alengineeringlibrary.com) Copyright © 2004 The McGraw-Hill Companies. All rights reserved. Any use is subject to the Terms of Use as given at the website. NETWORK PROCESSORS: JUSTIFICATION 32 NETWORK PROCESSORS FUNCTIONAL BLOCKS IN NETWORKING EQUIPMENT Before we can examine alternative ways of implementing different packet-processing functions, let us take a look at the conceptual partitioning inside networking devices, as shown in Figure 2.1. Functionality can be divided by the following four major blocks: The physical layer (PHY) interface. Switch fabric. Packet processing. Host processing. The PHY Interface The PHY interface is the first conceptual layer of functionality. It is currently compacted into one inte- grated component, such as a PHY chip. It is responsible for transmitting and receiving information. The bitstream, which must be transmitted by a networking device as part of being on a network, needs to be modified from its digital binary form into an analog form that can be efficiently transmitted over the communications channel medium. This must be done whether the medium is modulated light injected onto an optical fiber, an electrical current traversing a coax cable, or an electromagnetic wave radiated over the air. Similarly, in order to be received, the arriving light, electric current, or electro- magnetic wave must have its content transformed from its analog transmission form (even when it carries digital information) back into a binary digital form that the rest of the receiver's logic can han- dle properly. networking device system Switch fabric chip Queuing Compression encryption processing PROCESSING Modification Lookup/classification functions Parsing/framing PHY layer chip Transmission medium FIGURE 2.1 The conceptual functional partitioning of a network device. Downloaded from Digital Engineering Library @ McGraw-Hill (www.digitalengineeringlibrary.com) Copyright © 2004 The McGraw-Hill Companies. All rights reserved. Any use is subject to the Terms of Use as given at the website. NETWOR