Application proxies

An application proxy or application proxy server receives requests intended for another server and acts on the client's behalf (as the client's proxy) to obtain the requested service. You often use an application proxy server when the client and the server are incompatible for direct connection. For example, the client is unable to meet the security authentication requirements of the server but should be permitted some services. Characteristics of an application proxy include the following:

• Breaks the TCP/IP connection between a client and server; IP forwarding is not required.
• Hides the internal client IP addresses; only the public IP address of the proxy server is visible from the external network
• Provides detailed access logs
• Authenticates uses
• Caches information

The most common type of proxy is the HTTP proxy. Most HTTP proxies also handle Secure HTTP (HTTPS) and file transfer protocol (FTP). The SMTP mail relay is an example of an application proxy.

The main drawback of application proxies is that they must support the application for which they are performing the proxy function. Many TCP/IP applications are not supported by proxy servers. In addition, application proxies do not typically encrypt data.

Some Universal Connection applications can flow through a standard HTTP proxy. The HTTP proxy must support SSL tunneling and can optionally require HTTP Basic Authentication.

i5/OS™ V5R4 includes a service and support HTTP Proxy which can be used specifically for Universal Connection applications if you want one partition or system providing connectivity for others.