CRC32 Based Signature Generation Methods for URL Routing

Abstract

Signature algorithms have already been proposed for use in URL routers. Cyclic Redundancy Check (CRC) codes can be used as URL signatures. When a packet is received, CRCs are generated on the fly with the use of very simple hardware circuits. Existing network adapters are not programmed to generate CRCs on packet subfields. However, it is possible to use the CRC circuit of a network adapter to simultaneously generate the packet CRC and CRCs on any subfield (such as the URL string in the HTTP GET request header) of the packet. The intermediate CRC codes (available from the CRC circuit) can then be used to produce a URL signature for each incoming HTTP request and do URL routing table look-up. In this paper we evaluate alternatives for URL signature generation that rely on hardware or software computation of CRC32 codes. Our results indicate that the delay of producing the signature in software is smaller (100s of nanoseconds) as compared to the alternative of using the CRC circuit in existing adapters (10s of microseconds).