Using a trace of address references, we compared the efficiency of several different hashing functions, such as cyclic redundancy checking (CRC) polynomials, Fletcher checksum, folding of address octets using the exclusive-or operation, and bit extraction from the address. Guidelines are provided for determining the size of hash mask required to achieve a specified level of performance. 1 INTRODUCTION The trend toward networks becoming larger and faster, addresses becoming larger, has impelled a need to explore alternatives for fast address recognition. This problem is actually a special case of the general problem of searching through a large data base and finding the information associated with a given key. For example, Datalink adapters on local area networks (LAN) need to recognize the multicast destination addresses of frames on the LAN. Bridges, used to interconnect two or more LANs, have to recognize the destination addresses of every frame and decide quickly whether to receive...

A new algorithm for generating order preserving minimal perfect hash functions is presented. The algorithm is probabilistic, involving generation of random graphs. It uses expected linear time and requires a linear number words to represent the hash function, and thus is optimal up to constant factors. It runs very fast in practice. Keywords: Data structures, probabilistic algorithms, analysis of algorithms, hashing, random graphs

A current research topic in the area of relational databases is the design of systems based on the Non First Normal Form (NF ) data model. One particular development, the so-called extended NF data model, even permits structured values like lists and tuples to be included as attributes in relations. It is thus well suited to represent complex objects for non-standard database applications. A DBMS which uses this model, called the Advanced Information Management Prototype, is currently being implemented at the IBM Heidelberg Scientific Center. In this paper we examine the problem of detecting and deleting duplicates within this data model. Several alternative approaches are evaluated and a new method, based on sorting complex objects, is proposed, which is both time- and space-efficient.