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Service Location Working Group                             Jonathan Wood
INTERNET DRAFT                                     Sun Microsystems, Inc
                                                           9 August 1999

                    The wpad Abstract Service Type

Status of This Memo

   This document is a submission by the Service Location Working Group
   of the Internet Engineering Task Force (IETF).  Comments should be
   submitted to the srvloc@srvloc.org mailing list.

   Distribution of this memo is unlimited.

   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, and its working groups.  Note that
   other groups may also distribute working documents as

   Internet-Drafts are draft documents valid for a maximum of six
   months and may be updated, replaced, or obsoleted by other
   documents at any time.  It is inappropriate to use Internet-
   Drafts as reference material or to cite them other than as
   "work in progress."

   The list of current Internet-Drafts can be accessed at

   The list of Internet-Draft Shadow Directories can be accessed at


   This document describes the wpad abstract type. The wpad service
   provides access to web proxy auto-discovery (WPAD) configuration
   files (CFILEs). This service type can be used in conjunction with
   the Service Location Protocol (SLP) to dynamically retrieve CFILEs
   which can automatically configure web browsers with suitable web

1. Introduction

   The Service Location Protocol is defined in [1]. Service templates

Wood, Tam                expires February 2000                  [Page 1]

INTERNET DRAFT                                               August 1999

   and abstract types are defined in [2]. The wpad abstract type is
   intended to organize information pertaining to the location and
   access method needed to dynamically obtain CFILEs. For more
   information on CFILEs and WPAD, see [3].

   The content of the WPAD file is opaque as far as this service type
   is concerned. Different browsers may interpret CFILEs in
   different ways. Hence customized CFILEs may be needed to
   service various browsers. A "config-method" attribute is specified
   in the template to allow web browsers to use SLP to search for
   a suitable CFILE.

   CFILEs tell web browsers which web proxies are available, and
   how to select the proper one for its needs. This service type does
   NOT contain any information about how to directly access web proxies.

   Similarly, CFILEs do NOT contain any configuration information
   for other web browser functions. The wpad service is not an
   application configuration service.

   The concrete type should be the access protocol used to retrieve
   the CFILE. The URL should also specify the host that provides
   access to the CFILE, and a path relative to the server host
   that names the location of the CFILE. An example of a valid
   wpad service: URL follows:


   A configuration URL (CURL) as defined in [3] can be extracted from
   this service: URL simply by removing the leading "service:".

2. The "wpad" Abstract Service

  Name of submitter: "Jonathan Wood" <jonathan.wood@eng.sun.com>

  Language of service template: en

  Security Considerations: If a web browser is tricked into retrieving
  a malicious CFILE, it could suffer denial-of-service attacks, or
  potentially betray confidential information. As such, the web browser
  should take care to ensure that the CFILE is not malicious. The use
  of SLP's protected scopes is a means of ensuring a CFILE's validity.

  Template text:

  -------------------------template begins here-----------------------

Wood, Tam                expires February 2000                  [Page 2]

INTERNET DRAFT                                               August 1999


    This is an abstract service type for WPAD configuration URLs.

    url-path= ; an URL for the configuration data, as defined in [4].

  config-method= string M X
  # The method of determining the configuration.
  # Since this may vary from browser to browser, clients should
  # include this attribute in search requests to ensure that they
  # get a configuration method that will be applicable to their
  # specific browser.
  # The values must refer to a browser type. If two different browsers
  # use the same configuration method, they may use the same value for
  # this attribute. For example, if Wiz Software creates a new browser
  # that uses the same method as Netscape's Communicator (i.e.
  # Javascript), it may use the "communicator" value.

  access-protocol= string
  # The protocol to be used to access this CFILE. This attribute
  # is useful for UAs which wish to query for a set of preferred
  # access protocols. This attribute should match the access protocol
  # given in the concrete type.

  --------------------------template ends here------------------------


    [1] E. Guttman, C. Perkins, J. Veizades, M. Day,
        "Service Location Protocol Version 2", RFC 2608, June 1999.

    [2] E. Guttman, C. Perkins, J. Kempf, "Service Templates and
        service: Schemes", RFC 2609, June 1999.

    [3] P. Gauthier, J. Cohen, M. Dunsmuir, C. Perkins, "Web Proxy
        Auto-Discovery Protocol", Internet Draft, July 1999 (Work
        In Progress)

    [4] T. Berners-Lee, R. Fielding, and L. Masinter.  Uniform Resource
        Locators (URL): Generic Syntax and Semantics.  RFC1738 as
        amended by RFC1808

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