Advisor: Professor Raj Jain.

The problem of traffic management has been widely recognized as critical to the development of an operational Internet. The goal of traffic management is to efficiently allocate network resources including buffers and bandwidth, and provide the negotiated QoS guarantees to users. This thesis studies the problem of traffic management for the Transmission Control Protocol/Internet Protocol (TCP/IP) suite over Asynchronous Transfer Mode (ATM) networks. The ATM Unspecified Bit Rate (UBR), Guaranteed Frame Rate (GFR) and Available Bit Rate (ABR) service categories are intended for data applications. The main focus of this research is to analyze and improve the performance of TCP over UBR, GFR and ABR.

This thesis proposes buffer management algorithms for the UBR and GFR services, and a feedback control algorithm for the ABR service. A buffer management scheme called Selective Drop is presented for the UBR service. An analysis of the relative performance of three TCP flavors -- slow start and congestion avoidance (Vanilla), fast retransmit and recovery (Reno), and selective acknowledgments (SACK), with three buffer management policies -- Tail Drop, Early Packet Discard (EPD), and Selective Drop, is then presented for LAN, WAN and satellite networks.

The results show that for LANs, TCP performance over UBR can be improved by using intelligent buffer management policies. As the propagation delay increases, the TCP policies become more significant than buffer management -- SACK performs the best while Reno performs the worst. In the presence of high priority variable bit rate traffic, guaranteed rate can be provided to the UBR service to prevent bandwidth starvation.

This research proposes the Differential Fair Buffer Allocation (DFBA) scheme for the GFR service. DFBA provides minimum rate guarantees to VCs carrying TCP traffic by allocating buffers in proportion to the guaranteed rates and probabilistically dropping packets.

Finally, the thesis proposes a virtual source virtual destination scheme for ABR that can be used to limit the buffer requirements of terrestrial networks connected to long delay satellite networks.

The experiments and analysis in this research provide valuable insight into designing traffic management solutions for broadband networks.

Complete paper in Adobe Acrobat 3.0 Format (2,492,442 bytes) |