1 LAN Traffic Measurements Carey Williamson Department of Computer Science University of Calgary

2 Introduction l Some of the first network traffic measurement papers were for measurements done on Ethernet local area networks (LAN’s) l We will look at one such example: l Riccardo Gusella, ‘‘A Measurement Study of Diskless Workstation Traffic on an Ethernet Local Area Network”, 1988

3 Overview l Studied campus LAN environment at U.C. Berkeley l Medium size Ethernet LAN l About 100 workstations l Consists of file servers, and diskless workstations

4 Measurement Tools l VAX 8600 mainframe dedicated for data collection l 32 Mbyte RAM l Dual buffering strategy, with memory to disk to tape storage system l Three weeks of trace collection l 6.5 Gigabytes of trace data

5 Measurement Tools (Cont’d) l Results are reported for one 24-hour packet trace (11.8 million packets) l Highly detailed and accurate study l Extract all protocol info from traces l Microsecond resolution for timestamps l Less than 1% packet loss

6 Main Observations l Average Ethernet utilization is higher than that reported in earlier studies l Traffic patterns highly skewed l Single workstations can dominate l Packet size distribution bimodal l Definite spikes in interarrival times l Packet arrival rate varies a lot (bursty)

7 Per Protocol Analysis l One of the novel aspects of Gusella’s work was a complete breakdown of the results by protocol type (e.g., TCP, UDP, NFS, ND) l Able to identify characteristics in traffic that can be linked to specific protocols and/or machines l Possible because of high resolution timestamps and complete protocol info

8 Summary l Gusella’s work was one of the first detailed studies of Ethernet LAN traffic l Had excellent measurement tools, high resolution timers, lots of storage l Identified traffic characteristics common to most campus LAN environments l Identified impact of new workstation technologies, protocols, applications on network load