Configure Congestion Window Minimum (CWMIN) Parameter

The CWMIN parameter is important in managing traffic flow and retransmissions under varying network conditions. Changing the congestion window by setting CWMIN to a higher value affects how long it takes to recover from the retransmit event. This limits how far the window gets closed in a retransmit-event condition. In the extreme case, one could set CWMIN to the configured buffer size, which allows the entire buffer bandwidth to be used. As a general rule, setting CWMIN to a value equal to half of the traffic rate in an RTT interval should allow adequate retransmit-recovery time while preventing excessive load to the peer.

CWMIN = (Bytes/Sec * RTT) / 2 bytes

Note:

Setting CWMIN to a value much higher than MTU will result in periodic intermediate node overloads. CWMIN can’t be set less than 3K and should not exceed the remote peer reception window (Advertized Reception window). When possible CWMIN is normally set to ~64K or greater. The specific value chosen for the sender should take into account network latency, configuration, packet loss, capacity, and traffic characteristics. It is important that RMIN be set to a value greater than the expected average RTT to minimize false retransmissions. CWMIN could be set to a value between 10% and 20% of the remote peer Reception window.