SIP 100 Trying vs 493 Undecipherable
SIP 100 (Trying) is a 1xx Provisional response, while 493 (Undecipherable) is a 4xx Client 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, 493 means that the request body was encrypted with S/MIME but the server cannot decrypt it. The server may lack the necessary key or certificate.
Descrição
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.
Quando você o vê
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.
Como corrigir
No fix needed — this is normal call setup behavior. If stuck on 100 Trying for too long, check network connectivity and proxy configuration.
Descrição
The request body was encrypted with S/MIME but the server cannot decrypt it. The server may lack the necessary key or certificate.
Quando você o vê
When using S/MIME encryption for SIP message bodies and the recipient does not have the corresponding decryption key.
Como corrigir
Ensure the recipient has the correct S/MIME certificate and private key. Consider using TLS for transport-layer encryption instead.
Diferenças principais
100 is a 1xx Provisional response, while 493 is a 4xx Client 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 493: The request body was encrypted with S/MIME but the server cannot decrypt it. The server may lack the necessary key or certificate.
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 493 when when using S/MIME encryption for SIP message bodies and the recipient does not have the corresponding decryption key.
Quando usar qual
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 493 (Undecipherable): Ensure the recipient has the correct S/MIME certificate and private key. Consider using TLS for transport-layer encryption instead.