RFC 3059 (rfc3059) - Page 2 of 6

Attribute List Extension for the Service Location Protocol

RFC 3059           Attribute List Extension for SLPv2      February 2001


1. Introduction

   The Service Location Protocol, Version 2 [3] provides a mechanism for
   a service to be discovered in a single exchange of messages.  The UA
   sends a Service Request message and the DA or SA (as appropriate)
   sends a Service Reply message.

   It is clearly advantageous to be able to obtain all service
   information at once.  The Service Location Protocol separates
   messages which obtain different classes of information.  This
   extension enables an optimization to the basic exchange of messages,
   which currently does not include service attributes in Service Reply
   messages.

   This document specifies a SLPv2 extension which allows a UA to
   request that a service's attributes be included in Service Reply
   messages.  This will eliminate the need for multiple round trip
   messages for a UA to acquire all service information.

   If the DA or SA does not support the Attrlist extension, it will
   simply return a Service Reply (without the extension).  Support of
   this extension is OPTIONAL.  Existing implementations will ignore the
   Attrlist extension since it has been assigned a identifying number
   from the range which indicates that the receiver MUST ignore the
   extension if it is not recognized.  See RFC 2608 [3].

   If the UA receives a Service Reply message without an Attrlist
   Extension it must assume the SA or DA does not support the extension.
   In this case, the UA must send an Attribute Request for each URL it
   obtains in the Service Reply message in order to obtain the
   attributes for these services.

1.1. Terminology

   User Agent (UA)
         A process working on the user's behalf to establish contact
         with some service.  The UA retrieves service information from
         the Service Agents or Directory Agents.

   Service Agent (SA)
         A process working on the behalf of one or more services to
         advertise the services.

   Directory Agent (DA)
         A process which collects service advertisements.  There can
         only be one DA present per given host.





Guttman                     Standards Track