Automatically Selecting a Close Mirror Based on Network Topology

The content of many popular ftp and web sites on the Internet are replicated at other sites, called ‘‘mirrors’’; typically, to decrease the network load at the original site, to make information available closer to its users for higher availability; and to decrease the bandwidth requirements these sites place on long-haul network connections, such as international and backbone links. Even though the success of mirroring depends heavily on the selection of a good mirror, there are very few methods to pick a good mirror: i.e., a mirror ‘‘close’’ to its user based on network topology. This paper describes a method and two tools developed to locate a ‘‘close’’ mirror among replicated copies of a network service such as ftp, www, irc, streaming audio by utilizing network topology information based on autonomous systems. Routing information from the Internet Routing Registry is combined with information about the location of mirrors to generate mirroring tables, similar to routing tables, which are used to identify a ‘‘close’’ mirror, where ‘‘close’’ is defined as traversing the minimum number of autonomous systems. The tools are avaliable via anonymous ftp from ftp.coubros.com .