Variable Packet Size Equation Based Congestion Control

TitleVariable Packet Size Equation Based Congestion Control
Publication TypeTechnical Report
Year of Publication2000
AuthorsVasallo, P. Reviriego
Other Numbers1183

This report, extends previous work in equation-based congestion control for unicast traffic. Most best effort traffic on the internet is appropriately served by TCP which is the dominant transport protocol on the internet. However, there is a growing number of multimedia application for which TCP is not well suited. For those applications, several congestion control mechanisms have been proposed in order to avoid congestion collapse on the internet. One of them is the recently proposed TCP Friendly Rate Control Protocol (TFRC). It can be only used by flows that have a constant packet size. In this paper, we propose an extension to the TFRC protocol in order to support variable packet size flows. Variable packet size has been used for the transmission of video over the internet and is also used in voice applications. So it is important for a congestion control protocol to support variable packet size flows.We also explore the concept of fairness among flows when some of the flows send small packets. Currently, these flows are penalized by TFRC because it imitates TCP's behavior giving less throughput to flows that use small packets. We argue that if a flow is sending small packets because the application requires it to do so (for example to minimize delay in a voice over IP conversation) it should get the same amount of bandwidth as a TCP session using large packets. This results in a modified concept of TCP friendliness that we introduce in this paper.Finally we analyze some shortcomings of the equation used by TFRC to model TCP behavior and show that the impact of TCP timeouts are not completely modeled by the current TFRC equation.

Bibliographic Notes

ICSI Technical Report TR-00-008

Abbreviated Authors

P. Reviriego

ICSI Research Group

Networking and Security

ICSI Publication Type

Technical Report