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CT037-3-2-NWS

LAN Protocols

LAN Protocols1) Explain Ethernet, Token Ring and Fiber Distributed Data interface (FDDI) in detail,

mentioning their properties and strength.

2) Define LLC and MAC, their functions and their interactions with each other and other

layers.

3) How is media access controlled in order to avoid collisions? Describe each of these

methods and protocols.

4) What are the differences between a switch and a bridge?

5) What is the relevance between CSMA/CD and Duplex mode(full or half-duplex)?

Answer

1) Ethernet is a protocol (IEEE 802.3) for the local area network (LAN) to controls the way

data is transmitted. It typically uses coaxial cable or special grades of the twisted pair wire

The commonly installed Ethernet systems are called 10BASE-T and provide transmission

speeds up to 10 Mbps. Typically used for LAN backbone system is fast Ethernet or

100BASE-T provides transmission speeds up to 100 mbps. For a higher level of backbone

support at 1000 mbps is provided by the gigabit Ethernet.

Token Ring (IEEE 802.5) is the token passing around the networks. It will move a small frame

nside the token. Each node will hold the token for a maximum period. It will have few statuses

his:

If a node receive a token which is empty, and have information to send. The information

will put in the token and pass to the next node.

If a node receive a token which is empty, and no information to send. The token will pa

to the next node.

If a node receive a token and it is not empty, the node will check is it the information w

belong to it or not? If not will pass to next node. If yes will get the information and pass thnode to the next node. Until the token back to the sender node the information inside the

token will remove.

The strength of the token ring is that allows every node of the network have opportunity to

ransmit.

Fiber Distributed Data interface specifies a 100 mbps token-passing, dual ring LAN using fiber

able. It is frequently used as high-speed backbone technology because of its support for high

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bandwidth and greater distances than copper. It can be use for long distance.

2) Media access control it specified the access method for each LAN. Logical Link Control

in the data link layer. It provides single data link control protocol for all IEEE LANs. A

single LLC protocol can provide interconnectivity between different LANs because it make

the MAC sub-layer transparent.

3) Media access controlled will use the CSMA/CD to avoid collisions. CSMA/CD will follow

the access rules below:-

Carrier sense All node will continuously listens for traffic on the medium to determine

when gaps between transmissions occur.

Multiple Access Nodes may be transmitting any time they detect that the network is no

traffic.

Collision detect If the collision is detected the all will be stop as soon as possible and

wait for quasi-random length of time before retransmitting.

4) A bridge is an internetworking device use to connect two separate LAN or link the

network segment. It will filter information between them as well as traffic collisions andother network problem. A switch is a network centralized point for the network

communication, media connections and management activities.

5) CSMA/CD should be disabled if using the full-duplex (each of the nodes can be transmi

and receive at the same time). CSMA/CD is enabled if the half-duplex is using, CSMA/CD

will do the collision detect. If two or more nodes transmitting data at the same time, the bi

streams from the transmitting stations will collide with each other. If this is happens, each

transmission node must capture of detecting that a collision has occurred before it finished

sending its frame. If the collision is happen transmission will be stop as soon as possible a

it will wait a quasi-random length of time before attempting to retransmit.