Xunet 2: lessons from an early wide-area ATM testbed

Abstract

-This paper is a retrospective on the design of Xunet 2, one of the earliest functional wide-area ATM networks. Work on Xunet 2 began in 1989 and the network, consisting of experimental ATM switches, IP routers, and 45 Mbps transmission lines, has been operational since October 1991. The network serves as a ''laboratory without walls'' for eight research groups across the United States. While Xunet 2 has only a small number of nodes, it was designed as a prototype of a nationwide ATM network. This paper reviews some of the design decisions and lessons learned in the project and points out the research directions motivated by this work, focusing on the areas of traffic management, ATM switch design, network control, and the implementation of an IP router.

An efficient ATM voice service with flexible jitter and delay guarantees

“…Some options for this append process are: 1) to increase the word length across the switch fabric or 2) to temporarily use some VPI/VCI header bits while the cell traverses the fabric. Such networkspecific use of ATM header bits has been reported [16] for a wide-area ATM testbed where an 8-bit congestion field was utilized.…”

“…The lower bound has been proposed by ITU-T for terrestrial connections. A much stricter two-way delay bound (15)(16)(17)(18)(19)(20)(21)(22)(23)(24)(25)(26)(27)(28)(29)(30) ms is required for voice calls using analog terminals, which includes 95 of all phones [2]. Longer delays generate significant talker echo due to impedance mismatches at the subscriber loop [5].…”