Squid is a web proxy cache. This means that it will cache HTTP and FTP downloads locally to speed up downloads for client. Some VDT users are planning on using Squid to allow clients to cache tarballs that they download for each job. Note that to use squid, clients must configure their HTTP or FTP client to know about the existence of the cache: the VDT does not configure Squid to do transparent proxying.
We recommend installing Squid on a separate computer from the computer that accepts incoming jobs (the gatekeeper) for two reasons: First, the gatekeper is often heavily loaded and we do not want any impact from Squid, even if it is small. Second, we want to isolate security flaws in software on the gatekeeper from Squid, and vice-versa.