RSVP over ATM Implementation Guidelines
RFC 2379

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Network Working Group                                          L. Berger
Request for Comments: 2379                                  FORE Systems
BCP: 24                                                      August 1998
Category: Best Current Practice

                RSVP over ATM Implementation Guidelines

Status of this Memo

   This document specifies an Internet Best Current Practices for the
   Internet Community, and requests discussion and suggestions for
   improvements.  Distribution of this memo is unlimited.

Copyright Notice

   Copyright (C) The Internet Society (1998).  All Rights Reserved.

Abstract

   This memo presents specific implementation guidelines for running
   RSVP over ATM switched virtual circuits (SVCs).  The general problem
   is discussed in [6].  Implementation requirements are discussed in
   [2].  Integrated Services to ATM service mappings are covered in [3].
   The full set of documents present the background and information
   needed to implement Integrated Services and RSVP over ATM.

1. Introduction

   This memo discusses running IP over ATM in an environment where SVCs
   are used to support QoS flows and RSVP is used as the internet level
   QoS signaling protocol.  It applies when using CLIP/ION, LANE2.0 and
   MPOA methods for supporting IP over ATM.  The general issues related
   to running RSVP[4] over ATM have been covered in several papers
   including [6] and other earlier work.  This document is intended as a
   companion to [6,2] and as a guide to implementers.  The reader should
   be familiar with both documents.

   This document provides a recommended set of functionality for
   implementations using ATM UNI3.x and 4.0, while allowing for more
   sophisticated approaches.  We expect some vendors to additionally
   provide some of the more sophisticated approaches described in [6],
   and some networks to only make use of such approaches.  The
   recommended set of functionality is defined to ensure predictability
   and interoperability between different implementations.  Requirements
   for RSVP over ATM implementations are provided in [2].

Berger                   Best Current Practice                  [Page 1]
RFC 2379        RSVP over ATM Implementation Guidelines      August 1998

   This document uses the same terms and assumption stated in [2].
   Additionally, 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 RFC
   2119 [5].

2. Implementation Recommendations

   This section provides implementation guidelines for implementation of
   RSVP over ATM.  Several recommendations are common for all, RSVP
   sessions, both unicast and multicast.  There are also recommendations
   that are unique to unicast and multicast session types.

2.1 RSVP Message VC Usage

   The general issues related to which VC should be used for RSVP
   messages is covered in [6]. It discussed several implementation
   options including: mixed control and data, single control VC per
   session,  single control VC multiplexed among sessions, and multiple
   VCs multiplexed among sessions.  QoS for control VCs was also
   discussed.  The general discussion is not repeated here and [6]
   should be reviewed for detailed information.

   RSVP over ATM implementations SHOULD send RSVP control (messages)
   over the best effort data path, see figure 1.  It is permissible to
   allow a user to override this behavior.  The stated approach
   minimizes VC requirements since the best effort data path will need
   to exist in order for RSVP sessions to be established and in order
   for RSVP reservations to be initiated.  The specific best effort
   paths that will be used by RSVP are: for unicast, the same VC used to
   reach the unicast destination; and for multicast, the same VC that is
   used for best effort traffic destined to the IP multicast group.
   Note that for multicast there may be another best effort VC that is
   used to carry session data traffic, i.e., for data that is both in
   the multicast group and matching a sessions protocol and port.

Berger                   Best Current Practice                  [Page 2]
RFC 2379        RSVP over ATM Implementation Guidelines      August 1998

                            Data Flow ==========>

                                   QoS VCs
                    +-----+    -------------->   +----+
                    |     |  -------------->     |    |
                    | Src |                      | R1 |
                    |     |   Best Effort VC(s)  |    |
                    +-----+  <-----------------> +----+
                                 /\
                                 ||
                                 ||
                             RSVP Control
                               Messages

                  Figure 1: RSVP Control Message VC Usage