Scheme Syntax in ABNF' to define IPP
     URLs consistently with section 3.2.2 'http URL' of HTTP/1.1
     [RFC-2616], per request of Tom Hastings;
   - revised section 4.5 'IPP URL Scheme Syntax in ABNF' to clarify that
     IPP URLs may reference IPP Printer objects, IPP Job objects, or
     (possibly other future) IPP objects, per request of Bob Herriot;
   - added section 4.5.1 'IPP URL Examples' to supply meaningful
     examples of IPP URLs with host names, IPv4 addresses, and IPv6
     addresses, per request of Tom Hastings;
   - added section 4.5.2 'IPP URL Comparisons' to define IPP URL
     comparisons consistently with section 3.3 'URI Comparison' of
     HTTP/1.1 [RFC-2616], per request of Tom Hastings;
   - revised section 5.1 'Conformance Requirements for IPP Clients' to
     clarify that an IPP Client MUST convert IPP URLs to their
     corresponding HTTP URL forms according to section 5 'IPP URL
     Scheme' in [RFC-2910], per request of Tom Hastings and Bob Herriot;
   - revised section 5.1 'Conformance Requirements for IPP Clients' and
     section 5.2 'Conformance Requirements for IPP Printers' to clarify
     that IPP Clients and IPP Printers SHOULD interoperate with IPP/1.0
     systems according to section 9 'Interoperability with IPP/1.0
     Implementations' in [RFC-2910], per request of Carl Kugler;
   - revised section 5.2 'Conformance Requirements for IPP Printers' to
     clarify that an IPP Printer MUST listen on (IANA assigned
     well-known) port 631, unless explicitly configured, per request of
     Michael Sweet;
   - revised section 5.2 'Conformance Requirements for IPP Printers' to
     clarify that an IPP Printer SHOULD NOT listen on ports other than
     (IANA assigned well-known) port 631, unless explicitly configured,
     per request of Don Wright;
   - revised section 6 'IANA Considerations' to clarify that the sole
     purpose of the entire document is IANA registration of the "ipp"
     URL scheme;
   - deleted Appendix A 'Registration of IPP Port' as unnecessary (port
     is already registered);
   - deleted Appendix B 'Registration of MIME "application/ipp" as
     unnecessary (MIME registry has recently caught up to RFC 2910);

   11 January 2001 - draft-ietf-ipp-url-scheme-00.txt
   - initial version - simple 'ipp:' "ipp" URL scheme without parameters or
     query part (consistent with existing and IPP/1.1 implementations);
   - added Appendix A 'Registration of IPP Port' (placeholder) for
     updated IANA registration of port 631 with references to IPP/1.1;
   - added Appendix B 'Registration of MIME "application/ipp"' with
     updated IANA registration for IPP MIME type with references to both
     IPP/1.0 and IPP/1.1;

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