The traffic simulator, sim which was written by Simon Crosby and modified by Steve Pope, can produce traces which are representative of real traffic. The usage of this tools is as:
sim [-s seed] [stoptime (ms)] [ports ssvs tcps tcp_res]
Where ports should be set to zero, ssvs represents a number of silence suppressed voice sources, tcp a number of tcp sources.
Two other utility programs have also been written to generate traces to augment the above traffic simulator. The program Bernoulli generates a trace file containing traffic which obeys a Bernoulli distribution for cell inter-arrival time. The parameters of the Bernoulli distribution are supplied as arguments to the program. These specify the ``load'' placed on the link by the Bernoulli traffic.
The program mktrace takes as argument a file name. Optionally it takes an argument which indicates the processing to be performed on the file. If the argument ``-o'' is given, processing assumes that the supplied file contains a traffic trace of the form described in the sections above. In this case the traffic trace is interpreted and output data in the form of an inter-arrival time series for cells is printed on the standard output. This permits a trace of the source behaviour (theoretical, of course) to be generated for comparison with observed data.
If no optional argument is given to the program then processing assumes that the supplied file has the following format: each line begins a new entry. Each entry consists of two integers. The first is a count of the number of idle slots before a block is sent, and the second is a block count which is the number of back-to-back cells to be sent in the block. This permits easy encoding of the contents of a simple cell trace with only one vci.
Note that the Transmission line speed (100 Mbits/sec) and the Fairisle fabric speed (dependent on fabric clock) are normally not the same. When generating trace files, different traces should be generated to take account of this difference.
The first line of a traces file always contains the number of trace entries in that file. Subsequent entries in the file are an integer representation of the 32 bit binary number:
