SIP 100 Trying vs 580 Precondition Failure
SIP 100 (Trying) is a 1xx Provisional response, while 580 (Precondition Failure) is a 5xx Server Failure response. 100 indicates that the request has been received by the next-hop server and an unspecified action is being taken to process it. The UAC should expect additional responses. In contrast, 580 means that the server is unable or unwilling to meet some of the preconditions specified in the request for resource reservation.
Description
The request has been received by the next-hop server and an unspecified action is being taken to process it. The UAC should expect additional responses.
When You See It
Immediately after sending an INVITE. The proxy has received the call and is searching for the callee. This is the SIP equivalent of a dial tone.
How to Fix
No fix needed — this is normal call setup behavior. If stuck on 100 Trying for too long, check network connectivity and proxy configuration.
Description
The server is unable or unwilling to meet some of the preconditions specified in the request for resource reservation.
When You See It
When using QoS preconditions (RFC 3312) and the network cannot guarantee the required quality of service for the media session.
How to Fix
Relax the precondition requirements or ensure the network path supports the required QoS. Consider removing precondition requirements for best-effort calls.
Key Differences
100 is a 1xx Provisional response, while 580 is a 5xx Server Failure response.
SIP 100: The request has been received by the next-hop server and an unspecified action is being taken to process it. The UAC should expect additional responses.
SIP 580: The server is unable or unwilling to meet some of the preconditions specified in the request for resource reservation.
You encounter 100 when immediately after sending an INVITE. The proxy has received the call and is searching for the callee. This is the SIP equivalent of a dial tone.
You encounter 580 when when using QoS preconditions (RFC 3312) and the network cannot guarantee the required quality of service for the media session.
When to Use Which
For 100 (Trying): No fix needed — this is normal call setup behavior. If stuck on 100 Trying for too long, check network connectivity and proxy configuration. For 580 (Precondition Failure): Relax the precondition requirements or ensure the network path supports the required QoS. Consider removing precondition requirements for best-effort calls.