In my setup I am using client certs, and the client devices are iPhones running iOS 9.0.
In comparing some network traces I noticed that in some cases, the server asks for the client certificate for the first time, and then for all future connections (at least within the next minute) it will not ask for it again. After the first connection I will just see "Server Hello, Change Cipher Spec, Finished", where for the initial case I will the proper back and forth which involves transferring the server and well as the "RSA Encrypted PreMaster Secret".
However with some other clients (which have a different version of the software which handles the SSL) I see that the server will frequently ask the client again and again for the client Cert.
Which is these behaviors is correct and what elements determine whether the Server decides to ask same client (based IP address) again for the client cert?