SIP 183 Session Progress vs 608 Rejected
SIP 183 (Session Progress) is a 1xx Provisional response, while 608 (Rejected) is a 6xx Global 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, 608 means that an intermediary machine or process rejected the call attempt. Similar to 607 but the rejection comes from the network rather than the end user.
Description
Used to convey information about the progress of the call that is not otherwise classified. Often carries early media (ringback tones, announcements) via SDP.
When You See It
During call setup, especially in PSTN interworking scenarios. The response may contain SDP for early media like custom ringback tones or IVR prompts.
How to Fix
No fix needed — this is informational. If early media is not playing, check codec negotiation and SDP handling in your UA.
Description
An intermediary machine or process rejected the call attempt. Similar to 607 but the rejection comes from the network rather than the end user.
When You See It
When a network element (not the callee) blocks the call. Used by analytics engines and call-blocking services in the network path.
How to Fix
This is a network-level block. Contact the network administrator or carrier to understand why the call was blocked.
Key Differences
183 is a 1xx Provisional response, while 608 is a 6xx Global 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 608: An intermediary machine or process rejected the call attempt. Similar to 607 but the rejection comes from the network rather than the end user.
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 608 when when a network element (not the callee) blocks the call. Used by analytics engines and call-blocking services in the network path.
When to Use Which
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 608 (Rejected): This is a network-level block. Contact the network administrator or carrier to understand why the call was blocked.