flow control and error control in data link layer Ozark Missouri

Address 1111 S Glenstone Ave, Springfield, MO 65804
Phone (417) 429-1735
Website Link

flow control and error control in data link layer Ozark, Missouri

The fact that there are two different mechanisms of error detection/correction is because they operate at different layes of the model so every group in charge implements their own techniques to But if the channel is busy, the station does not continuously sense it but instead of that it waits for random amount of time and repeats the algorithm. Sequence Numbers • Frames from a sender are numbered sequentially. • We need to set a limit since we need to include the sequence number of each frame in the header. Two types of error correction are used commonly: ARQ (Automatic Repeat reQuest) and FEC (Forward Error Correction).

Redundancy is the concept of using extra bits for use in error detection. Flow and Error Control Prof. The system returned: (22) Invalid argument The remote host or network may be down. Control Variables • Sender has 3 variables: S, SF, and SL • S holds the sequence number of recently sent frame • SF holds the sequence number of the first frame

This action is taken whether it is not expected by the network layer. Previous protocols have only the flow of one sided, means only sender sends the data and receiver just acknowledge it, so the twice bandwidth is used. If sender is sending too fast the receiver may be overloaded, (swamped) and data may be lost. What if the speed (hardware/software) of the sender or receiver differs?

Cumulative vs. If it detects the medium busy, it waits for the channel to become idle. See control field for unnumbered frames in HDLC ppt file. The sender in this case, sends only packet for which NACK is received.

Connectionless: could be acknowledged or unacknowledged. Several protocols are developed for improving the performance. Recommended Matting, Framing, and Hanging Your Photographs Flow & Error Control tameemyousaf Error Detection And Correction Renu Kewalramani Flow Control selvakumar_b1985 Data link layer V R Siddhartha Engineering College Data Link Piggybacking • A method to combine a data frame with ACK. • Station A and B both have data to send. • Instead of sending separately, station A sends a data

The system returned: (22) Invalid argument The remote host or network may be down. CSMA/CA CSMA/CA is Carrier Sense Multiple Access/Collision Avoidance. Accepts as the 1st frame in the next cycle-an error 21. A Protocol Using Selective Repeat Protocol using Go back N is good when the errors are rare, but if the line is poor, it wastes a lot of bandwidth on retransmitted

If the station waits for the medium to become idle it is called persistent otherwise it is called non persistent. TCP. • The window slides to include new unsent frames when the correct 14. Therefore it discards the second copy of frame 1. 8. Checksum checker Receiver receives the data unit and divides into segments of equal size of segments.

Acknowledgement • Receiver sends positive ACK if a frame arrived safe and in order. • If the frames are damaged/out of order, receiver is silent and discard all subsequent frames until Mac Layer is one of the sublayers that makeup the datalink layer of the OSI reference Model. In Communication, there is communication medium between sender and receiver. This type of scheme is called Positive Acknowledgment with Retransmission (PAR).

In ALOHA Collision probability is quite high. This is the maximum number of frames that the receiver is willing to receive. Burst error is also called packet level error, where errors like packet loss, duplication, reordering. On a noisy transmission medium a successful transmission could take a long time, or even never occur.

Pipelining effect occurs improving the efficiency of the protocol. This is known as exponential back off. In Selective Repeat ARQ, only the damaged frame is resent. A Protocol Using Go Back N The problem with pipelining is if sender sending 10 packets, but the problem occurs in 8th one than it is needed to resend whole data.

This problem is explained more specifically below. Receiver is waiting for frame 0 in part a. 15. Final data unit is 10001010 00100011 01010000. This four intervals are shown in the figure given below.

slot) and returns to Step 2 After 10th retry, random number stops at 1023. no. This type is not so much efficient, but it is simplest way of Flow Control. So when the timer expires, the sender retransmits the original frames, 0 to 6 to the receiver.

Basic idea of this mechanism is a user can transmit the data whenever they want. Unnumbered frames must be allowed to carry data in addition to carrying SABM (Set ABM mode - open connection), SABME (E: Extended - control field is 16 bits and sequence numbers In the following sections data link layer's functions- Error control and Flow control has been discussed. iii.