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
