Early Offer versus Delayed Offer SIP Invites

Publisher

46 Labs

URL

https://support.46labs.com/support/solutions/articles/156000368953-early-offer-versus-delayed-offer-sip-invites

Published

2025-07-03

Updated

unknown

Accessed

2026-09-25

HTTP status

200

License

46 Labs copyright; no-redistribution; short excerpts and locators only

Source notes citing this source

• For 46 Labs' carriers to send a reliable 18x on a delayed-offer call, the INVITE must include 100rel in the Supported or Require header. in context
• 46 Labs accepts delayed-offer INVITEs, with the SDP offer provided in the first reliable 18x response and/or the 200 OK. in context
• 46 Labs states that its PSTN carriers by default always send early-offer INVITEs. in context
• 46 Labs states that without a reliable 18x response carrying SDP, a delayed-offer INVITE cannot establish an early media session (for example network ringback). in context
• 46 Labs recommends that customers use early-offer INVITEs. in context

Cite this source record

APA

WarmTransfer. (2025, July 3). Early Offer versus Delayed Offer SIP Invites. WarmTransfer. https://warmtransfer.net/knowledge/sources/46labs-early-vs-delayed-offer

BibTeX

@misc{warmtransfer-46labs-early-vs-delayed-offer,
  title  = {Early Offer versus Delayed Offer SIP Invites},
  author = {{WarmTransfer}},
  year   = {2025},
  url    = {https://warmtransfer.net/knowledge/sources/46labs-early-vs-delayed-offer},
  note   = {46 Labs, accessed 2026-09-25}
}