Configure remote HTTP

HTTP (Hypertext Transfer Protocol) is a lightweight communications protocol for interprocess communication. Communications between a Web server and the WebSphere Application Server installed on a single machine, as well as communications across the network, use the HTTP protocol.

Remote HTTP refers to the use of HTTP protocol as a transport mechanism to communicate between two machines or logical partitions in the WebSphere Application Server environment. The WebSphere Application Server Web server plugin component uses remote HTTP to forward requests from the Web server to one or more application servers.

The WebSphere Application Server plugin resides on the Web server machine and is specific to the Web server. The remote Web server machine can be either of these:

• An iSeries machine running IBM HTTP Server (powered by Apache) or the Lotus Domino Web server.
• A non-iSeries machine running any of the other supported Web servers on a platform supported by WebSphere Application Server. For a list of supported non-iSeries platforms, see Workstation prerequisites for installing WebSphere Application Server.

Remote HTTP is one option that supports a demilitarized zone (DMZ) configuration. Use remote HTTP to forward client requests to one or more protected application servers that run behind a firewall.

Advantages of remote HTTP

• It does not require a Java process to run on the Web server machine.
• It supports demilitarized zone topologies
• It supports firewalls that use Network Address Translation (NAT).
• It minimizes the number of open ports in the firewall configuration. To communicate through the second firewall of the DMZ, remote HTTP requires one open port per application server. Remote HTTP does not require database access through the firewall between the Web server and the application server.
• You can configure the HTTP transport to use Secure Sockets Layer (SSL) to encrypt communication between the Web server and application server. For information on configuring SSL, see Configure SSL.

The WebSphere Application Server HTTP server plugin uses the plugin-cfg.xml file to determine which URLs route to an application server. To use remote HTTP, manually copy the plugin-cfg.xml configuration file from the application server machine to all of the Web server machines that communicate with the application server. Subsequent configuration changes may change the contents of the plugin-cfg.xml file. You must manually copy this file to the Web server machines whenever it is changed. The list below describes the tasks that change the plugin configuration files. After you perform any of these tasks, reconfigure the Web server machine by updating the plugin file:

• Add, remove, or change a virtual host.
• Change the HTTP port number of an application server.
• Add or remove an application server.
• Install or uninstall an enterprise application.
• Add or remove a cluster or cluster member.

These topics provide more information about configuring remote HTTP:

Configure the application server machine
This topic describes how to configure the machine that hosts your application server.

Configure the Web server machine
This topic describs how to configure the machine that hosts your Web server.

Sample plugin-cfg.xml file
The plugin-cfg.xml file contains configuration information for the Web server plugin. This topic provides a sample of a plugin-cfg.xml file.