IBM HTTP Server product features IBM HTTP Server documentation

Looking at the product

This section takes a high level look at the IBM HTTP Server, including new functions for this release, locating the IBM HTTP Server documentation and other valuable sources of information. Licensing and acknowledgments are also noted here. Links to related topics appear at the end of this section.

Identifying IBM HTTP Server offerings

The IBM HTTP Server, powered by Apache, is a Web server based on the Apache Web server developed by the Apache Software Foundation (ASF) ( The IBM HTTP Server includes several functions not available in the Apache Web server:

  • InstallShield for multiple platforms, enabling consistent installation of the IBM HTTP Server to alternate directories.
  • Secure Sockets Layer (SSL) secure connections support.
  • Fast Response Cache Accelerator (FRCA) support (Windows and AIX 5.x operating systems). IBM has extended Apache to work with the IBM Fast Response Cache Accelerator, or Cache Accelerator. The Cache Accelerator acts as an in-kernel mini HTTP GET engine and HTTP content cache. The FRCA serves static Web pages significantly faster than the Apache Web server, without the Cache Accelerator, enabled by default. Disable the Cache Accelerator completely through configuration file directives.
  • Dynamic content generation with FastCGI.
  • Simultaneous installation of the IBM HTTP Server in multiple languages on all platforms.
  • Web server LDAP authentication protection through an LDAP module.

Looking at changes to Apache 2.0 and the Apache Portable Runtime

IBM HTTP Server V2.0 is based on a recent General Availability (GA) release of Apache 2.0 and the Apache Portable Runtime (APR), distributed by the Apache Software Foundation. IBM makes some limited changes to Apache 2.0 and APR when creating IBM HTTP Server V2.0. These changes can be broadly classified into two categories:
  1. Bug fixes:
    IBM HTTP Server is based on GA releases of Apache 2.0 and the APR. The IBM development team selectively backports fixes from the current Apache 2.0 and APR development source code repositories (hosted at into IBM HTTP Server. Security fixes receive the highest priority.
  2. Changes to support IBM modules:
    IBM maintains some changes to support specific IBM requirements.

IBM HTTP Server V2.0 source code is 100% compatible with the release of Apache 2.0 and the APR upon which it is based. By maintaining the proper compiler settings, modules compiled to be dynamically loaded into Apache 2.0 will work with IBM HTTP Server V2.0, subject to the normal restrictions the Apache Module Magic Number imposes.

Changes to Apache 2.0:
IBM does not make any significant changes to the Apache 2.0 code.

Changes to Apache Portable Runtime:
IBM has added a socket IO redirection layer application programming interface (API) to the APR. This new API does not change the existing API of APR, as distributed by the Apache Software Foundation. This change enables IBM to introduce some serviceability enhancements and solve some problems with cleanly integrating SSL and the FRCA kernel cache accelerator, without requiring additional changes to the Apache 2.0 code.

The ihs_patch file, which installs in the readme directory, contains all source code changes made to Apache 2.0 and APR. The CHANGES_HTTPD, CHANGES_APR, and CHANGES_APRUTIL files, which install in the readme directory, contain a text description of the changes.

Source code for IBM-specific modules is not provided.

Pertains to Windows users

Note: The IBM HTTP Server, powered by Apache for the Windows operating system, does not run on Windows 95 or Windows 98 operating systems. If you need an Apache Web server for either the Windows 95 or Windows 98 operating system, you can get the source and binary installation images, from the Apache Web site:

Identifying new functions in this release

New functions for this release include:

  • Fast Response Cache Accelerator on AIX 5.x
  • FastCGI

    FastCGI, a language independent, scalable, open extension to Common Gateway Interface (CGI), provides high performance and persistence without the limitations of server-specific APIs.

Upgrading from Apache 1.3 to Apache 2.0

For a comprehensive list of tips for upgrading Apache 1.3 to Apache 2.0, visit

Finding IBM HTTP Server documentation

The documentation available for this release, in HTML format resides in the <IHS install root>/manual/ibm/<Lang> directory. For the most recent documentation, visit the IBM HTTP Server Web site.

Locating other sources of information

Several good Internet news groups cover HTTP servers in general. These groups have information about all the popular Web servers and could help you find answers to your questions, so check the news group archives first:

  • USENET, ibm.websphere.http-servers
  • comp.infosystems.www.servers
  • USENET newsgroup
  • USENET newsgroup comp.infosystems.www.servers.unix


See the file called LICENSE.IBM

Acknowledging copyrighted work

We wish to acknowledge the following copyrighted works that make up portions of the IBM HTTP Server, based on Apache software:

Portions of this software were developed at the National Center for Supercomputing Applications at the University of Illinois at Urbana-Champaign.

This software contains code derived from the RSA Data Security Inc. MD5 Message-Digest Algorithm, including various modifications by Spyglass Inc., Carnegie Mellon University, and Bell Communications Research, Inc. (Bellcore).

This package contains software written and copyrighted by Henry Spencer. See the file called src/regex/COPYRIGHT.

The NT port was started with code provided to the IBM HTTP Server based on Apache Group by Ambarish Malpani, of ValiCert, Inc. (

Finding related information

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