Congestion Control in Computer Networks

Congestion Control

Congestion causes choking of the communication channel. When too many packets are displayed in a part of the subnet, the subnet's performance degrades. Hence, the network's communication channel is called congested if packets are traversing the path experience primarily over the path propagation delay.

It is known as heavily congested when the packets never reach the destination, denoting the delay method infinity. When the input traffic rate exceeds the output lines capacity, the subnet's input part gets choked and generates congestion. It also happens when the routers are too slow to execute queuing buffers, refreshing tables, etc. The loss of capacity of the routers' buffer is also one of the many factors for congestion. However, enhancing the memory of the router may be helpful up to a certain point.

Principles of Congestion Control

As per control theory, the computer network, which is also a system, is divided into two groups. They are open-loop and closed-loop solutions.

The Open-loop Solutions

It provides an excellent design to ensure that the problem does not occur in the first place. The designing tools include deciding to accept new traffic, discarding packets and scheduling the packets at various network points. The open-loop solution's decisions are independent of the current state of the network.

Closed-loop solutions

It makes the decision based on the concept of a feedback loop. The feedback Notes loop enables the closed-loop system to monitor the procedure to detect when and where congestion occurs. After that, it passes the information to the places where they can take actions.

The system's monitoring depends on the percentage of all packets discarded for drawback of buffer area, the average queue lengths, the multiple packets that time out and are retransmitted, the normal packet delay and the standard deviation of packet delay.

Secondly, hosts or routers share packets periodically to directly know about congestion so that the traffic around congested areas can be routed to alternate destination routes.

The congestion can be controlled as given below:

• It can raise the bandwidth in the network. It can be increased if an additional line temporarily increases the bandwidth between specific points.
• It is used to split traffic to follow multiple routes.
• It can increase the resources. For example, use spare routers.
• It is used to decrease the load by denying service to some users or degrading service to some or all users.
• It is used to estimate users' schedule and demands in a more predictable way.