So you now know a lot (perhaps more than you wanted to!) about the IXP2XXX hardware, but how do you program this hardware? First and foremost, you have to pick a programming model appropriate for your application. A programming model guides your decisions about how and why you use each of the various pieces of the IXP2XXX hardware. Selecting the appropriate programming model involves deciding how to make good use of the available hardware resources, whereas an inappropriate programming model can make development seem like running up hill into a head wind. The first part of this chapter discusses how to think about your application and the different programming models that have proven effective on the IXP2XXX processor.

Once you have selected a model, you probably don t want to start from scratch developing tools and libraries for basic access to the hardware and support for your model. Instead, you ll want to build your application using existing tools and libraries. Fortunately, a programming environment for working with the IXP2XXX processor, called the IXA SDK version 3.0, is available. This SDK includes tools, a framework supporting several effective IXP2XXX programming models, and libraries for developing code. We ll also cover the IXA SDK 3.0 in this chapter so you will have a general understanding of it and its application.