And now for something completely different

In computer networking, the term quality of service (QoS) describes resource management rather than the quality of a service. Quality of service implements control mechanisms to provide different priority to different users, applications, and data connections. It is used to guarantee a certain level of performance to data resources. The term quality of service is often used in the field of wide area network protocols (e.g. ATM) and telephony (e.g. VoIP), but rarely in conjunction with web applications. mod_qos is a quality of service module for the Apache web server implementing control mechanisms that can provide different levels of priority to different HTTP requests.

But why do you need quality of service for a web application? Well, web servers require threads and processes to serve HTTP requests. Each TCP connection to the web server occupies one of these threads respectively processes. Sometimes a server gets too busy to serve every request due to the lack of free processes or threads. Another parameter requiring control by mod_qos is the available bandwidth: all clients communicate to the server over a network link with limited bandwidth. Overfilling the link results in network congestion and poor performance.

Example situations where web applications require QoS:

• More resources are consumed if request processing by an application takes a long time, e.g. when request processing includes time consuming database queries.
• Oversubscription of link capabilities due to many concurrent clients uploading or downloading data.
• Penetration of the web server by attackers (DDoS).

mod_auth_oid is an Apache 2.2 module implementing an OpenID 2.0 Relying Party. It may be used to enable Apache base application to authenticate their users without needing access to user credentials such as a password. The module implements the necessary functions in order to verify the users OpenID identity using the appropriate OpenID Provider without using third party libraries. You only need an Apache server with some standard modules.

The mod_setenvifplus module allows you to set environment variables according to whether different aspects of the request match regular expressions you specify. These environment variables can be used by other parts of the server to make decisions about actions to be taken, e.g. by using mod_qos or to propagate supplemental information to the appliaction via HTTP header data. mod_setenvifplus is derived from the standard Apache module mod_setenvif.

mod_sslcrl is a module for the Apache Web server. It verifies the validity of client certificates againts Certificate Revocation Lists (CRL) of Certification Authorities (CA). It may be used in conjunction with mod_ssl when x509 client certificate authentication is used. mod_sslcrl replaces the mod_ssl directives SSLCARevocationFile and SSLCARevocationPath automatically downloading CRL files from CAs via HTTP(S).

HTTP Test Tool is a script based tool for testing and benchmarking web applications, web servers, proxy servers and web browsers.

httest can emulate clients and servers even in the same test script. Emulating servers is a unique feature, very usefull for testing proxy servers, web browsers and HTTP clients.