Agent-based rate coordination between TCP and ABR congestion control algorithms

✍ Scribed by K. Djemame; M. Kara

• Publisher: Elsevier Science
• Year: 2001
• Tongue: English
• Weight: 184 KB
• Volume: 24
• Category: Article
• ISSN: 0140-3664
• DOI: 10.1016/s0140-3664(00)00357-1

✦ Synopsis

In this paper we study the extent of negative interactions between Transmission Control Protocol (TCP) and Asynchronous Transfer Mode (ATM) congestion control through the application of an approach based on coordination via explicit cooperation. To do so, we implement an agent that bridges the gap between the ATM layer and the TCP layer in the protocol stack at the sender end to coordinate the congestion control algorithms of the TCP transport protocol and the ATM cell-oriented switching architecture. The novel idea uses ATM rate-based ¯ow control to adjust the credit-based window size of TCP via the implementation of the agent.

The effects of running TCP over Available Bit Rate (ABR) are studied with the help of two simulation models (LAN and WAN). Firstly, we show that TCP window (CWND) and ABR Actual Cell Rate (ACR) are weakly correlated. Secondly, we derive an Agent-based algorithm to ensure that even when the ATM switch queues are indicating no congestion, it is the switch (and not the source) which should control the increment in the TCP source rates. The introduction of the agent at the edge of the network coordinates the TCP and ATM sending transmission and clearly demonstrates a strong correlation coef®cient between CWND and ACR. The simulation results show that coordination at the edge of the network makes better use of available bandwidth and improves TCP's performance over ATM for a range of performance metrics such as Cell Loss Ratio, Packet Retransmission Ratio and Throughput.