4.5 Handling HTTP Proxies

In the case that an SSTP tunnel is established through a proxy, the typical CONNECT request is as follows.

 Method: CONNECT
 Protocol Version: HTTP/1.1
 URI:  <Server Name>:443
 Host: <Server Name>:443

The SSTPVERSION field can be used by network administrators through forward proxies to filter the SSTP-based connection to go out of the network.

The response from the proxy follows. After the response is received, the SSL/TLS traffic is sent in an encrypted manner to the proxy, and the proxy relays the encrypted traffic between the client and the server.

 Protocol Version: HTTP/1.1
 Status Code: 200 HTTP_STATUS_OK
 Reason: Connection Established
 Proxy-Connection: Keep-Alive
 Connection: Keep-Alive

SSTP call setup for a proxy scenario

Figure 8: SSTP call setup for a proxy scenario