I think you refer to authenticating squid user against a radius server... In which case freeradius has a role in proxying, but I don't see any case where squid could have a role in AAA process.
Maybe you could point us to a document that would explain things a bit more?

2011/6/10 arpitha arpitha <arpithaarp@gmail.com>
what's the role of Squid in a radius runnin server, i know its related
to proxy thing but would like to 've more info.
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