SIP 301 Moved Permanently vs 488 Not Acceptable Here
SIP 301 (Moved Permanently) is a 3xx Redirection response, while 488 (Not Acceptable Here) is a 4xx Client Failure response. 301 indicates that the user can no longer be found at the address in the Request-URI. The client should direct future requests to the new address in the Contact header. In contrast, 488 means that the request was understood but the session description (SDP) is not acceptable. The response may contain a list of acceptable media parameters.
Description
The user can no longer be found at the address in the Request-URI. The client should direct future requests to the new address in the Contact header.
When You See It
When a user has permanently changed their SIP address. All future calls should be directed to the new URI.
How to Fix
Update your address book or routing tables to use the new Contact URI provided in the response.
Description
The request was understood but the session description (SDP) is not acceptable. The response may contain a list of acceptable media parameters.
When You See It
When codec negotiation fails — the callee cannot handle any of the codecs offered in the SDP. Common in interop scenarios.
How to Fix
Check the Warning header or SDP in the response for acceptable parameters. Add compatible codecs (e.g., G.711 as a fallback) to your offer.
Key Differences
301 is a 3xx Redirection response, while 488 is a 4xx Client Failure response.
SIP 301: The user can no longer be found at the address in the Request-URI. The client should direct future requests to the new address in the Contact header.
SIP 488: The request was understood but the session description (SDP) is not acceptable. The response may contain a list of acceptable media parameters.
You encounter 301 when when a user has permanently changed their SIP address. All future calls should be directed to the new URI.
You encounter 488 when when codec negotiation fails — the callee cannot handle any of the codecs offered in the SDP. Common in interop scenarios.
When to Use Which
For 301 (Moved Permanently): Update your address book or routing tables to use the new Contact URI provided in the response. For 488 (Not Acceptable Here): Check the Warning header or SDP in the response for acceptable parameters. Add compatible codecs (e.g., G.711 as a fallback) to your offer.