SIP 200 OK vs 606 Not Acceptable
SIP 200 (OK) is a 2xx Success response, while 606 (Not Acceptable) is a 6xx Global Failure response. 200 indicates that the request has succeeded. For INVITE, the call has been answered. For other methods, the action has been completed successfully. In contrast, 606 means that the user's agent was contacted successfully but some aspects of the session description (SDP) are not acceptable. Unlike 488, this is a global failure — no other server can satisfy this request.
Description
The request has succeeded. For INVITE, the call has been answered. For other methods, the action has been completed successfully.
When You See It
When a call is answered (INVITE 200 OK), a registration succeeds (REGISTER 200 OK), or a subscription is accepted (SUBSCRIBE 200 OK).
How to Fix
No fix needed — this is a success response. The caller should send an ACK to complete the three-way handshake for INVITE transactions.
Description
The user's agent was contacted successfully but some aspects of the session description (SDP) are not acceptable. Unlike 488, this is a global failure — no other server can satisfy this request.
When You See It
When the callee definitively cannot accept any of the offered media types or codecs. Different from 488 which is location-specific.
How to Fix
Check the Warning header or response body for which session parameters are unacceptable. Modify the SDP offer to use compatible codecs and media types.
Key Differences
200 is a 2xx Success response, while 606 is a 6xx Global Failure response.
SIP 200: The request has succeeded. For INVITE, the call has been answered. For other methods, the action has been completed successfully.
SIP 606: The user's agent was contacted successfully but some aspects of the session description (SDP) are not acceptable. Unlike 488, this is a global failure — no other server can satisfy this request.
You encounter 200 when when a call is answered (INVITE 200 OK), a registration succeeds (REGISTER 200 OK), or a subscription is accepted (SUBSCRIBE 200 OK).
You encounter 606 when when the callee definitively cannot accept any of the offered media types or codecs. Different from 488 which is location-specific.
When to Use Which
For 200 (OK): No fix needed — this is a success response. The caller should send an ACK to complete the three-way handshake for INVITE transactions. For 606 (Not Acceptable): Check the Warning header or response body for which session parameters are unacceptable. Modify the SDP offer to use compatible codecs and media types.