OP is referring to "Credit based flow control", which is a way to ensure a sender does not overwhelm a receiver with more data than it can handle. Usually, thi

OP is referring to "Credit based flow control", which is a way to ensure a sender does not overwhelm a receiver with more data than it can handle. Usually, this is line-rate, but if the other side is slow for whatever reason (say the consumer is not draining data), you wouldn't want the sender to continue sending data. If you also have N hosts sending data to 1 host, you would need some way of distributing the bandwidth among the N hosts. That's another scenario where the credit system comes. Think of it as an admission control for packets so as to guarantee that no packets are lost. Congestion control is a looser form of admission control that tolerates lossy networks, by retransmitting packets should they be lost.