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Network "plumbing" like routers and switches place unusual demands on processors, hence the rise of the network processor. Here's a snapshot of the state of the NPU art, outlining what makes a network processor and what features are likely to become most popular.
Network processors have gone from being overhyped harbingers of a networked world, to an ignored and dying technology, to a solid and thriving business. As the communications recovery continues apace, network WK processors have found a place as an important tool for any networking-equipment designer. With shipments and design wins rising, it's a good time to take a look at this new type of processor.
What is a network processor?
Simply put, a network processor is a programmable microprocessor optimized for processing network data packets. Specifically, it's designed to handle the tasks commonly associated with the upper layers of the seven-layer OSI networking model shown in Table 1: header parsing, pattern matching, bit-field manipulation, table look-ups, packet modification, and data movement. Many independent packets will be available, providing opportunities for parallel processing. Data rates for network processors range from 1.2Gbps (dual OC-12 data rate) to 40Gbps.
Software programmability is an important characteristic of network processors, because it provides flexibility across a range of applications. Even though all network processors are programmable, by definition, not all of them can be programmed by the user. Some vendors restrict access to the underlying instruction set and architecture of their network processing unit (NPU), preferring instead to do all the programming inhouse.
Not a network processor
Many chips are communications processors but not network processors. Communications processors, such as Freescale's PowerQUICC chips, are closely related to network processors but serve applications with lower data rates. Data rates for communications processors range from a few megabits per second to IGbps (for instance a single gigabit Ethernet channel). Although this dividing line may seem arbitrary and will certainly change over time, there are some other important, if subtle, differences between these two types of processors.
Communications processors cost less. Their lower prices mean they have more integration than most network processors. For example, communications processors typically contain a RISC processor core that runs a standard MIPS, PowerPC, or ARM instruction set. By contrast, most NPUs don't...