https://siptrain.com/blog/ Deep technical writing on SIP, RTP, SBCs, SS7/SIGTRAN, and carrier voice engineering. en https://siptrain.com/blog/sip-invite-lifecycle https://siptrain.com/blog/sip-invite-lifecycle Mon, 27 Apr 2026 09:00:00 +0000 The INVITE state machine, the retransmission timers you actually need to memorise, and the 2xx-vs-non-2xx ACK routing distinction. https://siptrain.com/blog/rtcp-in-practice https://siptrain.com/blog/rtcp-in-practice Mon, 20 Apr 2026 09:00:00 +0000 Reading SR/RR fluently — jitter in RTP units, RTT from LSR/DLSR, and what to do when your trace shows two RTCP packets in a 30-second call.