5.21. Web proxies and web caches

Web proxies are servers in the network which proxy the traffic towards the web server by terminating the TCP session towards the client and establishing a TCP session towards the web server. The data retrieved on the session towards the web server is forwarded to the client.

Figure 5.159. The TCP sessions towards a web proxy

.--------.          .----------.          .------------.
| client | <------> | web proxy | <------> | web server |
'--------'          '----------'          '------------'
       TCP session from         TCP session from
      client to web proxy       web proxy to server
       on TCP port 8080          on TCP port 80

Web proxies can also have a caching functionality, where static objects requested by a remote web server are stored on the web proxy and served to the client if the web proxy knows that the object is still valid. This will save traffic on the link between the web proxy and the web server, but the latency is often still there.

For the Steelhead appliance, the issue is that the web proxy is serving both plain-text and encrypted traffic on TCP port 8080 which makes an optimal optimization on that TCP port impossible.

The details of which web proxy server to use are configured on the client's web browser and there are two approaches:

By selecting different TCP port numbers for different kinds of traffic, for example TCP port 8080 for HTTP traffic and TCP port 8443 for HTTPS traffic, it will be possible for the Steelhead appliances to only optimize the plain-text HTTP traffic on TCP port 8080 and pass-through the encrypted HTTPS traffic on TCP port 8443.