COMPUTER NETWORK | CONGESTION CONTROL

📌Highlights: Hi friends, In this post we will discuss about congestion control, What is congestion control,capacity of subnet,how to handle congestion. 

If each node send message with maximum rate than subnet are not able to carry message and generate congestion (traffic problem).

For Example, If subnet has capacity to carry only 100 messages. But the incoming message will we more than 100 than congestion control is needed.

Subnet is not design in the term of maximum number of delivery.

Capacity of subnet depend on following parameters:

1. Bandwidth of communication channel.

2. Number of buffer in various IMP's .

3. Speed of processor in IMP's.(The processing capacity of the processor used in different IMP's in packet/sec)

Now the graph will be:

Let we understand the above figure suppose here 100 packet/sec will be the subnet capacity that means subnet can hold 100 packet/sec.If subnet will receive 100 packet/sec and it also deliver 100 packet/sec than we get ideal curve as show in the above figure. But if we increase delivery rate more than 100 packet/sec to subnet than congestion / traffic will increase and the curve will go towards down.

Suppose if subnet received 150 packet / sec , than it is possible that subnet will deliver only 60 packet / sec due to congestion / traffic.In this way we can say that if we increase packet rate more than subnet capacity than delivery rate will decrease and not proper channel utilisation done. In this case received curve is called real curve.

For handling the congestion:

1. Congestion Prevention.

2. Congestion Avoidance

3. Congestion Recovery

Congestion Prevention:

In this scheme once we remove congestion than it will never occur.

(It is just like vaccination taken by any child once in a life and it will protect whole life.)

Congestion Avoidance:

In this scheme we continuously sense the channel whether congestion occur or not through any parameter like (monitor) and remove it.

Congestion Recovery:

In this scheme recovery will done after congestion occur. 

This is all about the introduction of congestion control i hope it is useful for you this part-I. In part-II we will discuss about Congestion Control Algorithms.