Passive Performance Monitoring and Traffic Characteristics on the SLAC Internet Border

Understanding how the Internet is used by HEP is critical to optimizing the performance of the inter-lab computing environment. Typically use requirements have been defined by discussions between collaborators. However, later analysis of the actual traffic has shown this is often misunderstood and actual use is significantly different to that predicted. Passive monitoring of the real traffic provides insight into the true communications requirements and the performance of a large number of inter-communicating nodes. It may be useful in identifying performance problems that are due to factors other than Internet congestion, especially when compared to other methods such as active monitoring where traffic is generated specifically to measure its performance. Controlled active monitoring between dedicated servers often gives an indication of what can be achieved on a network. Passive monitoring of the real traffic gives a picture of the true performance. This paper will discuss the method and results of collecting and analyzing flows of data obtained from the SLAC Internet border. The unique nature of HEP traffic and the needs of the HEP community will be highlighted. The insights this has brought to understanding the network will be reviewed and the benefit it can bring to engineering networks will be discussed.