Integration of mobile hosts into the existing internetwork consisting mostly of stationary hosts gives rise to some peculiar problems because of the special requirements of low power mobile hosts and also because of the special characteristics of the wireless link. Several Mobile-IP proposals [9, 16, 181 have addressed the problem of delivering IP packets to mobile hosts regardless of their location. In theory one can use existing fixed network transport protocols such as UDP [I41 and TCP 1151 with one of the Mobile-IP proposals for communication between mobile hosts and the fixed network. This naive approach however, gives rise to performance problems, especially when a mobile host switches cells or is temporarily disconnected [5, 63. More seriously, all Mobile-IP proposals attempt to hide mobility, disconnection and other features of mobile wireless computing from transport and higher layers thus ruling out any specialized handling of such features. On the other hand, use of a new protocol stack for mobile hosts causes interoperability problems with the fixed network protocols. An indirect model for mobile hosts [3] allows the development and use of specialized transport protocols that address the performance issues on the comparatively low bandwidth and unreliable wireless link. Protocols developed using this model can also mitigate the effects of disconnections and moves while maintaining interoperability with fixed network protocols. This paper describes I-TCP, an indirect transport layer protocol, which allows a mobile host to communicate over a transport layer connection with the fixed network via its current Mobile Support Router (MSR). The TCP connection with the fixed host is actually established by the MSR on behalf of the mobile host (MH). If the MH moves to another cell during the lifetime of the TCP connection, the new MSR takes over the connection from the old MSR. Experiments with I-TCP on our testbed show substantial throughput improvement over regular TCP when one of the end points is mobile.
I-TCP REF is a split connection approach that introduces a transport layer intermediary for splitting a TCP connection between a fixed and a mobile host into two connections.
I-TCP: indirect TCP for mobile hosts
Proceedings of 15th International Conference on Distributed Computing Systems
Proceedings of 15th International Conference on Distributed Computing Systems
Computer Science