It is increasingly the case that a given internet interaction can be satisfied by one of a number of internet hosts. In any such interaction a major factor in choosing which host to access is the distance between the interacting hosts.
Distance here refers to some internet performance metrics such as latency or bandwidth.
The benefit of factoring in distance in the choice of which replicated web server or web cache to access is apparent. While hosts can measure characteristics of paths using various tools such as ping , traceroute , pathchar , mtrace , etc., having each host conduct performance measurements prior to each internet interaction inevitably leads to high overhead both to the host and to the internet. Hence a useful service for the internet would be one whereby a host could quickly and efficiently learn the distance between two other hosts. To be widely useful, such a service should provide an answer with a delay and overhead less than those of the gains achieved by using the service. This material is based upon work supported by the National Science Foundation under Grant No. 9876541.