Source note · SIP registration failures
RFC 4320 forbids answering a non-INVITE request with 100 over an unreliable transport such as UDP before the client's Timer E would have reached T2.
Checked 2026-09-25
- Vendor
- not restricted
- Product
- SIP
- Subsystem
- transactions
- Deployment
- any
- Region
- not restricted
- Release range
- RFC 4320
- Checked
- 2026-09-25
Sources
- RFC 4320: Actions Addressing Identified Issues with the Session Initiation Protocol's (SIP) Non-INVITE Transaction — RFC Editor / IETF · tier 1 standards and regulators · Section 4.1 Action 1
Cite this note
APA
WarmTransfer. (2026, September 25). SIP registration failures: source note sip-registration-failures-no-early-100-udp. WarmTransfer. https://warmtransfer.net/knowledge/claims/sip-registration-failures-no-early-100-udp
BibTeX
@misc{warmtransfer-claim-sip-registration-failures-no-early-100-udp,
title = {SIP registration failures: source note sip-registration-failures-no-early-100-udp},
author = {{WarmTransfer}},
year = {2026},
url = {https://warmtransfer.net/knowledge/claims/sip-registration-failures-no-early-100-udp},
note = {Source note sip-registration-failures-no-early-100-udp, checked 2026-09-25}
}