Q1//Differentiate between Error control and flow control mechanism.

Answer:

Flow control:

• Flow control is meant only for the transmission of data from sender to receiver.
• For Flow control there are two approaches : Feedback-based Flow Control and Rate-based Flow Control.
• It prevents the loss of data and avoid over running of receive buffers.
• Example of Flow Control techniques are : Stop&Wait Protocol and Sliding Window Protocol.

  Error control:

• Error control is meant for the transmission of error free data from sender to receiver.
• To detect error in data, the approaches are : Checksum, Cyclic Redundancy Check and Parity Checking.
• To correct error in data, the approaches are : Hamming code, Binary Convolution codes, Reed-Solomon code, Low-Density Parity Check codes.
• It is used to detect and correct the error occurred in the code.
• Example of Error Control techniques are : Stop&Wait ARQ and Sliding Window ARQ.

Q2//Elaborate sliding window flow control mechanism with example. Also differentiate it with stop and wait method.

Answer: Sliding window protocols are data link layer protocols for reliable and sequential delivery of data frames. The sliding window is also used in Transmission Control Protocol.

In these protocols, the sender has a buffer called the sending window and the receiver has buffer called the receiving window. The size of the sending window determines the sequence number of the outbound frames. If the sequence number of the frames is an n-bit field, then the range of sequence numbers that can be assigned is 0 to 2^𝑛−1. Consequently, the size of the sending window is 2^𝑛−1. Thus in order to accommodate a sending window size of 2^𝑛−1, a n-bit sequence number is chosen. 

Suppose that we have sender window and receiver window each of size 4. So the sequence numbering of both the windows will be 0,1,2,3,0,1,2 and so on. The following diagram shows the positions of the windows after sending the frames and receiving acknowledgments.

#Note: Download the above pic by clicking on attachment button below.

Q//If the original data to send is 10011001 11100010 00100100 10000100. How would it be possible to detect error using two dimensional error detecting technique?

Answer: 

If the original data to send is 10011001 11100010 00100100 10000100. How would it be possible to detect error using …