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

[BALL SUN]

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