SIP 204 No Notification vs 401 Unauthorized
SIP 204 (No Notification) is a 2xx Success response, while 401 (Unauthorized) is a 4xx Client Failure response. 204 indicates that the request was successful but the server has decided not to send a NOTIFY for this SUBSCRIBE request. In contrast, 401 means that the request requires user authentication. The response includes a WWW-Authenticate header with a challenge for the realm.
Description
The request was successful but the server has decided not to send a NOTIFY for this SUBSCRIBE request.
When You See It
When subscribing to event packages that may not generate immediate notifications, such as dialog or presence packages.
How to Fix
No fix needed. The subscription was accepted but there is no state change to notify about yet.
Description
The request requires user authentication. The response includes a WWW-Authenticate header with a challenge for the realm.
When You See It
When making a request that requires Digest authentication. Common for REGISTER and INVITE requests to authenticated SIP trunks.
How to Fix
Resend the request with proper Authorization header containing valid credentials (Digest authentication).
Key Differences
204 is a 2xx Success response, while 401 is a 4xx Client Failure response.
SIP 204: The request was successful but the server has decided not to send a NOTIFY for this SUBSCRIBE request.
SIP 401: The request requires user authentication. The response includes a WWW-Authenticate header with a challenge for the realm.
You encounter 204 when when subscribing to event packages that may not generate immediate notifications, such as dialog or presence packages.
You encounter 401 when when making a request that requires Digest authentication. Common for REGISTER and INVITE requests to authenticated SIP trunks.
When to Use Which
For 204 (No Notification): No fix needed. The subscription was accepted but there is no state change to notify about yet. For 401 (Unauthorized): Resend the request with proper Authorization header containing valid credentials (Digest authentication).