Squid is the most popular Web caching software in use today, and it works on a variety of platforms including Linux, FreeBSD, and Windows. Squid improves network performance by reducing the amount of bandwidth used when surfing the Web. It makes web pages load faster and can even reduce the load on your web server. By caching and reusing popular web content, Squid allows you to get by with smaller network connections. It also protects the host on your internal network by acting as a firewall and proxying your internal web traffic. You can use Squid to collect statistics about the traffic on your network, prevent users from visiting inappropriate web sites at work or school, ensure that only authorized users can surf the Internet, and enhance your privacy by filtering sensitive information from web requests. Companies, schools, libraries, and organizations that use web-caching proxies can look forward to a multitude of benefits. Written by Duane Wessels, the creator of Squid, Squid: The Definitive Guide will help you configure and tune Squid for your particular situation. Newcomers to Squid will learn how to download, compile, and install code. Seasoned users of Squid will be interested in the later chapters, which tackle advanced topics such as high-performance storage options, rewriting requests, HTTP server acceleration, monitoring, debugging, and troubleshooting Squid. Topics covered include: Compiling and installing Squid, Running Squid, Using Squid's sophisticated access controls, Tuning disk storage for optimal performance, Configuring your operating system for HTTP interception, Forwarding Requests to other web caches, Using redirectors to rewrite user requests, Monitoring Squid with the cache manager and SNMP, Using Squid to accelerate and protect HTTP servers, Managing bandwidth consumption with Delay Pools.

Table of Contents

Preface; 1. Introduction; Web Caching; A Brief History of Squid Hardware and Operating System Requirements; Squid Is Open Source Squid's Home on the Web; Getting Help; Getting Started with Squid Exercises; 2. Getting Squid; Versions and Releases; Use the Source, Luke; Precompiled Binaries; Anonymous CVS; devel.squid-cache.org; Exercises; 3. Compiling and Installing; Before You Start; Unpacking the Source; Pretuning Your Kernel; The configure Script; make; make Install; Applying a Patch Running configure Later; Exercises; 4. Configuration Guide for the Eager; The squid.conf Syntax; User IDs; Port Numbers Log File Pathnames; Access Controls; Visible Hostname;; Administrative Contact Information; Next Steps; Exercises 5. Running Squid; Squid Command-Line Options; Check Your Configuration File for Errors; Initializing Cache Directories Testing Squid in a Terminal Window; Running Squid as a Daemon Process; Boot Scripts; A chroot Environment; Stopping Squid Reconfiguring a Running Squid Process; Rotating the Log Files Exercises; 6. All About Access Controls; Access Control Elements Access Control Rules; Common Scenarios; Testing Access Controls Exercises; 7. Disk Cache Basics; The cache_dir Directive Disk Space Watermarks; Object Size Limits; Allocating Objects to Cache Directories; Replacement Policies; Removing Cached Objects; refresh_pattern; Exercises; 8. Advanced Disk Cache Topics; Do I Have a Disk I/O Bottleneck?; Filesystem Tuning Options; Alternative Filesystems; The aufs Storage Scheme The diskd Storage Scheme; The coss Storage Scheme; The null Storage Scheme; Which Is Best for Me?; Exercises 9. Interception Caching; How It Works; Why (Not) Intercept? The Network Device; Operating System Tweaks; Configure Squid Debugging Problems; Exercises; 10. Talking to Other Squids Some Terminology; Why (Not) Use a Hierarchy?; Telling Squid About Your Neighbors; Restricting Requests to Neighbors;; The Network Measurement Database; Internet Cache Protocol Cache Digests; Hypertext Caching Protocol; Cache Array Routing Protocol; Putting It All Together; How Do I ...; Exercises; 11. Redirectors; The Redirector Interface; Some Sample Redirectors; The Redirector Pool; Configuring Squid Popular Redirectors; Exercises; 12. Authentication Helpers Configuring Squid; HTTP Basic Authentication; HTTP Digest Authentication; Microsoft NTLM Authentication; External ACLs Exercises; 13. Log Files; cache.log; access.log store.log; referer.log; useragent.log; swap.state; Rotating the Log Files; Privacy and Security; Exercises; 14. Monitoring Squid; cache.log Warnings; The Cache Manager Using SNMP; Exercises; 15. Server Accelerator Mode; Overview Configuring Squid; Gee, That Was Confusing!; Access Controls Content Negotiation; Gotchas; Exercises; 16. Debugging and Troubleshooting; Some Common Problems; Debugging via cache.log Core Dumps, Assertions, and Stack Traces; Replicating Problems Reporting a Bug; Exercises; A. Config File Reference B. The Memory Cache; C. Delay Pools

Author Biography

Duane Wessels became interested in web caching in 1994 as a topic for his master's thesis in telecommunications at the University of Colorado, Boulder. He worked with members of the Harvest research project to develop web caching software. After the departure of other members to industry jobs, he continued the software development under the name Squid. Another significant part of Duane's research with the National Laboratory for Applied Network Research has been the operation of 6 to 8 large caches throughout the U.S. These caches receive requests from hundreds of other caches, all connected in a "global cache mesh."