For Full-Text PDF, please login, if you are a member of IEICE,|
or go to Pay Per View on menu list, if you are a nonmember of IEICE.
Active ECN Mechanism for Fairness among TCP Sessions with Different Round Trip Times
Takahiro MATSUDA Akira NAGATA Miki YAMAMOTO
IEICE TRANSACTIONS on Communications
Publication Date: 2004/10/01
Print ISSN: 0916-8516
Type of Manuscript: PAPER
TCP, fairness, explicit congestion notification (ECN), rate control, active queue management (AQM),
Full Text: PDF(1.1MB)>>
The window flow control based end-to-end TCP congestion control may cause unfair resource allocation among multiple TCP connections with different RTTs (round trip times) at a bottleneck link. In this paper, in order to improve this unfairness, we propose the active ECN which is an ECN based active queue mechanism (AQM). A bottleneck router with the proposed mechanism marks TCP segments with a probability which depends on the RTT of each connection. By enabling the TCP senders to reduce their transmission rate when their packets are marked, the proposed mechanism can realize the same transmission rate among TCP connections with different RTTs. Furthermore, the active ECN can directly mark ACKs from TCP receivers, while the conventional ECN marks TCP segments coming from the TCP senders. As a result, the queue length distribution at the bottleneck link gets stabilized, because the sender can quickly react to the marking according to variation of the queue length.