Introduction

Asynchronous Transfer Mode (ATM) technology was originally developed for the high-speed and low Bit Error Rate(BER) environment. As ATM technology was deployed, interest in using ATM over satellite links has emerged. However, satellite Links have characteristics different from the environment for which ATM was designed. There are various alternatives for transporting ATM cells over satellite links. Typically, to select a specific transport mechanism, end-users, service providers, or network designers have to consider the performance impacts, bandwidth utilization, power requirements, operations and reliability aspects. For example, to improve the physical layer performance, and hence the performance of higher layers of the ATM stack, a user may employ a powerful FEC mechanism at the satellite modem. Conversely, another user may choose to employ some other network solution that combines more efficient power and bandwidth techniques. This document addresses the latter solution as it introduces a network device that provides powerful, dynamic FEC and data compression techniques for better bandwidth utilization. This CASI provides the specifications for implementing a network device between the terrestrial ATM network interface and a conventional satellite modem. This CASI will allow interoperability among different vendor equipment that provides the features that are described in this document.

There are various standards for ATM that have been developed by the ATM Forum (ATM-F) and the International Telecommunication Union (ITIJ). In particular, the ATM Forum has developed the "Traffic Management Specification (TM 4.0). The TM specification contains sections on ATM service architecture, Quality of Service, Traffic Contract, and procedures for traffic management. On the other hand, the ITU-Telecommunication Sector has developed a series of recommendations on ATM that deal with reference architectures, congestion control, network interfaces, performance, operations and maintenance principles, etc. Two recommendations that deal with network performance and architecture issues are ITU-T Recommendation 1.356 "B-ISDN ATM Layer Cell Transfer Performance" and ITU-R Recommendation S.{Doc.4/44] ("Performance for B-ISDN ATM via Satellite"). As noted previously, this document describes a CASI for interconnecting terrestrial ATM network elements to conventional satellite modems.