TABLE OF CONTENTS Once a day a cheap, gaudy packet arrived upward from St. Louis, and another downward from Keokuk. Before these events, the day was glorious with expectancy
Mark Twain, Life on the Mississippi
Now your design builds without errors. If you could only throw a packet at it and see what happens. This chapter is for the test engineer. However, programmers may also want to run a few packets through just to make sure the design is not totally broken. In this chapter, you learn how to configure and generate packets for your simulation. You select protocols, build protocol-specific packet flows, choose distribution algorithm and rates for aggregates of flows, and attach flow aggregates to ports on the IXP2XXX network processors. In the next chapter, you run the simulation with your packets and your IPV4 router.
The Developer Workbench has a PacketSim module that feeds bytes through MAC Device Simulators to the simulator. A network traffic simulator (NTS) is a dynamic-link library that generates packets and sends them byte-by-byte to the PacketSim interface or receives packets from the PacketSim interface and validates them. There are many ways to generate packets for simulation:
From a file. The NTS can read a file defining the packets. The file can be a standard sniffer or other file format. To achieve a continual stream of packets, the NTS can repeat the set of packets. Danger: don't try this with packets that have sequence numbers. Early packet generators for IXP2XXX...
