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SIP response codes

SIP 406 Not Acceptable

The response format is not acceptable. The request has a problem on the sender’s side or cannot be completed at this server. Retrying the same request will not help.

406

Name: Not Acceptable
Class: 4xx · Client error
Defined in: RFC 3261
Q.850 cause towards the PSTN: 79 · Service or option not implemented, unspecified

The request has a problem on the sender’s side or cannot be completed at this server. Retrying the same request will not help.

What the response looks like

SIP/2.0 406 Not Acceptable
Via: SIP/2.0/UDP 203.0.113.10:5060;branch=z9hG4bK776asdhds
From: <sip:101@pbx.example>;tag=1928301774
To: <sip:+15551234567@pbx.example>;tag=a6c85cf
Call-ID: a84b4c76e66710@203.0.113.10
CSeq: 2 INVITE
Reason: Q.850;cause=79;text="Service or option not implemented, unspecified"
Content-Length: 0