The presence of congestion means the load is greater than the resources available over a network to handle. Generally we will get an idea to reduce the congestion by trying to increase the resources or decrease the load, but it is not that much of a good idea.
There are some approaches for congestion control over a network which are usually applied on different time scales to either prevent congestion or react to it once it has occurred.
Now let us see one of the techniques for congestion control which is termed as load shedding −
It is one of the approaches to congestion control. Router contains a buffer to store packets and route it to destination. When the buffer is full, it simply discards some packets. It chooses the packet to be discarded based on the strategy implemented in the data link layer. This is called load shedding
Load shedding will use dropping the old packets than new to avoid congestion. Dropping packets that are part of the difference is preferable because a future packet depends on full frame.
To implement an intelligent discard policy, applications must mark their packets to indicate to the network how important they are. When packets have to be discarded, routers can first drop packets from the least important class, then the next most important class, and so on.
The advantages of load shedding are given below −
It can be used in detection of congestion.
It can recover from congestion.
It reduces the network traffic flow.
Synchronised flow of packets across a network.
Removes the packets before congestion occurs.
The disadvantages of load shedding are given below −
Packets get lost because of discarding by the router.
If buffer size is less it results in more packets to get discarded.
Cannot ensure congestion avoidance.
Overhead for the router to always keep on checking whether the buffer is full.