ased classifier and a CAM for layer- 7-based cookie detection and load balancing. (Source: Solidum) So does it make sense to combine a CAM with a PSM-based classifier? The answer is yes in cases where the policy rules must be changed often and in a dynamic fashion. The CAM is then used to store the lookup keys instead of SRAM. Misha Nossik presents a very elegant implementation of a web load balancer based on intelligent switching decisions made based on real-time cookie detection and URL resource management. 29 Figure 13.9 illustrates the scheme. A packet comes in through the Media Access Control (MAC)/framer and is immediately dispatched to the network processor. In the meantime, the classi- fier snoops the packet data, parses the packet content, and finds matches on-the-fly. For example, if the classifier in this application example detects the presence of a Hypertext Transfer Protocol (HTTP) GET request that a client issues to a server (with or without a cookie), it will extract the IP addresses and port numbers from the packet and produce the digest that serves as the search key when presented to the CAM. Part of Tag 1 is used as a learn mechanism by the CAM. When confronted with another subsequent packet from the same session, the CAM will be able to produce a match very fast if it sees the same session that produced Tag 1. The combination of consecutive tags (Tag 1 and Tag 2) can be used by the network processor to decide what to do with each individual packet. The drawing shows some configurable logic (field-programmable gate array [FPGA] or programmable logic device [PLD]) combining the two tags between the CAM and the bus. This is because depending on the choice of NPU bus and the precise CAM interface requirements, it may not be as straightforward for the systems designer to connect the two parts of the digest (the digest part and the command part) to the bus without any glue logic. Another interesting question would be why CAMs and PSM-based classification processors are not integrated into one chip a