Since network processors are very different from general purpose processors, the most important question for programmers is, how do you program it? How do you make effective use of multiple RISC cores and hardware acceleration units? Every network processor vendor insists that their design is the easiest to program, so it is good to think critically about this question.
In many ways, network processor architectures look like the parallel processing architectures of a decade ago. Programmers have tried to harness the power of parallel processing architectures for a long time, but with little luck. Vector-processing supercomputers are used for special purpose applications like weather simulation, but programmers have not been successful in using them for general purpose applications.
Is there any reason to think network processors will fare better? Yes, there is. Network processors are not trying to speed up general purpose processing. Network processing has certain characteristics that are very different from general purpose processing. Network processing involves less code but more data than general purpose processing. There is less interdependency between the data. Consider a router again. If a router receives n packets, for a small number n, it can process those packets independently. Another way of saying this is that processing these packets doesn't change the router's state. The exception to this would be configuration packets, or routing protocol packets. However, even these interdependencies are rather loose. If a router receives a packet that indicates it should update its routing tables, there is no reason it can't finish processing a few more packets before it does the update.
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