Source note · SIP 503 and trunk out-of-service failures
For server location, RFC 3263 defines failure as a 503 response, a transport failure (such as fatal ICMP errors on UDP or TCP connection failures), or the transaction timing out with no response.
Checked 2026-09-25
Failure also occurs if the transaction layer times out without ever having received any response.
- Vendor
- IETF
- Product
- SIP
- Subsystem
- DNS server location
- Deployment
- any
- Region
- not restricted
- Release range
- current as of 2026-09-25
- Checked
- 2026-09-25
Sources
- RFC 3263: Session Initiation Protocol (SIP): Locating SIP Servers — RFC Editor / IETF · tier 1 standards and regulators · Section 4.3
Cite this note
APA
WarmTransfer. (2026, September 25). SIP 503 and trunk out-of-service failures: source note sip-503-trunk-failures-rfc3263-failure-def. WarmTransfer. https://warmtransfer.net/knowledge/claims/sip-503-trunk-failures-rfc3263-failure-def
BibTeX
@misc{warmtransfer-claim-sip-503-trunk-failures-rfc3263-failure-def,
title = {SIP 503 and trunk out-of-service failures: source note sip-503-trunk-failures-rfc3263-failure-def},
author = {{WarmTransfer}},
year = {2026},
url = {https://warmtransfer.net/knowledge/claims/sip-503-trunk-failures-rfc3263-failure-def},
note = {Source note sip-503-trunk-failures-rfc3263-failure-def, checked 2026-09-25}
}