CLAMP: Maximizing the Performance of TCP over Low Bandwidth Variable Rate Access Links

This paper presents CLAMP, a distributed algorithm to enhance the performance of TCP connections that terminate in a wireless access network. CLAMP works at a receiver to control a TCP sender by setting the TCP receiver’s advertised window limit. Coupled with existing TCP sender side implementations and active queue management, CLAMP provides a complete end-to-end flow control scheme optimised for wireless access networks. CLAMP provides explicit control over wireless link utilisation and queueing delay, and allows a controlled proportion of the link capacity to be allocated to each flow sharing the same radio bearer. The only information required from the access network is the aggregate bottleneck queue size; specifically, it does not rely on propagation delay estimates. No modifications are required to the sender side or the core network. The performance of CLAMP is investigated under a range of network conditions and conditions for convergence are found.