Source note · SIP 503 and trunk out-of-service failures
Under RFC 7339, an overloaded server that is throttling MUST reject some requests from non-participating clients with 503 without a Retry-After header.
Checked 2026-09-25
A SIP server that is in overload and has started to throttle incoming traffic MUST reject some requests from non-participating clients with a 503 (Service Unavailable) response without the Retry-After header.
- Vendor
- IETF
- Product
- SIP
- Subsystem
- overload control
- Deployment
- any
- Region
- not restricted
- Release range
- current as of 2026-09-25
- Checked
- 2026-09-25
Sources
- RFC 7339: Session Initiation Protocol (SIP) Overload Control — IETF / RFC Editor · tier 1 standards and regulators · Section 5.10.2
Cite this note
APA
WarmTransfer. (2026, September 25). SIP 503 and trunk out-of-service failures: source note sip-503-trunk-failures-rfc7339-503-no-ra. WarmTransfer. https://warmtransfer.net/knowledge/claims/sip-503-trunk-failures-rfc7339-503-no-ra
BibTeX
@misc{warmtransfer-claim-sip-503-trunk-failures-rfc7339-503-no-ra,
title = {SIP 503 and trunk out-of-service failures: source note sip-503-trunk-failures-rfc7339-503-no-ra},
author = {{WarmTransfer}},
year = {2026},
url = {https://warmtransfer.net/knowledge/claims/sip-503-trunk-failures-rfc7339-503-no-ra},
note = {Source note sip-503-trunk-failures-rfc7339-503-no-ra, checked 2026-09-25}
}