Source note · SIP registration failures
RFC 5626 exists because UAs behind NATs or firewalls often cannot accept inbound connections, so a server cannot reliably open a TCP connection or send unsolicited UDP to them.
Checked 2026-09-25
- Vendor
- not restricted
- Product
- SIP
- Subsystem
- nat-traversal
- Deployment
- any
- Region
- not restricted
- Release range
- RFC 5626
- Checked
- 2026-09-25
Sources
- RFC 5626: Managing Client-Initiated Connections in the Session Initiation Protocol (SIP) — IETF / RFC Editor · tier 1 standards and regulators · Section 3 Overview (3.1-3.2)
Cite this note
APA
WarmTransfer. (2026, September 25). SIP registration failures: source note sip-registration-failures-outbound-nat-problem. WarmTransfer. https://warmtransfer.net/knowledge/claims/sip-registration-failures-outbound-nat-problem
BibTeX
@misc{warmtransfer-claim-sip-registration-failures-outbound-nat-problem,
title = {SIP registration failures: source note sip-registration-failures-outbound-nat-problem},
author = {{WarmTransfer}},
year = {2026},
url = {https://warmtransfer.net/knowledge/claims/sip-registration-failures-outbound-nat-problem},
note = {Source note sip-registration-failures-outbound-nat-problem, checked 2026-09-25}
}