Application proxies

An application proxy or application proxy server receives requests intended for another server and acts as the proxy of the client 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 cannot meet the security authentication requirements of the server but need to be permitted some services.

If you access the Internet through an application proxy, some Universal Connection applications might use the proxy. However, you must ensure that you select a configuration method that allows the remainder of your service information to connect through Universal Connection from your system to IBM without going through the application proxy.

The following list shows the characteristics of an application proxy:
  • Breaks the TCP/IP connection between a client and server, while IP forwarding is not required
  • Hides the internal client IP addresses and 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 Hypertext Transfer Protocol (HTTP) proxy. Most HTTP proxies also handle Hypertext Transfer Protocol Secure (HTTPS) and file transfer protocol (FTP). The Simple Mail Transfer Protocol (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 service information.

Some Universal Connection applications can flow through a standard HTTP proxy. The HTTP proxy must support Secure Sockets Layer (SSL) tunneling and can optionally require HTTP basic authentication.

The IBM® i operating system includes a service and support HTTP proxy that can be used specifically for Universal Connection applications if you want one partition or system to provide connectivity for others.