Manual:$wgHTCPMulticastAddress/en

Details
Deprecated. Setting first appeared in 1.4.1, but was commented out in. Set to false from 1.9.0. Replaced by  in MediaWiki 1.20 and   in MediaWiki 1.22 and subsequent versions.

HTCP is a method of purging entries from the Squid cache that can use multicast and udp which is faster then opening an http connection to every squid server.

The  variable is deprecated as of MediaWiki 1.20.0 but is still recognized by being copied to the new one in :