Switchvox - How to diagnose 400 Bad Request

Sometimes a provider will reject outbound calls and in a packet capture it will show a 400 Bad Request message:

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You can see what is causing the Bad Request error by highlighting the line and expanding the Session Initiaition Protocol and Message Header fields

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In the above example it shows that there is a SIP syntax error on line 014 of the INVITE. You can now highlight the previous INVITE message and check line 14 to see what is causing the call to fail:

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In this example the 400 Bad Request is caused by an Alert-Info header that adds a ringtone. Either the provider can be contacted to allow this header or the ring rule can be disabled to resolve.