the server sees the IP of the intermediate host. Transparency at the application layer means the client application uses the protocol in a different way. An example of a transparent HTTP request for a server: GET / HTTP/1.1 Host: example.org Connection: Keep-Alive An example non-transparent HTTP request for a proxy (cache): GET http://foo.bar/ HTTP/1.1 Proxy-Connection: Keep-Alive Application layer transparency is symmetric when the same working mode is used on both the sides. The transparency is asymmetric when the firewall (usually a proxy) converts server type requests to proxy type or vice versa. Transparency at the IP layer does not automatically mean application layer transparency. See also Data independence Replication transparency References Telecommunications Data management