RFC 1821 (rfc1821) - Page 2 of 24

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

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
   mind, a real-time service environment is an integral part of the
   protocol. With the approval of UNI 3.1 by the ATM Forum, the ATM
   standards now have several categories of service. Given the wide
   acceptance of ATM by the long-line carriers, the use of ATM in the
   Internet is, if not guaranteed, highly likely. The question now
   becomes, how can we successfully interface between the real-time
   services offered by ATM and the new,integrated service environment
   soon to be available in the IP protocol suite. The current IP over
   ATM standards assume no real-time IP protocols. It is the purpose of
   this RFC to clearly delineate what the issues are in integrating
   real-time services in an IP-over-ATM network [10,15,19,20,21].



Borden, et al                Informational