Abstract: The invention provides a method and system for lookup of message header information that has the advantages of low-power, speed, and flexibility. The invention uses a sequence of pipelined on-chip memories, each having only a portion of the header information intended for lookup. Each one of the on-chip memories simultaneously performs a lookup on a portion of the header information, allowing embodiments of the invention to operate on multiple messages worth of header information substantially simultaneously. The invention uses a novel data structure for recording destination addresses in the sequence of on-chip memories, having the property that moving information about destination addresses, or otherwise responding to changes in network topology is flexible, while at the same time maintaining relatively dense usage of the on-chip memories.

Abstract: A new process called “crossproducting” allows level 4 switching to be performed at gigabit speeds. In crossproducting, a database of routing filters or rules is “sliced” into columns corresponding to fields. Each column represents a set of prefixes or ranges. Given a data packet P, a best matching prefix or narrowest enclosing range lookup is performed separately for each packet field. The results of the lookups on individual fields are concatenated to quickly determine the earliest matching rule. The search can be optimized further through such techniques as removing default entries, creating multiple crossproduct tables, caching crossproducts, and early stopping, the latter optimization being made possible by recognizing that it is not necessary in all cases to search all columns for a match. The inventive devices and methods are applicable to various types of networks, including, but not limited to, the Internet and related types of networks, and telephone switching networks.

Abstract: The preferred embodiments described herein provide a Packet Matching System and Method. A Matching Rules Database is quickly searched for a Best Matching Rule for a packet header. Power is conserved in the system by searching only a small subset of rules of the rules database. An All Matching Rules Engine comprising a plurality of Necessary Path Condition Rules is searched to determine which subset of matching rules, or sub-databases, to search for a best matching rule. The sub-databases are then searched by Best Matching Rules sub-Engines and a best matching rule is selected from the results of the sub-database searches by a Collate Engine. The Rules Database is organized according to a Hierarchical Subdivision Tree. Necessary Path Condition Rules and sub-databases are extracted from the Hierarchical Subdivision Tree.

Abstract: A method for compressing a routing table involves constructing a binary tree representation of the routing table. The compression method makes three passes through the tree. In a first pass, the compression method propagates routing information down to the tree leaves. During this pass, the program assigns every leaf node in the tree an associated next hop or an inherited next hop from a higher level ancestral node. In a second pass, the compression method migrates prevalent next hops up the tree. This bottom up pass involves forming a set of next hops at a parent node by supernetting the sets of next hops A and B for a pair of child nodes corresponding to the parent node, according to the following operation: A*B=A∪B, if A∩B=&phgr; A∩B, if A∩B≠&phgr; where A*B is a set of next hops formed at the parent node. In the third pass, the compression method eliminates redundant branches in the tree.

Abstract: Fast, scalable methods and devices are provided for layer four switching in a router as might be found in the Internet. In a first method, a grid of tries, which are binary branching trees, is constructed from the set of routing filters. The grid includes a dest-trie and a number of source tries. To avoid memory blowup, each filter is stored in exactly one trie. The tries are traversed to find the lowest cost routing. Switch pointers are used to improve the search cost. In an extension of this method, hash tables may be constructed that point to grid-of-tries structures. The hash tables may be used to handle combinations of port fields and protocol fields. Another method is based on hashing, in which searches for lowest cost matching filters take place in bit length tuple space. Rectangle searching with precomputation and markers are used to eliminate a whole column of tuple space when a match occurs, and to eliminate the rest of a row when no match is found.

Abstract: Many network protocols, including the Internet, have addresses that are structured hierarchically. The hierarchy is expressed by an address prefix P that represents all addresses in the given hierarchical level that starts with prefix P. The hierarchy is not strict and can be overridden by more inclusive hierarchies. This is achieved by having network routers find the longest prefix that matches a destination address in a message.The disclosed invention describes a method and apparatus for implementing controlled expansion: for expanding a set of prefixes into an equivalent (possibly larger) set of prefixes that have a smaller set of prefix lengths. The new set of prefixes can then be looked up significantly faster using any technique whose speed improves by reducing the number of prefix lengths. Our invention also incorporates fast techniques to insert and delete new prefixes, and a technique of pointer hoisting to halve the memory READs needed for trie search.