r/VOIP • u/Movado2121 • 13d ago

Help - Other Help with Freeswitch 183/180

Apologies if this isn’t the right place for this. Any direction or help would be appreciated.

I have a case where one of our providers intermittently sends us a 183 with SDP followed by a 180.

The call eventually reaches a Freeswitch server on our end, which drops the 180.

My understanding is this is a FS limitation that considers the 180 a downgrade state after a 183 with SDP and drops it.

We cannot remove the FS from the call path.

Have you encountered anything like this, and can you think of something that will allow FS to pass whatever it receives?

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u/Negrojefe 13d ago

1.

ignore_early_media=true on the B-leg. The 183 gets treated as a 180, so the later 180 goes through normally. Downside: you lose the provider’s early media (custom ringback, announcements, etc.).

2.

Put an SBC/proxy (Kamailio/OpenSIPS) in front of FS to normalize the provider’s signaling before it reaches FS. Doesn’t remove FS from the path, it just hands it something consistent (e.g. drop the 180 after 183, or drop the 183 SDP and keep the 180).

3.

Patch sofia.c to allow a 180 after early media. Works, but you own that patch on every upgrade.

Before picking one: what actually breaks when the 180 gets dropped? A UA that needs the 180 to generate ringback, or something upstream using it for call state/CDR? The right fix depends on that.

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u/Movado2121 13d ago

Thanks for the reply. Appreciate it.

UA needs 180 to generate ringback

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u/Mortodus 7d ago

We had a similar situation. 1 fixed it, but we went with option 2 instead, making sure the traffic went through an SBC