Content based discarding in IP-routers

There is a growing set of UDP (user datagram protocol) based applications using inadequate congestion control algorithms or none at all (i.e., the flow does not throttle back upon receipt of congestion notification). Such UDP applications include streaming applications like packet voice and video, and also multicast bulk data transfer. Congestion avoidance algorithms in routers are not able to handle these flows adequately and this leads to an unfair distribution of bandwidth among TCP and UDP flows in times of congestion. Moreover the random dropping of IP packets in times of congestion in routers causes a decreasing goodput delivered to the receiving application because whole TCP or UDP packets are discarded at the receiver when one IP packet is missed. This leads to retransmissions when using TCP and can cause serious problems with the display of a multimedia stream when using UDP. This paper proposes a method to overcome the mentioned problems by introducing an additional header into the IPv6-header (Internet Protocol Version 6 Draft Specification, 1998) to label the dependencies of several IP packets and distinguish between different flows at the IP level. A structured description of the application data contents helps to include dependencies of the application data level. The description is mapped onto several priority levels to describe the dependencies within an ADU (application data unit). This paper also explains the way to derive ADUs from the multimedia data and the benefit that can be taken from IP-labeling inside the Internet. As a technical basis, the concepts described in the paper are validated by a simulation study.