This event handles the timeout of frame f which was sent to dst. The units of time in the simulation should be msec. To simplify the simulation and since you know the number of frames that you will be simulating, there is no need to have sequence numbers that wrap around. Therefore unique ids for each frame for a particular destination can be used. Ignore the processing time at the source and destinations.
Error detection is used and is assumed to work.
Acknowledgements can be transmitted as soon as a frame arrives without error. There is no need to queue the acknowledgements since this is the only traffic on the return link. Assume the acknowledgement is the same size as the frame and the return link to a destination has the same error probability, bit rate and propagation delay as the forward link. The parameters are the input to the simulation program. Assume the same timeout value for all frames.