How much network overhead does TLS add compared to a non-encrypted connection?

Question

(Approximately) how many more bits of data must be transferred over the network during an encrypted connection compared to an unencrypted connection?

IIUC, once the TLS

Answer 1

I've gotten this question a few times, so I decided to write up a small explanation of the overhead with some sample numbers based on common case. You can read it on my blog at http://netsekure.org/2010/03/tls-overhead/.

Summary from blog post:

• The total overhead to establish a new TLS session comes to about 6.5k bytes on average.
• The total overhead to resume an existing TLS session comes to about 330 bytes on average.
• The total overhead of the encrypted data is about 40 bytes.