Copyright © 2004 John Wiley & Sons, Ltd. Published online 4 May 2004 INTERNATIONAL JOURNAL OF NETWORK MANAGEMENT Int. J. Network Mgmt 2004; 14: 241–255 (DOI: 10.1002/nem.520) A new approach to ensure fairness over the Internet By Salahuddin Muhammad Salim Zabir* † , Ahmed Ashir, Gen Kitagata and Norio Shiratori Congestion signaling is an essential issue for ensuring a high network performance. Explicit congestion notification (ECN) has been proved to provide a faster indication of congestion and thus improve the QoS of a TCP/IP network. In this paper, we present a new scheme for ECN named fair in-time marking (FIM), which employs a mechanism that as well as providing an indication of incipient congestion, assures a fair service to all the connections. To facilitate such services using FIM, we propose inclusion of some simple yet effective functionalities in the routers. This is important as the client base of the Internet is increasing rapidly and the demand for a reasonably fair service is getting stronger. Experiments show that FIM offers the best fairness, sometimes better by around 20% or more without affecting efficiency, compared with other proposed schemes for ECN. Copyright © 2004 John Wiley & Sons, Ltd. Salahuddin Muhammad Salim Zabir joined the Department of Computer Science and Engineering of Bangladesh University of Engineering and Technology in 1995. At present, he is with RIEC, Tohoku University, Japan. He is a member of IEEE, BCS and BAAS. Ahmed Ashir received his PhD in 1999 from Tohoku University, Japan. At present, he is with the Japan Gigabit Network (JGN) Project of Telecommunication Advancement Organization (TAO), Tohoku University Office. Gen Kitagata received a Dr. Eng. degree in information engineering from Tohoku University where he is working as a research associate. His research interests include agent-based computing and network middleware design. He is a member of IEICE. Norio Shiratori is a professor at the Research Institute of Electrical Communication (RIEC), Tohoku University. He has been engaged in research on distributed processing systems and flexible intelligent networks. He is a Fellow of the IEEE, IEICE, IPSJ. *Correspondence to: Salahuddin Muhammad Salim Zabir, Research Institute of Electrical Communication, Tohoku University, Japan. † Email: szabir@ieee.org Introduction L ink efficiency and fairness are two impor- tant metrics concerning network perfor- mance. While contributions to elevate link efficiency have attained reasonable success, the matter of ensuring fair service to all the con- nections still remains to be addressed adequately. Particularly in case of a router with a congested link, this is an essential concern. In this paper, we present a mechanism we name fair in-time marking (FIM) that offers both high link efficiency and fair service among TCP connections. In order to attain such performance goals in a network, proper congestion signaling is essential. In a typical window-based network traffic manage- ment scheme like TCP/IP, this is done implicitly by detecting packet drops. Algorithms generally employed for the purpose either use TCP time out or receiving duplicate acknowledgements (ACK). 1 Packet drop in either case causes TCP retransmis- sions and thus adds to the network congestion along with the extra time requirement for the whole transmission process resulting in network performance degradation. These disadvantages of sensing congestion implicitly pave the way for explicit congestion notification (ECN). The idea is to get an indication of incipient congestion explicitly before the con- gestion actually occurs and thus control traffic sources so as to avoid router or gateway buffer overflow. There are two approaches for ECN.