18 | 16 | * [http://httpd.apache.org/docs/2.2/ssl/ssl_faq.html#vhosts2 Why is it not possible to use Name-Based Virtual Hosting to identify different SSL virtual hosts?] |
19 | 17 | * It is possible, but only if using a 2.2.12 or later web server, built with 0.9.8j or later OpenSSL. This is because it requires a feature that only the most recent revisions of the SSL specification added, called Server Name Indication (SNI). |
20 | 18 | * The reason is that the SSL protocol is a separate layer which encapsulates the HTTP protocol. So the SSL session is a separate transaction, that takes place before the HTTP session has begun. The server receives an SSL request on IP address X and port Y (usually 443). Since the SSL request did not contain any Host: field, the server had no way to decide which SSL virtual host to use. Usually, it just used the first one it found which matched the port and IP address specified. |