datatracker.ietf.org
Sign in
Version 5.7.1.p2, 2014-10-29
Report a bug

Remote Service Discovery in the Service Location Protocol (SLP) via DNS SRV
RFC 3832

Document type: RFC - Experimental (July 2004; No errata)
Was draft-zhao-slp-remote-da-discovery (individual in int area)
Document stream: IETF
Last updated: 2013-03-02
Other versions: plain text, pdf, html

IETF State: (None)
Consensus: Unknown
Document shepherd: No shepherd assigned

IESG State: RFC 3832 (Experimental)
Responsible AD: Thomas Narten
Send notices to: <zwb@cs.columbia.edu>

Network Working Group                                            W. Zhao
Request for Comments: 3832                                H. Schulzrinne
Category: Experimental                               Columbia University
                                                              E. Guttman
                                                        Sun Microsystems
                                                            C. Bisdikian
                                                               W. Jerome
                                                                     IBM
                                                               July 2004

                    Remote Service Discovery in the
              Service Location Protocol (SLP) via DNS SRV

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 (2004).

Abstract

   Remote service discovery refers to discovering desired services in
   given remote (i.e., non-local) DNS domains.  This document describes
   remote service discovery in the Service Location Protocol (SLP) via
   DNS SRV.  It defines the DNS SRV Resource Records for SLP Directory
   Agent services, discusses various issues in using SLP and DNS SRV
   together for remote service discovery, and gives the steps for
   discovering desired services in remote DNS domains.

1.  Introduction

   This document describes remote service discovery in the Service
   Location Protocol (SLP) [RFC2608] via DNS SRV [RFC2782].  We consider
   remote service discovery as discovering desired services in given
   remote DNS domains, and local service discovery as discovering
   desired services within the local administrative domain.

   SLP provides a scalable framework for local service discovery and
   selection.  In SLP, User Agents (UAs) discover desired services in
   the local administrative domain by querying all Service Agents (SAs)
   via multicast or querying a Directory Agent (DA) via unicast.  To

Zhao, et al.                  Experimental                      [Page 1]
RFC 3832          Remote Discovery in SLP via DNS SRV          July 2004

   query a DA using unicast, a UA needs to first learn about the DA via
   DHCP, static configuration or multicast (listening for DAAdvert
   multicast or issuing DA discovery SrvRqst multicast).

   DNS SRV provides good support for remote service discovery.  However,
   if multiple servers are discovered via DNS SRV for a service, only
   priority and weight can be used to make a selection.  If additional
   service properties (such as cost, speed and service quality) need to
   be considered in the selection process, DNS SRV becomes insufficient.

   We propose that using SLP and DNS SRV together can provide better
   support for remote service discovery.  First, a UA uses DNS SRV to
   find SLP DAs at a remote DNS domain.  Then, the UA uses SLP to query
   one of those DAs to discover desired services.  In this way, we can
   avoid the limitations in using SLP and DNS SRV separately.  On one
   hand, without DNS SRV, an SLP UA needs to depend on static
   configuration to learn about remote DAs because DHCP and multicast DA
   discovery are not generally applicable beyond the local
   administrative domain.  On the other hand, without SLP, DNS SRV has
   limited support for service selection.

   In this document, we first define the DNS SRV Resource Records (RRs)
   for SLP DA services, which are used to map a given DNS domain to
   remotely accessible (i.e., accessible from the Internet) DAs in that
   domain.  Then, we discuss various issues in using SLP and DNS SRV
   together for remote service discovery.  Finally, we give the steps
   for discovering services in remote DNS domains.

1.1.  Notation Conventions

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
   document are to be interpreted as described in BCP 14, RFC 2119
   [RFC2119].

2.  The DNS SRV RRs for SLP DA services

   According to RFC 2782 [RFC2782], the DNS SRV RRs for SLP DA services
   are defined as follows:

   _slpda._Proto.Name TTL Class SRV Priority Weight Port Target

   where "slpda" is the symbolic name for SLP DA services, the Proto
   field is either "tcp" or "udp", and the Target field is the domain
   name of an SLP DA.  Please refer to [RFC2782] for detailed
   explanation of each field in DNS SRV RRs.

[include full document text]