On Transport Layer Adaptation in Heterogeneous Wireless Data Networks

Numerous transport protocols and protocol enhancements (e.g. TCPELN, WTCP, STP, etc) have been proposed for optimal performance in different types of wireless networks. In this paper, we define “transport layer adaptation” as the behavior of the transport protocol, with the goal of obtaining best performance, when a mobile host moves across different wireless networks. While defacto assumptions have been made in related work on the ideal characteristics of such transport layer adaptation, no explicit work has been performed in either identifying the nature of adaptation required, or the granularity at which the adaptation should occur. In this paper, we argue that : (i) Transport mechanism changes are how ideal transport adaptation should be performed. Neither transport protocol nor protocol parameter change is sufficient enough for optimal performance across heterogeneous wireless networks. (ii) Transport adaptation has to be performed at a granularity finer than interface handoffs. Ideal transport adaptation should change mechanisms even when the network characteristics change within the same wireless network. We then present the design and implementation of an adaptive transport layer framework called *TP that accommodates fine-grained runtime adaptation of transport mechanisms to achieve the best performance in a given wireless network.