SIP 100 Trying vs 183 Session Progress
Both SIP 100 (Trying) and 183 (Session Progress) belong to the 1xx Provisional category. 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. Meanwhile, 183 means 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.
描述
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.
何时出现
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.
如何修复
No fix needed — this is normal call setup behavior. If stuck on 100 Trying for too long, check network connectivity and proxy configuration.
描述
Used to convey information about the progress of the call that is not otherwise classified. Often carries early media (ringback tones, announcements) via SDP.
何时出现
During call setup, especially in PSTN interworking scenarios. The response may contain SDP for early media like custom ringback tones or IVR prompts.
如何修复
No fix needed — this is informational. If early media is not playing, check codec negotiation and SDP handling in your UA.
主要区别
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 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.
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 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.
何时使用哪个
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 183 (Session Progress): No fix needed — this is informational. If early media is not playing, check codec negotiation and SDP handling in your UA.