On the transition to a low latency TCP/IP Internet

Recently, a number of active queue management (AQM) algorithms, such as REM (random exponential marking) and GREEN, have been proposed which reduce the packet queueing backlog and hence reduce the network\´s latency to close to the propagation delay. This paper uncovers a fundamental problem that a low latency TCP/IP network faces. We call this problem "low latency efficiency collapse". With explicit congestion notification (ECN) still not widely deployed, the main congestion notification remains packet dropping. By reducing the round trip time (RTT) to near the propagation delay, TCP sessions become very aggressive and the packet dropping rate required for congestion notification becomes prohibitively high. A solution to this problem is introduced. It is based on inducing latency. When applied to the new AQMs, it limits the packet loss whilst the Internet makes the transition to ECN. We demonstrate by an experiment that the proposed solution improves the efficiency by about 20%.