RFC 6337 says an answer to an offer with c=IN IP4 0.0.0.0 must still choose its direction attribute from the direction attribute of the offered stream.

Checked 2026-09-24

If a UA generates an answer to the offer received with "c=IN IP4 0.0.0.0", the direction attribute of the accepted media stream in the answer must still be based on direction attribute of the offered stream.
Vendor
IETF
Product
SIP
Subsystem
legacy hold
Deployment
any
Region
not restricted
Release range
RFC 6337 as published
Checked
2026-09-24

Sources

Cite this note

APA

WarmTransfer. (2026, September 24). Hold resume and conference signaling: source note hold-resume-conference-6337-zero-addr-answer-direction. WarmTransfer. https://warmtransfer.net/knowledge/claims/hold-resume-conference-6337-zero-addr-answer-direction

BibTeX

@misc{warmtransfer-claim-hold-resume-conference-6337-zero-addr-answer-direction,
  title  = {Hold resume and conference signaling: source note hold-resume-conference-6337-zero-addr-answer-direction},
  author = {{WarmTransfer}},
  year   = {2026},
  url    = {https://warmtransfer.net/knowledge/claims/hold-resume-conference-6337-zero-addr-answer-direction},
  note   = {Source note hold-resume-conference-6337-zero-addr-answer-direction, checked 2026-09-24}
}

Read in context