RFC 1821 (rfc1821) - Page 2 of 24
Integration of Real-time Services in an IP-ATM Network Architecture
Alternative Format: Original Text Document
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