SIP Message Analyzer
Paste a raw SIP request or response — even straight from a messy log — and get a plain-English explanation, grouped header table, Via stack, RFC 3261 lint (including NAT detection) and an SDP breakdown.
Parsed in your browser — nothing is uploaded
Explanation
Lint
Headers
Parse, lint, explain — then diagnose
The analyzer is deterministic and instant: the explanation is template-driven from parsed facts, not an LLM. For responses it consults a failure-diagnosis knowledge base keyed on the status code — 401/407 auth flows, 403 refusals, 408 fragmented-UDP timeouts, 488 codec mismatches and 491 glare — each with real-world causes.
FAQ
Does it work with real log formats?
Yes. It tolerates CRLF or LF, leading timestamps and log-level prefixes, sngrep/ngrep framing and compact header forms (v, f, t, i, m, c, l, k, s), which are normalised to long names.
What does the lint check?
Missing Max-Forwards, Via branch magic-cookie, CSeq method match, To-tag on responses, Contact presence, Content-Length vs body, and the high-value NAT lint — a private/CGNAT IP in Contact or the SDP c= line.
Can it parse just SDP?
The SDP panel appears whenever a message body contains m= lines, joining payload types with rtpmap/fmtp, showing direction (hold detection), ICE candidate types and DTLS fingerprint/setup role.
Related
SIP NAT debugging guide (PDF)
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Stuck on a real integration?
These tools come from day-job work: SMSC/STP/Sigtran, SMPP hookups, USSD gateways and WebRTC. If a paste here turned into a rabbit hole, that's exactly what we do.