Abstract
The availability of a variety of communication devices o ers a choice among networks with vastly di erent characteristics. A mobile host is likely to encounter these di erent networks and no single protocol or application can be expected to perform well under all these networks. The problem of adapting to a changing network environment is further complicated by the fact that changes in network conditions are usually transparent to the applications. In order to allow automatic adaptation of applications and protocols, awareness of link conditions and network environment is required. In this paper we present a uniform mechanism based on ICMP messages for providing environmental information to all the network protocol layers. We also show how applications and protocols can adapt to changes in the environment and in particular, demonstrate dynamic ne tuning of some of the well known protocols such as UDP and TCP. Performance measurements demonstrate that our mechanism imposes very little overhead and results in better performance of protocols that can adapt to changing network conditions.