Under RFC 7433 the User-to-User header field may appear in INVITE and BYE requests and in end-to-end responses to them (1xx other than 100, 2xx and 3xx).

Checked 2026-10-02

Vendor
not restricted
Product
not restricted
Subsystem
SIP User-to-User header
Deployment
any
Region
not restricted
Release range
RFC 7433
Checked
2026-10-02

Sources

Cite this note

APA

WarmTransfer. (2026, October 2). Passing call context with SIP UUI and custom headers: source note sip-uui-context-passing-rfc7433-methods-invite-bye. WarmTransfer. https://warmtransfer.net/knowledge/claims/sip-uui-context-passing-rfc7433-methods-invite-bye

BibTeX

@misc{warmtransfer-claim-sip-uui-context-passing-rfc7433-methods-invite-bye,
  title  = {Passing call context with SIP UUI and custom headers: source note sip-uui-context-passing-rfc7433-methods-invite-bye},
  author = {{WarmTransfer}},
  year   = {2026},
  url    = {https://warmtransfer.net/knowledge/claims/sip-uui-context-passing-rfc7433-methods-invite-bye},
  note   = {Source note sip-uui-context-passing-rfc7433-methods-invite-bye, checked 2026-10-02}
}

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