TLS / SSL Handshake Size

Context: The Wormly SSL Tester reports the size of an SSL handshake with your HTTPS server.

One aspect which can have a significant impact on the perceived performance of your web secure server is the amount of data transfer required to establish a SSL/TLS session.

The Wormly SSL Tester reports the size of the initial handshake; and a payload of around 4kB seems to be fairly typical.

Whilst 4kB may not seem like much in an era of broadband connections, it’s important to remember that the slow start algorithm is employed by the TCP protocol.

If the size of the certificate payload exceeds the initial congestion window, then the server will have to wait until the client acknowledges receipt of the packets already sent before resuming transmission.

The practical upshot of this is increased round-trips incurred before the session is established; which results in a slower connection experience for the end user.

By minimizing the size of your servers’ certificate chain, you can reduce the likelihood of overflowing the initial congestion window and improving connection performance.