[SR-Users] Kamailio IMS using returned SRV records for transport slelection

Hi All I am new to Kamailio IMS, and I just setup a testing environment where having P-CSCF, I-CSCF and S-CSCF. I would like to use make below works 1. SIP client <-> P-CSCF (either UDP or TCP, based on the transport tag) 2. P-CSCF <-> I-CSCF (TCP by default) 3. I-CSCF <-> S-CSCF (TCP by default) For point 2, I observed that P-CSCF actually will send DNS SRV query to DNS server for resolving _sip._udp. and _sip._tcp. I believed we can just disable the "_sip._udp." so that P-CSCF will always use TCP to communication wih I-CSCF. However, for point 3, I didnt notice I-CSCF send DNS SRV query, My question is how we can force I-CSCF to do that or is there any configuration that we should enable such that I-CSCF always use TCP to S-CSCF? - RBK