Media access unit
A media access unit (MAU), also known as a multistation access unit (MAU or MSAU) is a device to attach multiple network stations in a star topology as a token ring network, internally wired to connect the stations into a passive (i.e. non-switched and unmanaged) logical ring.
Passive token ring was an active IBM networking product in the 1997 time-frame, after which it was rapidly displaced by switched networking.
MAU contains relays to short out non-operating stations. Multiple MAUs can be connected into a larger ring through their ring in/ring out connectors.
MAU is also called a "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 disabling the entire network.
Advantages and limitations
This networking technology supported large geographic areas (with a total ring circumference of several kilometers), but the bandwidth was shared by all stations, and thus this technology was soon displaced by high-bandwidth switched networks.
- IBM (1997). "LAN Hub Sales Guide".
- IBM (1997). "Token-Ring Migration to Switched LAN Interconnect — A Technical White Paper".
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