Source note · Passing call context with SIP UUI and custom headers

RFC 7434 requires a receiving SIP entity to ignore an isdn-uui User-to-User header whose 'encoding' parameter is present with a value other than 'hex'.

Checked 2026-10-02

A receiving SIP entity MUST ignore a received User-to-User header field if the 'encoding' header field parameter is present and the value is some other value than 'hex'

Vendor: not restricted
Product: not restricted
Subsystem: ISDN UUI interworking
Deployment: any
Region: not restricted
Release range: RFC 7434
Checked: 2026-10-02

Sources

RFC 7434: Interworking ISDN Call Control User Information with SIP — IETF / RFC Editor · tier 1 standards and regulators · Section 9

Cite this note

APA

WarmTransfer. (2026, October 2). Passing call context with SIP UUI and custom headers: source note sip-uui-context-passing-rfc7434-non-hex-ignored. WarmTransfer. https://warmtransfer.net/knowledge/claims/sip-uui-context-passing-rfc7434-non-hex-ignored

BibTeX

@misc{warmtransfer-claim-sip-uui-context-passing-rfc7434-non-hex-ignored,
  title  = {Passing call context with SIP UUI and custom headers: source note sip-uui-context-passing-rfc7434-non-hex-ignored},
  author = {{WarmTransfer}},
  year   = {2026},
  url    = {https://warmtransfer.net/knowledge/claims/sip-uui-context-passing-rfc7434-non-hex-ignored},
  note   = {Source note sip-uui-context-passing-rfc7434-non-hex-ignored, checked 2026-10-02}
}

Read in context