Rationale for the Structure of the Model and Protocol for the Internet Printing Protocol
RFC 2568

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Network Working Group                                          S. Zilles
Request for Comments: 2568                            Adobe Systems Inc.
Category: Experimental                                        April 1999

         Rationale for the Structure of the Model and Protocol
                   for the Internet Printing Protocol

Status of this Memo

   This memo defines an Experimental Protocol for the Internet
   community.  It does not specify an Internet standard of any kind.
   Discussion and suggestions for improvement are requested.
   Distribution of this memo is unlimited.

Copyright Notice

   Copyright (C) The Internet Society (1999).  All Rights Reserved.

IESG Note

   This document defines an Experimental protocol for the Internet
   community.  The IESG expects that a revised version of this protocol
   will be published as Proposed Standard protocol.  The Proposed
   Standard, when published, is expected to change from the protocol
   defined in this memo.  In particular, it is expected that the
   standards-track version of the protocol will incorporate strong
   authentication and privacy features, and that an "ipp:" URL type will
   be defined which supports those security measures.  Other changes to
   the protocol are also possible.  Implementors are warned that future
   versions of this protocol may not interoperate with the version of
   IPP defined in this document, or if they do interoperate, that some
   protocol features may not be available.

   The IESG encourages experimentation with this protocol, especially in
   combination with Transport Layer Security (TLS) [RFC2246], to help
   determine how TLS may effectively be used as a security layer for
   IPP.

ABSTRACT

   This document is one of a set of documents, which together describe
   all aspects of a new Internet Printing Protocol (IPP).  IPP is an
   application level protocol that can be used for distributed printing
   using Internet tools and technologies. This document describes IPP
   from a high level view, defines a roadmap for the various documents
   that form the suite of IPP specifications, and gives background and
   rationale for the IETF working group's major decisions.

Zilles                        Experimental                      [Page 1]
RFC 2568                   Rationale for IPP                  April 1999

   The full set of IPP documents includes:

      Design Goals for an Internet Printing Protocol [RFC2567]
      Rationale for the Structure and Model and Protocol for the
      Internet Printing Protocol (this document)
      Internet Printing Protocol/1.0: Model and Semantics [RFC2566]
      Internet Printing Protocol/1.0: Encoding and Transport [RFC2565]
      Internet Printing Protocol/1.0: Implementer's Guide [ipp-iig]
      Mapping between LPD and IPP Protocols [RFC2569]

   The "Design Goals for an Internet Printing Protocol" document takes a
   broad look at distributed printing functionality, and it enumerates
   real-life scenarios that help to clarify the features that need to be
   included in a printing protocol for the Internet.  It identifies
   requirements for three types of users: end users, operators, and
   administrators.  The Design Goals document calls out a subset of end
   user requirements that are satisfied in IPP/1.0. Operator and
   administrator requirements are out of scope for version 1.0.

   The "Internet Printing Protocol/1.0: Model and Semantics" document
   describes a simplified model consisting of abstract objects, their
   attributes, and their operations that is independent of encoding and
   transport.  The model consists of a Printer and a Job object.  The
   Job optionally supports multiple documents.  This document also
   addresses security, internationalization, and directory issues.

   The "Internet Printing Protocol/1.0: Encoding and Transport" document
   is a formal mapping of the abstract operations and attributes defined
   in the model document onto HTTP/1.1.  It defines the encoding rules
   for a new Internet media type called "application/ipp".

   The "Internet Printing Protocol/1.0: Implementer's Guide" document
   gives insight and advice to implementers of IPP clients and IPP
   objects.  It is intended to help them understand IPP/1.0 and some of
   the considerations that may assist them in the design of their client
   and/or IPP object implementations.  For example, a typical order of
   processing requests is given, including error checking.  Motivation
   for some of the specification decisions is also included.

   The "Mapping between LPD and IPP Protocols" document gives some
   advice to implementers of gateways between IPP and LPD (Line Printer
   Daemon) implementations.

1.   ARCHITECTURAL OVERVIEW

   The Internet Printing Protocol (IPP) is an application level protocol
   that can be used for distributed printing on the Internet.  This
   protocol defines interactions between a client and a server.  The