A DNS-based Client Redirector for the Apache HTTP Server

Michal Szymaniak

June 2002

Abstract:

The client redirection problem is one of the most fundamental issues when developing a Content Delivery Network (CDN). This thesis discusses three known solutions and describes the implementation of one of them, which exploits a special DNS protocol implementation. The system consists of a special module for the Apache HTTP Server, which supports the basic functions of a typical DNS server. The module generates custom DNS responses based on network distance calculations according to the AS-path length metric. The Internet topology information required to compute the AS-path length metric is derived from BGP routing tables. Performance measurements prove that the overhead introduced by the network distance calculations is negligible in comparison to the overall DNS request-reply delay.