Web Caching

What You Will and Won’t Find Here

Chapter 1 introduces caching and provides some background material to help the rest of the book make sense. In addition, companies that provide caching products are listed here. In Chapter 2, we’ll dive into the Hypertext Transfer Protocol and explore its features for caching. Chapter 3 is relatively nontechnical and discusses some of the controversies that surround web caching, such as copyrights and privacy.

In Chapter 4, you’ll see the various ways to configure user agents (browsers) for caching, with a focus on Netscape Navigator and Microsoft Internet Explorer. Many administrators prefer to automatically intercept and divert HTTP connections to a cache. We’ll talk about that in Chapter 5. Then, in Chapter 6, we’ll turn to servers and see how content providers can make their information cache-friendly.

Chapter 7 and Chapter 8 are about cache hierarchies. First we’ll talk about them in general, including why you should or should not participate in a hierarchy. Then you’ll learn about the protocols caches use to communicate with each other. Chapter 9 is a short chapter about cache clusters. Although clusters have some things in common with cache hierarchies, it is easier to understand some of the nuances after you’ve learned about the intercache protocols.

In Chapter 10, I’ll walk you through some of the decisions you’ll face in procuring and building a caching service for your organization. Following that, Chapter 11 offers advice on monitoring the health of your caches once they are operational. For the Unix-savvy, I’ll show how to set up UCD-SNMPD and RRDTool for this purpose. Chapter 12 is about benchmarking the performance of caches.

I analyze some logfiles from production caches in Appendix A. Here you can see some sample file size distributions, content types, HTTP headers, and hit ratio simulations. The next four appendixes are about intercache protocols. Appendix B describes the technical details of ICP. Appendix D does the same for HTCP, Appendix C for CARP, and Appendix E for cache digests. Appendix F is a list of HTTP status codes from RFC 2616. Appendix G contains the text of a U.S. copyright statute that mentions caching. Finally, in Glossary, you’ll find definitions for many of the acronyms I use in this book.

The new, hot topics in the caching industry are streaming media and content distribution networks. This book focuses on HTTP and FTP caching techniques with proven results, eschewing technology that is still evolving.