their operation. Some conservative system builders already require that the network processing unit (NPU) they choose must be able to economically support the equivalent of 2M lookup table entries in order to handle the short- to medium-term evolution of these needs. From this context, we can imagine where this trend will lead us within the next 5 to 10 years when it comes down to compiling life-span requirements for network-processing and lookup circuitry capabilities inside new carrier-grade equipment for which ongoing investment will ultimately be contemplated. This is why in the previous chapter we alluded to the importance of properly managing the con- tent of TCAMs by reshuffling entries SO that entries are arranged in the order of decreasing prefixes and that no empty space exists between entries. This actually leads to the fortunate situation where if properly ordered, the entries are structured in blocks, starting first with the 32-bit-long prefixes, then the block with the 31-bit-long prefixes, then the block with the 30-bit-long prefixes, and SO on. The mere order of these blocks significantly accelerates the search time. By finding a match and knowing which prefix block was obtained, the length of the prefix can be determined, SO half of the problem has already been tackled. 4. See http://bgp.potaroo.net. 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. CLASSIFICATION PROCESSORS 244 NETWORK PROCESSORS The continuous arrangement of entries (deleting old entries, inserting new entries, and moving blocks of entries to accommodate dynamic updates) in such a way is a frequent problem and sub- stantial research is being carried out. ALGORITHMS FOR MANAGING LOOKUP TABLE UPDATES It is foolish to think that every time a new entry must be suddenly inserted somewhere (at the right prefix block) into the TCAM-based lookup and forwarding table