There are some parameters like, rport, comedia in Nat settings. I know these parameters are for NAT traversal. I have already learnt comedia but i dont know rport. Why we use rport?
The rport option forces the use of rport functionality. The rport functionality is described in RFC3581 and essentially means send responses back to the source IP address and port of my request. If the device is behind NAT then this generally allows things to just work.
comedia for rtp? and rport for signalling?
Yes. Although there’s a third which is Contact rewriting, which sends new requests to the source IP address and port as well.