SIP 183 Session Progress vs 493 Undecipherable
SIP 183 (Session Progress) is a 1xx Provisional response, while 493 (Undecipherable) is a 4xx Client Failure response. 183 indicates that used to convey information about the progress of the call that is not otherwise classified. Often carries early media (ringback tones, announcements) via SDP. 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.
Описание
Used to convey information about the progress of the call that is not otherwise classified. Often carries early media (ringback tones, announcements) via SDP.
Когда вы это видите
During call setup, especially in PSTN interworking scenarios. The response may contain SDP for early media like custom ringback tones or IVR prompts.
Как исправить
No fix needed — this is informational. If early media is not playing, check codec negotiation and SDP handling in your UA.
Описание
The request body was encrypted with S/MIME but the server cannot decrypt it. The server may lack the necessary key or certificate.
Когда вы это видите
When using S/MIME encryption for SIP message bodies and the recipient does not have the corresponding decryption key.
Как исправить
Ensure the recipient has the correct S/MIME certificate and private key. Consider using TLS for transport-layer encryption instead.
Ключевые различия
183 is a 1xx Provisional response, while 493 is a 4xx Client Failure response.
SIP 183: Used to convey information about the progress of the call that is not otherwise classified. Often carries early media (ringback tones, announcements) via SDP.
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 183 when during call setup, especially in PSTN interworking scenarios. The response may contain SDP for early media like custom ringback tones or IVR prompts.
You encounter 493 when when using S/MIME encryption for SIP message bodies and the recipient does not have the corresponding decryption key.
Когда что использовать
For 183 (Session Progress): No fix needed — this is informational. If early media is not playing, check codec negotiation and SDP handling in your UA. For 493 (Undecipherable): Ensure the recipient has the correct S/MIME certificate and private key. Consider using TLS for transport-layer encryption instead.