Web Caching

Request Blocking

Request blocking refers to the act of denying certain requests based on some part of the request itself (usually the URL). Like it or not, a fair amount of the content available on the Web is generally considered to be offensive, the most obvious example being pornography. Some organizations that connect to the Internet feel it necessary to prevent their users from accessing these sites. A web cache is a logical place to implement per-request blocking.

The issues surrounding request blocking fall mostly into the political realm. Furthermore, these issues are not new or unique to the Web. Just as many companies say employees should not make phone-sex calls while at work, they also say workers should not view pornographic web sites. Similarly, a parent might say that children should not have easy access to sexually explicit material, whether in the form of a magazine, video, or web site. It is a policy decision, for employers and parents, whether and to what extent request blocking should be enabled. Classifying material into offensive or inoffensive categories is a political and ideological issue and far beyond the scope of this book. Even if the classification is not controversial, it is unlikely that a particular technique or implementation is perfect. Some legitimate sites may be incorrectly blocked. Similarly, sites that should be blocked may still be allowed through.

Several request-blocking products and services are available. Some of these are “plug-ins” ...