Hello,

I used the below settings to test the keep-alive function within a dialog:

modparam("dialog", "default_timeout", 60)
modparam("dialog", "ka_timer", 10)
modparam("dialog", "ka_interval", 30)

and use dlg_set_property("ka-src") or dlg_set_property("ka-dst") to send OPTIONS to caller or callee.

A few questions to ask:

(1) What's the difference between ka_timer and ka_interval?

I read the http://www.kamailio.org/docs/modules/4.2.x/modules/dialog.html ,

but still can not understand very clearly.

I know the ka_interval means OPTIONS will be sent after 30 seconds when dialog started or last keep-alive has been done.

but I don't know how ka_timer works.

(2) From the packets captured I can see server sent OPTIONS and the client (caller or callee) sent back 200 OK.

     According to the document,
   "The dialog timeout is reset each time a sequential request is processed"
     However, the dialog was still timeout, it seems that the timeout value was not reset.

And I make the clients send the OPTIONS and frequently , the dialog never expires now.

So the refresh only works on the keep-alive sent by clients not the server here?

Thanks :)