Question

(2 Marks) (a) Specify the basic functions of the link layer. (b) Compute the CRC (cyclic redundancy code) for the data 10110110 using the generator 1011. 1. (3 Marks)

Answer 1

. The basic functions of it are as follows:-

1)Framing - the data link layer divides the stream of bits received from the network layer into manageable data units called frames.

2)Physical addressing - If frames are to be distributed to different systems on the network , the data link layer adds a header to the frame to define the sender or receiver of the frame.

3)Flow control - If the rate at which the data are absorbed by the receiver is less than the rate at which data are produced in the sender , the data link layer imposes a flow control mechanism to avoid overwhelming the receiver .

4)Error control - The data link layer adds reliability to the physical layer by adding mechanisms to detect and retransmit damaged or lost frames .

5)Accsess control - When two or more devices are connected to the same link , data link layer protocols are necessary to determine which device has control over the link at any given time .

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