From: Charles Reis (creis@cs.washington.edu)
Date: Sun Oct 17 2004 - 23:53:48 PDT
Congestion Avoidance and Control
Van Jacobson, 1988
Jacobson notes the profound difficulties the early Internet had with congestion collapse, and he describes how TCP was modified to more effectively detect and respond to congestion in the network. The changes are guided by the idea of maintaining "conservation of packets" in network flows, so that senders do not continually inject more packets into an overloaded network. These mechanisms have significantly improved the Internet's robustness to congestion, including "slow-start" to quickly find an appropriate transmit rate and a more accurate estimation algorithm for timeouts and retransmissions. Notably, Jacobson's approach could be deployed incrementally, using dropped packets as signals to end hosts rather than requiring all participants to recognize new header bits or messages.
The paper does take a very theoretical approach to motivate its algorithms and mechanisms, but Jacobson seems to only partly follow through on this, as most proofs and analyses are either avoided, relegated to footnotes, or left for one of several future papers. Still, sufficient detail is given and experimental results are provided to show the effectiveness of Jacobson's changes to TCP. The success of these end-host mechanisms led to later work in gateways for improved congestion avoidance, such as the Random Early Detection paper.
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