Modelling and design of TCP/IP based services over ADSL and ATM

This paper discusses some design issues for Internet based service that use TCP (transmission control protocol) over ADSL (asymmetric digital subscriber line) and ATM (asynchronous transmission mode). Analysis of the protocol and modelling work suggest that the performance of the system is affected by various tuneable parameters (e.g. those used within TCP's sliding window algorithm) and vendors' implementations of the protocol. For instance, we have observed temporary TCP stalling for up to a few seconds. A consequence of this is that telecomms operators who deploy such services are recommended to consider the behaviour of high level protocols. A small modification to TCP is suggested for such networks, although the wider impact of such a change needs to be further assessed.