SIP 183 Session Progress vs 403 Forbidden
SIP 183 (Session Progress) is a 1xx Provisional response, while 403 (Forbidden) 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, 403 means that the server understood the request but is refusing to fulfill it. Authorization will not help. The request should not be repeated.
Descrição
Used to convey information about the progress of the call that is not otherwise classified. Often carries early media (ringback tones, announcements) via SDP.
Quando você o vê
During call setup, especially in PSTN interworking scenarios. The response may contain SDP for early media like custom ringback tones or IVR prompts.
Como corrigir
No fix needed — this is informational. If early media is not playing, check codec negotiation and SDP handling in your UA.
Descrição
The server understood the request but is refusing to fulfill it. Authorization will not help. The request should not be repeated.
Quando você o vê
When the server policy denies the request regardless of credentials. Common for blocked numbers, restricted routes, or ACL violations.
Como corrigir
Check server ACLs and routing policies. Verify the caller is permitted to make this type of call. Contact the server administrator if the block is unexpected.
Diferenças principais
183 is a 1xx Provisional response, while 403 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 403: The server understood the request but is refusing to fulfill it. Authorization will not help. The request should not be repeated.
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 403 when when the server policy denies the request regardless of credentials. Common for blocked numbers, restricted routes, or ACL violations.
Quando usar qual
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 403 (Forbidden): Check server ACLs and routing policies. Verify the caller is permitted to make this type of call. Contact the server administrator if the block is unexpected.