Question

Difference between open loop and closed loop congestion control

Answer 1

In the open loop congestion control policies are made in such a way that congestion is avoided before it occurs . This type of congestion control can be control by the source as well by the destination. The methods by which open loop is used includes the  window policy, retransmission policy etc.

on the other hand closed loop congestion control is used to  throw out the congestion  after the congestion is made or occur. it uses method of back pressure and choke packet etc. 

Answer 2

Open loop congestion control helps to prevent congestion. In other words, it does not allow congestion to take place at all. This type of congestion control does not require end-to-end feedback.

Closed loop congestion control helps in removing congestion after it has occurred. This congestion control adjusts the cell-rate based on feedback received.