RFC 7332: Loop Detection Mechanisms for Session Initiation Protocol (SIP) Back-to-Back User Agents (B2BUAs)

Publisher

IETF / RFC Editor

URL

https://www.rfc-editor.org/rfc/rfc7332.html

Published

2014-08-01

Updated

unknown

Accessed

2026-09-25

HTTP status

200

License

IETF Trust; RFC text may be reproduced with attribution under BCP 78; short excerpts and locators only

Source notes citing this source

• RFC 7332 requires B2BUAs to check the received Max-Forwards value and to reject or respond to the request, rather than pass it on, when the value is zero. in context
• 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. in context
• Under RFC 7332, when a B2BUA generates a request on its UAC side and the received request had no Max-Forwards header field, the B2BUA must create one; the recommended value is 70. in context
• If an SBC or PBX acting as a B2BUA starts each outgoing leg at a fresh Max-Forwards value instead of copying and decrementing the received value, a call looping between that device and a carrier never runs Max-Forwards down to zero and is not stopped by a 483. inferred in context
• RFC 7332 recommends that B2BUAs implement the Via-based loop-detection mechanism that RFC 5393 defines for proxies, and requires them to copy any received Max-Breadth header field to the requests they generate. in context

Cite this source record

APA

WarmTransfer. (2014, August 1). RFC 7332: Loop Detection Mechanisms for Session Initiation Protocol (SIP) Back-to-Back User Agents (B2BUAs). WarmTransfer. https://warmtransfer.net/knowledge/sources/ietf-rfc-7332-b2bua-loop-detection

BibTeX

@misc{warmtransfer-ietf-rfc-7332-b2bua-loop-detection,
  title  = {RFC 7332: Loop Detection Mechanisms for Session Initiation Protocol (SIP) Back-to-Back User Agents (B2BUAs)},
  author = {{WarmTransfer}},
  year   = {2014},
  url    = {https://warmtransfer.net/knowledge/sources/ietf-rfc-7332-b2bua-loop-detection},
  note   = {IETF / RFC Editor, accessed 2026-09-25}
}