If kept intact, a full class C network has a subnet mask of 255.255.255.0. If a class C network is divided in half, each half of the class C would have 128 IP addresses, each with a subnet mask of 255.255.255.128. Token ring is a LAN with individual links that form a circle. A token is passed around the ring and only the device that has the token can send data. A bridge is a device that connects two or more physical networks and forwards packets between them.
Bridges can usually filter packets - that is, forward only certain traffic.
Routing Information Protocol, a type of protocol a router can use to communicate with other routers. A formal description of message formats and the rules two or more systems must follow to exchange those messages. Protocol definitions range from how bits are placed on a wire to the format of an e-mail message. Standard protocols allow different manufacturers' computers to communicate. The computers can use completely different software, provided each computer's software can agree upon the meaning of the data.