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Journal of Information Science and Engineering, Vol.18 No.5, pp.837-847 (September 2002)

Toward Ensuring Fair Service Among ECN and non ECN
TCP Connections Over the Internet

Salahuddin Muhammad Salim Zabir+, Ahmed Ashir*, Gen Kitagata+,
Takuo Suganuma+* and Norio Shiratori+*

+Research Institute of Electrical Communication
Tohoku University
Sendai, Japan
*GN R&D Project, TAO
Tohoku University Office
Sendai, Japan

Providing fair service among TCP connections over the Internet without hampering resource utilization has recently become a major performance concern. With the rapid expansion of the Internet along with its increasingly diversified client base, the demand for a reasonably fair service is getting even stronger. To meet these requirements, congestion sensing is essential. Explicit Congestion Notification, ECN has been proved to provide a fast indication of incipient congestion and thus better the performance of a TCP/IP network. In our previous works we have proposed a strategy for ECN called Fair In-time Marking, FIM, and observed its superiority over other ECN schemes in terms of assuring a fair service. However, all TCP connections are not ECN capable. Therefore, they use packet drops for congestion signaling. In this work, we carry out investigations on gateway or router performance in providing fairness when both FIM ECN capable and non ECN capable connections are employed. We propose a new packet dropping scheme named Fair In-time Dropping, (FID) which drops packets from a connection upon detecting an incipient indication of congestion depending on its share of buffer occupancy. We also show that the combination of FIM and FID offers the best fairness compared with combining FIM with other dropping schemes.

Keywords: fairness, congestion signaling, ECN, packet dropping, drop tail, drop front, fair in-time dropping

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Received September 14, 2001; accepted April 15, 2002.
Communicated by Jang-Ping Sheu, Makato Takizawa and Myongsoon Park.