Source note · SIP response codes and failure interpretation
A 400 Bad Request response means the server could not parse the request because of malformed syntax; the reason phrase should identify the specific syntax problem, such as a missing header field.
Checked 2026-09-04
- Vendor
- not restricted
- Product
- not restricted
- Subsystem
- sip
- Deployment
- not restricted
- Region
- not restricted
- Release range
- not restricted
- Checked
- 2026-09-04
Sources
- SIP: Session Initiation Protocol (RFC 3261) — IETF · tier 1 standards and regulators · section-21.4.1
Cite this note
APA
WarmTransfer. (2026, September 4). SIP response codes and failure interpretation: source note sip-400-bad-request. WarmTransfer. https://warmtransfer.net/knowledge/claims/sip-400-bad-request
BibTeX
@misc{warmtransfer-claim-sip-400-bad-request,
title = {SIP response codes and failure interpretation: source note sip-400-bad-request},
author = {{WarmTransfer}},
year = {2026},
url = {https://warmtransfer.net/knowledge/claims/sip-400-bad-request},
note = {Source note sip-400-bad-request, checked 2026-09-04}
}