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 SSTPVERSION: 1.0
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
Figure 8: SSTP call setup for a proxy scenario