Mani Raj Paul - TCP - Congestion Control

Congestion Control

When large amount of data is fed to system which is not capable of handling it, congestion occurs. TCP controls congestion by means of Window mechanism. TCP sets a window size telling the other end how much data segment to send. TCP may use three algorithms for congestion control:
  • Additive increase, Multiplicative Decrease
  • Slow Start
  • Timeout React

Timer Management

TCP uses different types of timer to control and management various tasks:

Keep-alive timer:

  • This timer is used to check the integrity and validity of a connection.
  • When keep-alive time expires, the host sends a probe to check if the connection still exists.

Retransmission timer:

  • This timer maintains stateful session of data sent.
  • If the acknowledgement of sent data does not receive within the Retransmission time, the data segment is sent again.

Persist timer:

  • TCP session can be paused by either host by sending Window Size 0.
  • To resume the session a host needs to send Window Size with some larger value.
  • If this segment never reaches the other end, both ends may wait for each other for infinite time.
  • When the Persist timer expires, the host re-sends its window size to let the other end know.
  • Persist Timer helps avoid deadlocks in communication.

Timed-Wait:

  • After releasing a connection, either of the hosts waits for a Timed-Wait time to terminate the connection completely.
  • This is in order to make sure that the other end has received the acknowledgement of its connection termination request.
  • Timed-out can be a maximum of 240 seconds (4 minutes).

Comments

Post a Comment

Popular posts from this blog

Mani Raj Paul - DPCM

Image
For the samples that are highly correlated, when encoded by PCM technique, leave redundant information behind. To process this redundant information and to have a better output, it is a wise decision to take a predicted sampled value, assumed from its previous output and summarize them with the quantized values. Such a process is called as  Differential PCM (DPCM) technique. DPCM Transmitter The DPCM Transmitter consists of Quantizer and Predictor with two summer circuits. Following is the block diagram of DPCM transmitter. DPCM Receiver The block diagram of DPCM Receiver consists of a decoder, a predictor, and a summer circuit. Following is the diagram of DPCM Receiver. The notation of the signals is the same as the previous ones. In the absence of noise, the encoded receiver input will be the same as the encoded transmitter output. As mentioned before, the predictor assumes a value, based on the previous outputs. The input given to the decoder is...
Read more

Mani Raj Paul - Quantization

Image
Quantization The digitization of analog signals in which it involves the rounding off of the values which are approximately equal to the analog values.  sampling chooses a few points on the analog signal and then these points are joined to round off the value to a near stabilized value. Such a process is called as  Quantization . Types of Quantization There are two types of Quantization - Uniform Quantization and Non-uniform Quantization. The type of quantization in which the quantization levels are uniformly spaced is termed as a  Uniform Quantization . The type of quantization in which the quantization levels are unequal and mostly the relation between them is logarithmic, is termed as a  Non-uniform Quantization . There are two types of uniform quantization. They are Mid-Rise type and Mid-Tread type. The following figures represent the two types of uniform quantization. In this the origin lies in the middle of a raising part of the stair-case lik...
Read more