Embedded Systems November 2000 Vol13_12

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MARK KOHLER NP Complete The first generation of network processors is finally here. But what are they good for and how do they work? aj or semiconductor manufacturers are starting to sell a new type of integrated circuit, the network processor. Ne twork processors are programmable chips like general purpose microprocessors, but are optimized for the packet processing required in network devices. Network devices are a growing class of embedded system and include traditional Internet equipment like routers, switches, and firewalls; newer devices like Voice over IP (VoiP) b1idges, virtual private network (VPN) gateways, and quali ty of service (QOS) enforcers; and web-specific devices like caching engines, load balancers, and SSL accelerators. In this article, I will describe the processing requirements of network devi ces, how traditional designs meet those requiremen ts, how network processors aim to meet those requirements, and the architecture of a few ne twork processors in detail. Network processing requirements, part 1 Not all network devices have the same processing requirements. However, a lot of similarities exist. As an example, I will roughly describe the packet processing duties of a router and a web switch. These core, time-critical duties are also called data plane tasks. Routers are the workhorses of the Internet. A router accep ts packets from one of several network interfaces, and either drops them or ends them out through one or more of its other interfaces. Packets may traverse a dozen or more routers Embedded Systems Programming NOVEMBER 2000 45

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