Ad hoc networks are completely wireless networks of mobile hosts, in which the topology rapidly changes due to the movement of mobile hosts. This frequent topology change may lead to sudden packet losses and delays. Transport protocols like TCP, which have been designed for reliable fixed networks, misinterpret this packet loss as congestion and invoke congestion control, leading to unnecessary retransmissions and loss of throughput. To overcome this problem, a feedback scheme is proposed so that the source can distinguish between a route failure and network congestion. When a route is disrupted, the source is sent a Route Failure Notification packet, allowing it to invalidate its timers and stop sending packets. When the route is reestablished, the source is informed through a Route Reestablishment Notification packet, upon which it resumes packet transmissions. Simulation experiments show that in the event of route failures, as the route reestablishment time increases, the use of feedback provides significant improvements in performance.

. Multimedia CSCW applications are rapidly becoming mainstream business tools. If users are to be able to perform useful tasks with these tools the acceptability of the subjective quality of the service must be adequate. This acceptability is affected by many factors, including the user interface, the task undertaken, the audio and video coding, the connection speed and the network performance. The end-to-end delay has been identified as a significant parameter affecting the user's satisfaction with the service. Earlier work identified the delay bounds for which the quality of the CSCW service was acceptable to users performing real tasks. These limits formed the basis for an investigation to identify which system components contribute most to this delay. The components contributing to the delay of audio and video have been measured and the major sources identified. 1 Introduction Although initially targeted at home users, multimedia products are now increasingly being use...