Receiver–based Management Scheme of Access Link Resources for QoS–Controllable TCP Connections

Although the bandwidth of access networks is rapidly increasing with the latest techniques such as DSL and FTTH, the access link bandwidth remains a bottleneck, especially when users activate multiple network applications simultaneously. Furthermore, since the throughput of a standard TCP connection is dependent on various network parameters, including round–trip time and packet loss ratio, the access link bandwidth is not shared among the network applications according to the user’s demands. In this thesis, we present a new management scheme of access link resources for effective utilization of the access link bandwidth and control of the TCP connection’s throughput. Our proposed scheme adjusts the total amount of the receive socket buffer assigned to TCP connections to avoid congestion at the access network, and assigns it to each TCP connection according to characteristics in consideration of QoS. The control objectives of our scheme are (1) to protect short-lived TCP connections from the bandwidth occupation by long-lived TCP connections, and (2) to differentiate the throughput of the long-lived TCP connections according to the upper-layer application’s demands. One of the obtained results from the simulation experiments is that our proposed scheme can reduce the delay of short-lived document transfer perceived by the receiver host by up to about 90% , while a high utilization of access link bandwidth is maintained.