So far I assumed that the SPDY protocol, a more efficient version of HTTP, is still in some sort of experimental state but not widely used. Therefore I was very surprised when I recently saw it being used in a Google search request. For those of you wondering how I found out, take a look at the screenshot at the left. During TLS authentication, the servers sends the optional 'Next Protocol Negotiation' information element in the TLS 'Server Hello' message. As Firefox also supports SPDY, the communication then continues using this protocol. I couldn't observe this directly as everything is done inside the TLS encrypted traffic flow. However, there's only a single TCP connection to the server which is a pretty good indication that SPDY is used. Also, the Wikipedia entry on SPDY notes that there are quite a number of popular services in addition to Google that have also activated support for the protocol. How interesting!