asterisk users - Apr 2014 - Destruction of SIP dialog for OPTIONS requests

Hi all,
I'd like to verify whether an Asterisk behaviour is expected or not, and
ask for advice for the best solution.

I have Asterisk 1.8.17.0 on debian wheezy, listening on UDP and TCP 5060,
and TLS 5061.
Asterisk is part of a dispatcher set in Kamailio (4.1.3), and is marked as
AP (Active Probing): this means that Kamailio sends an OPTIONS request
every N seconds to verify Asterisk is available.

When I try to use TCP or TLS, after some time, Asterisk is marked as
Inactive.

For what I've seen, the reason is that after 32" after the first
OPTIONS,
Asterisk destroys the related dialog, and stops replying to the OPTIONS
requests on the existing TCP socket.
Kamailio times out, and re-opens a new TCP socket when the next probe is
due. This works again, and probing is successful, until Asterisk destroys
the dialog again.

I've configured Asterisk so that is replies with a 200 OK.

Is there a way I can avoid the dialog destruction, and let Kamailio use the
same TCP socket for whatever time is necessary, rather than about 30"?
Is my Asterisk behaving as expected?
What's your advice for this type of configuration?

Thanks in advance,

-- 
Giacomo Vacca
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