While reading this book, you may want to consult some of these other resources for more information (I'll refer to them throughout this book):
The Design and Implementation of the 4.4 BSD Operating System by Marshall Kirk McKusick, Kieth Bostic, Michael J. Karels, and John S. Quarterman (Addison-Wesley Longman)
DNS and BIND by Paul Albitz and Cricket Liu (O'Reilly & Associates)
HTTP: The Definitive Guide by David Gourley and Brian Totty (O'Reilly)
Load Balancing Servers, Firewalls, and Caches by Chandra Koopurapu (John Wiley & Sons)
Mastering Regular Expressions by Jeffrey E. F. Friedl (O'Reilly)
Server Load Balancing by Tony Bourke (O'Reilly)
Unix System Administration Handbook and Linux System Administration Handbook by Evi Nemeth, Garth Snyder, Scott Seebass, and Trent R. Hein (Prentice Hall)
My book, Web Caching (O'Reilly)
RFC 1413: Identification Protocol
RFC 1738: Uniform Resource Locators (URL)
RFC 2186: Internet Cache Protocol (ICP), Version 2
RFC 2187: Application of Internet Cache Protocol (ICP), Version 2
RFC 2396: Uniform Resource Identifiers (URI): Generic Syntax
RFC 2616: Hypertext Transfer ProtocolHTTP/1.1
RFC 2617: HTTP Authentication: Basic and Digest Access Authentication
RFC 2756: Hypertext Caching Protocol
RFC 2817: Upgrading to TLS Within HTTP/1.1
RFC 3040: Internet Web Replication and Caching Taxonomy
RFC 3143: Known HTTP Proxy/Caching Problems
Caching-related web sites, such as http://www.caching.com/ and http://www.web-cache.com/