On 28 Dec 2015, at 09:51, Mititelu Stefan <fanx07@gmail.com> wrote:

Hello,
What is the simplest way to configure Kamailio to generate periodical OPTIONS to the caller, for an established dialog?
Can you give me some starting references?

To be SIP correct, a proxy may not insert any transactions in a dialog between two endpoints. The endpoints have the cseq counter and inserting anything will mess with the CSEQ.

Having said that, the dialog module has a keep-alive function that does this. It may generate strange error messages which is fine. You want to test the behaviour on a per-device basis.