When we talked about the Diameter protocol in Diameter Overview, we mentioned that it relies on transport level protocols – TCP or SCTP.
SIP and Diameter stacks
I guess most of people are familiar with TCP. But not everyone is familiar with SCTP protocol yet. And that’s a pity because the Stream Control Transmission Protocol (SCTP) was designed especially for telcos as TCP is burdened with some limitations. Let’s explore SCTP’s basic featurers today. Btw. we should remind that SCTP is a must also in legacy networks, because SCTP is a part of Sigtran stack (SS7 over IP).
SIP and Diameter in Wireshark
And last but not least SCTP can also transport the SIP protocol (RFC 4168). It is not that common, but there are some operators benefiting from this option e.g. in case of NNI.
Real Time Communication 