Protocol - A protocol is a set of rules that governs the communications between computers on a network. These rules include guidelines that regulate the following characteristics of a network: access method, allowed physical topologies, types of cabling, and speed of data transfer.

-The most common protocol used in a computer network is the Ethernet protocol.
-Another common protocol for computer networks is the LocalTalk protocol. This protocol was designed by Apple Computer Inc, for Macintosh computers.
-Token Ring is another example of a network protocol. This was developed by IBM in the 1980's.
-FDDI or Fiber Distributed Data Interface is a network protocol that is used primarily to interconnect two or more local area networks, often over large distances.
-ATM is an Asynchronous Transfer Mode is that transmits data at a speed of 155 Mbps and higher.

2. Describe the Ethernet protocol. Distinguish between fast Ethernet and gigabit Ethernet.

a) The Ethernet protocol is by far the most widely used. Ethernet uses an access method called CSMA/CD (Carrier Sense Multiple Access/Collision Detection). This is a system where each computer listens to the cable before sending anything through the network. If the network is clear, the computer will transmit. If some other node is already transmitting on the cable, the computer will wait and try again when the line is clear. Sometimes, two computers attempt to transmit at the same instant. When this happens a collision occurs. Each computer then backs off and waits a random amount of time before attempting to retransmit. With this access method, it is normal to have collisions. However, the delay caused by collisions and retransmitting is very small and does not normally effect the speed of transmission on the network. The Ethernet protocol allows for linear bus, star, or tree topologies. Data can be transmitted over twisted pair, coaxial, or fiber optic cable at a speed of 10 Mbps.

b) Fast Ethernet - To allow for an increased speed of transmission, the Ethernet protocol has developed a new standard that supports 100 Mbps. This is commonly called Fast Ethernet. Fast Ethernet requires the use of different, more expensive network concentrators/hubs and network interface cards. In addition, category 5 twisted pair or fiber optic cable is necessary. Fast Ethernet is becoming common in schools that have been recently wired.

Gigabit Ethernet - The most recent development in the Ethernet standard is a protocol that has a transmission speed of 1 Gbps. Gigabit Ethernet is primarily used for backbones on a network at this time. In the future, it will probably be used for workstation and server connections also. It can be used with both fiber optic cabling and copper. The 1000BaseTX, the copper cable used for Gigabit Ethernet, is expected to become the formal standard in 1999.