For an INVITE without SDP, RFC 6337 describes the UAS offer as going in the first reliable 1xx response (answered in PRACK) or, if none, in the final 2xx response, and says the UAS ought not include SDP in other responses to that INVITE.

Checked 2026-09-25

Vendor
IETF
Product
SIP
Subsystem
offer-answer
Deployment
any
Region
not restricted
Release range
RFC 6337 (Informational)
Checked
2026-09-25

Sources

Cite this note

APA

WarmTransfer. (2026, September 25). SIP early offer and delayed offer: source note sip-early-delayed-offer-rfc6337-offerless-invite-offer-location. WarmTransfer. https://warmtransfer.net/knowledge/claims/sip-early-delayed-offer-rfc6337-offerless-invite-offer-location

BibTeX

@misc{warmtransfer-claim-sip-early-delayed-offer-rfc6337-offerless-invite-offer-location,
  title  = {SIP early offer and delayed offer: source note sip-early-delayed-offer-rfc6337-offerless-invite-offer-location},
  author = {{WarmTransfer}},
  year   = {2026},
  url    = {https://warmtransfer.net/knowledge/claims/sip-early-delayed-offer-rfc6337-offerless-invite-offer-location},
  note   = {Source note sip-early-delayed-offer-rfc6337-offerless-invite-offer-location, checked 2026-09-25}
}

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