Greetings list, 
I am forking a call to multiple destinations and want to keep the only branch which sends quicker first 180/183 reply and cancel the remaining branches. Below is my related cfg snippet.


modparam("tm", "failure_reply_mode", 3)
modparam("tm", "fr_timer", 30000)
modparam("tm", "fr_inv_timer", 120000)
modparam("tm", "cancel_b_method", 2)
...
route[SIPOUT] {
        if (uri==myself) return;

        append_hf("P-hint: outbound\r\n");
        append_branch();
        append_branch();
        route(RELAY);
        exit;
}
onreply_route[MANAGE_REPLY] {
        xdbg("incoming reply\n");
        if(status=~"[12][0-9][0-9]") {
                xlog("L_INFO","Received $rs (IP:$si:$sp)\n");
                if(status=~"18[03]"){
                        t_cancel_branches("others");
                        xlog("L_INFO","cancelled all other branches\n");
                }
                route(NATMANAGE);
        }
}
...

But I see kamailio does not instantly send CANCEL to other branches after it has received 180/180 from any branch. 
Kamailio is sending CANCEL to other branches after they start sending 180/183 one by one. How can I cancel all other branches instantly?

I am sure there is something wrongly configured in my configuration.  

Any suggestion is much appreciated. 
Best Regards.