Promote the Use of Explicit Delay Control

Abstract

The Internet is undergoing changes of its traffic mix, with the IP-based interactive multimedia applications gaining momentum. According to studies, UDP-based multimedia traffic has in recent years risen to above 25% of the overall Internet traffic volume, as compared to only 5% a decade ago. To these delay sensitive real-time interactive multimedia applications, out of delay boundary packets are usually obsolete. However the current Internet Protocol lacks a way to control the lifetime of the packets effectively. In this paper, we propose the Explicit Delay Control (EDC) as a viable packet lifetime control mechanism designed for such purpose. It uses an embedded Maximum Tolerable Delay (MTD) field in an IPv4 option. The value of MTD is determined by taking the application specific delay bound, measured round-trip-time, and the estimations of the pathpropagation delay and transmission delay into account. At each network node, the MTD is deducted by the singlehop delay. Packets that expire their lifetime are discarded and non-congestion related delay losses are signaled to the sender to reduce inaccuracy in delay estimations and to adapt to path changes. We implemented EDC in the Linux kernel. Our evaluation has shown that EDC can ensure the “legality” of the packets, reduce the waste of bandwidth and processing time in the networks, and help to alleviate congestions.