Integration of Real-time Services in an IP-ATM Network Architecture
RFC 1821

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Network Working Group                                          M. Borden
Request for Comments: 1821                                    E. Crawley
Category: Informational                                     Bay Networks
                                                                B. Davie
                                                                Bellcore
                                                              S. Batsell
                                                                     NRL
                                                             August 1995

  Integration of Real-time Services in an IP-ATM Network Architecture

Status of the Memo

   This memo provides information for the Internet community.  This memo
   does not specify an Internet standard of any kind. Distribution of
   this memo is unlimited.

Abstract

   The IETF is currently developing an integrated service model which is
   designed to support real-time services on the Internet.
   Concurrently, the ATM Forum is developing Asynchronous Transfer Mode
   networking which similarly provides real-time networking support. The
   use of ATM in the Internet as a link layer protocol is already
   occurring, and both the IETF and the ATM Forum are producing
   specifications for IP over ATM. The purpose of this paper is to
   provide a clear statement of what issues need to be addressed in
   interfacing the IP integrated services environment with an ATM
   service environment so as to create a seamless interface between the
   two in support of end users desiring real-time networking services.

Table of Contents

   1.0 Introduction                                                2
   2.0 Problem Space Overview                                      3
   2.1 Initial Assumptions                                         3
   2.2 Topologies Under Consideration                              4
   2.3 Providing QoS in IP over  ATM - a walk-though               5
   3.0 Service Model Issues                                        6
   3.1 Traffic Characterization                                    7
   3.2 QoS Characterization                                        8
   4.0 Resource Reservation Styles                                10
   4.1 RSVP                                                       10
   4.2 ST-II                                                      13
   4.3 Mapping IP flows to ATM Connections                        15
   5.0 End System Issues                                          16
   6.0 Routing Issues                                             16

Borden, et al                Informational                      [Page 1]
RFC 1821          Real-time Service in IP-ATM Networks       August 1995

   6.1 Multicast routing                                          17
   6.2 QoS Routing                                                17
   6.3 Mobile Routing                                             18
   7.0 Security Issues                                            19
   8.0 Future Directions                                          20
   9.0 References                                                 22
   10.0 Authors' Addresses                                        24

1.0 Introduction

   The traditional network service on the Internet is best-effort
   datagram transmission. In this service, packets from a source are
   sent to a destination, with no guarantee of delivery. For those
   applications that require a guarantee of delivery, the TCP protocol
   will trade packet delay for correct reception by retransmitting those
   packets that fail to reach the destination. For traditional
   computer-communication applications such as FTP and Telnet in which
   correct delivery is more important than timeliness, this service is
   satisfactory. However, a new class of application which uses multiple
   media (voice, video, and computer data) has begun to appear on the
   Internet. Examples of this class of application are video
   teleconferencing, video-on-demand, and distributed simulation. While
   these applications can operate to some extent using best-effort
   delivery, trading packet delay for correct reception is not an
   acceptable trade-off. Operating in the traditional mode for these
   applications results in reduced quality of the received information
   and, potentially, inefficient use of bandwidth. To remedy this
   problem the IETF is developing a real-time service environment in
   which multiple classes of service are offered [6]. This environment
   will greatly extend the existing best-effort service model to meet
   the needs of multimedia applications with real-time constraints.

   At the same time that this effort is underway in the IETF,
   Asynchronous Transfer Mode (ATM) is being developed, initially as a
   replacement for the current telephone network protocols, but more
   recently as a link-layer protocol for computer communications. As it
   was developed from the beginning with telephone voice applications in