Network operators have a fairly good idea about how well their networks are working on a macro level -- link downtime percentages, ping latencies, CPU utilization, etc. However, few have examined the fine-grained behavior of their networks. We have collected high-resolution (20 microseconds) jitter measurements on a wide-area backbone network for a duration of several weeks. Based on this data, we claim that today's wide-area backbone networks are ready to support applications such as circuit emulation over IP -- or they could be, as this example shows.

We observed that most of the time the jitter level is quite low, making the data very uniform. But very occasionally there are extremely interesting events that last from a few seconds to a few minutes. In particular, we detected sustained routing loops in IS-IS, which should not occur. We will show the surprising effect this has on the data, and examine some protocol anomalies that may have been the cause. If these rare problems are corrected, low-latency, low-loss Virtual Wire services can be supported.

About the Presenter
Stephen L. Casner received his B.A. in Mathematics from Occidental College in 1973 and his M.S. in Computer Science from the University of Southern California in 1976, where he designed and implemented protocols and software for some of the earliest experiments with packet voice using the ARPAnet at USC's Information Sciences Institute. He took this work to the commercial arena with further development of packet-based audio and video technology for both conferencing and streaming applications at Precept Software, which was acquired by Cisco Systems. Currently at Packet Design, he is applying some of the same techniques in network performance measurement and analysis. He is also co-chairman of the Audio/Video Transport working group of the Internet Engineering Task Force. This group has developed the Real-time Transport Protocol (RTP) for packet audio and video as well as other real-time multicast and unicast applications. He was the primary organizer for the establishment of the worldwide Mbone in its initial experimental phase.