Outbound SIP call remains ringing after answer — provider receives no ACK after 200 OK

Telephony
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1

Hi LiveKit team,

We’re debugging an outbound SIP call through Photon/Spectrum.

The recipient answered, but LiveKit remained at sip.callStatus=ringing.
CreateSIPParticipant(wait_until_answered=True) eventually returned HTTP 408, so our TTS never started.

Photon checked its server-side SIP trace and confirmed:

  • The carrier sent 200 OK at 2026-08-11 17:50:44.663 UTC
  • Photon forwarded it to LiveKit at 17:50:44.664 UTC
  • Photon did not receive an ACK
  • After approximately 32 seconds without an ACK, Photon terminated the call with BYE

Call details:

  • LiveKit SIP Call ID: SCL_WvjPdttCtPMQ
  • Room ID: RM_gCPi4nwNhHig
  • Photon-side Call-ID: epBue8Uzc1dMefx6Mn3ljf3BmRSG
  • Caller ID: +1 628-488-4084
  • Destination: ending in 2278
  • Trunk: TLS to sip.spectrum.photon.codes:5061
  • Codec: PCMU/8000 + telephone-event

We verified that the LiveKit outbound trunk address, TLS transport, digest credentials, and caller ID are configured correctly.

Could you please check:

  1. Did LiveKit receive the 200 OK?

  2. Did LiveKit generate an ACK, and to which IP, port, Request-URI, and transport was it sent?

  3. Did the Contact or Record-Route headers affect ACK routing?

  4. Could you inspect or share the PCAP for this call?

Thanks!

2

Hi, I see an error in the server logs indicating we are not receiving audio packets.

This is most typically a firewall or network issue, can you please review the firewall info at Configuring firewalls | LiveKit Documentation ?

The call did not generate a PCAP on our end but I see server logs that imply we received the 200 OK.

I don’t have a log that the ACK was generated, but it would have been. Though, without a pcap, I can’t say where it was sent. It looks like both ends gave up, since we also gave up as we had no media.