Isarithmic Congestion Control

The algorithm is called Isarithmic because the tidal number of packets in the network is kept constant by issuing "permits", circulate in the subnet. To transfer data, and IMP must capture a "permit", destroy it and transfer the data to the destination IMP and destination IMP on reception of the data regenerates the "permit". By this method the congestion can never arise, in the subnet as a whole.

However it has a few drawbacks,

• It does not guarantee that a given IMP will never be flooded with packets.
• Permits must be uniformly distributed to prevent long delays by some IMPs. It is preferred to have them centralized.
• If a permit is destroyed for some reason, they are lost forever and the network capacity is reduced.