Source note · SIP call forwarding and routing loops
RFC 7332 requires every type of SIP B2BUA to copy the Max-Forwards value it receives on its UAS side into the requests it generates on its UAC side, and to decrement that value.
Checked 2026-09-25
All B2BUA types MUST copy the received Max-Forwards header field from the received SIP request on their UAS side, to any request(s) they generate on their UAC side, and decrement the value.
- Vendor
- IETF
- Product
- SIP
- Subsystem
- B2BUA loop detection
- Deployment
- any
- Region
- not restricted
- Release range
- RFC 7332 (August 2014) onward
- Checked
- 2026-09-25
Sources
- RFC 7332: Loop Detection Mechanisms for Session Initiation Protocol (SIP) Back-to-Back User Agents (B2BUAs) — IETF / RFC Editor · tier 1 standards and regulators · Section 3 B2BUA Behavior, Max-Forwards requirement
Cite this note
APA
WarmTransfer. (2026, September 25). SIP call forwarding and routing loops: source note sip-forwarding-loops-b2bua-copy-decrement. WarmTransfer. https://warmtransfer.net/knowledge/claims/sip-forwarding-loops-b2bua-copy-decrement
BibTeX
@misc{warmtransfer-claim-sip-forwarding-loops-b2bua-copy-decrement,
title = {SIP call forwarding and routing loops: source note sip-forwarding-loops-b2bua-copy-decrement},
author = {{WarmTransfer}},
year = {2026},
url = {https://warmtransfer.net/knowledge/claims/sip-forwarding-loops-b2bua-copy-decrement},
note = {Source note sip-forwarding-loops-b2bua-copy-decrement, checked 2026-09-25}
}