Media Access Unit

An IBM 8228 Media Access Unit

A Media Access Unit (MAU, also called Multistation Access Unit, MSAU) is a device to attach multiple network stations in a star topology in a token ring network, internally wired to connect the stations into a logical ring. The MAU contains relays to short out nonoperating stations. Multiple MAUs can be connected into a larger ring through their Ring In/Ring Out connectors.

MAU's are also called the "Ring in a Box". The loop that used to make up the ring of the Token ring is now integrated into the chip. In Token ring, when a link is broken in the ring, the entire network goes down; however with an MAU, the broken circuit is immediately closed off (within 1ms) allowing stations on the ring to have their cords unplugged without crashing the entire network.

MAU in this context is not to be confused with a Medium Attachment Unit, which shares the same acronym.


This article was originally based on material from the Free On-line Dictionary of Computing, which is licensed under the GFDL.