SPAND: Shared Passing Network Discovery

In the Internet today, it is difficult to determine in advance what the network performance between a pair of internet hosts will be. There are several examples of applications that could use this information if it were made available to them:

• Clients that must choose between servers that replicate the same content.
• Servers that present clients with differences in content fidelity of web objects.
• Applications that present feedback to the user about the quality of connectivity.

SPAND is a software toolkit that makes it easy for networked applications to report the performance they percieve as they communicate with distant internet hosts and remember this information for later use. As clients communicate with other hosts, they generate Performance Reports that summarize how their connection progressed. For example, clients may report the average throughput of a TCP connection or the download time for a particular web page. These Performance Reports are sent to a per-domain Performance Server who acts as a repository of all the Performance Reports for clients in the domain. Later, other clients contact the Performance Server with a Performance Query , asking about the performance to a distant network site. The Performance Server replies with a Performance Response which gives the average performance (and variance of performance) seen by clients in this domain.