COMPUTER NETWORK LECTURE NOTES--TCP Congestion Control

TCP Congestion Control

lDynamic routing can alleviate congestion by spreading load more evenly

lBut only effective for unbalanced loads and brief surges in traffic

lCongestion can only be controlled by limiting total amount of data entering network

lICMP source Quench message is crude and not effective

lRSVP may help but not widely implemented

TCP Congestion Control is Difficult

lIP is connectionless and stateless, with no provision for detecting or controlling congestion

lTCP only provides end-to-end flow control

lNo cooperative, distributed algorithm to bind together various TCP entities

TCP Flow and Congestion Control

lThe rate at which a TCP entity can transmit is determined by rate of incoming ACKs to previous segments with new credit

lRate of Ack arrival determined by round-trip path between source and destination

lBottleneck may be destination or internet

lSender cannot tell which

lOnly the internet bottleneck can be due to congestion

TCP Segment Pacing

TCP Flow and Congestion Control