Happy New Year!
After spending a vacation for Christmas, I had my first AudioCodes virtual SBC implementation for this year and the error above took me a while to resolve. A while means few hours, thank God not days 🙂
So here’s the scenario.
ShoreTel -> SBC -> Optus
Essentially, the error above only happens to few outbound numbers. Almost all other numbers are working fine. Diagram below shows where the 488 Not Acceptable Here error comes from.
Based on the error, when Optus is sending a valid 180 Ringing to SBC, for some reason the SBC automatically sending “488 Not Acceptable Here” error to ShoreTel thus call is not able to connect successfully.
Solution: On the SBC’s IP Profile for ShoreTel leg, you have to disable “Early Media”. Search for parameter IpProfile_EnableEarlyMedia.
Note: When EarlyMedia is enabled, the device sends a SIP 18x response with SDP, allowing the media stream to be established before the call is answered. However, on above case the SBC doesn’t have Media channels and DSP resources on Feature Key license that’s why it can’t construct the SIP 18x response with SDP. So the only option is to disable it.