Whats is MSAU?

In a Token Ring network, a multi station access unit (MSAU) is used in place of the hub that is used on an Ethernet network. The MSAU performs the token circulation inside the device, giving the network a physical star appearance. Each MSAU has a Ring in (RI) port on the device, which is connected to the Ring out (RO) port on another MSAU. The last MSAU in the ring is then connected to the first to complete the ring. Because Token Ring networks are few and far between nowadays, it is far more likely that you will find yourself working with Ethernet hubs and switches.