XUNET-2 - LESSONS FROM AN EARLY WIDE-AREA ATM TESTBED

This paper is a retrospective on the design of Xunet 2, one of the ear liest functional wide-area asynchronous transfer mode (ATM) networks. Work on Xunet 2 began in 1989 and the network, consisting of experimen tal ATM switches, IP renters, and 45 Mb/s transmission lines, has been operational since October 1991. The network serves as a ''laboratory without walls'' for eight research groups across the United States. Wh ile Xunet 2 has only a small number of nodes, it was designed as a pro totype of a nationwide ATM network. This paper reviews some of the des ign decisions and lessons learned in the project and points out the re search directions motivated by this work, focusing on the areas of tra ffic management, ATM switch design, network control, and the implement ation of an IP router.