In the SIP response codes some responses indicate a failure :
● 4xx indicating a Client Failure Response
● 5xx indicating a Server Failure Response
● 6xx indicating a Global Failure Response
When one these 4xx, 5xx or 6xx responses occurs then the corresponding flow is entered in the Errors table.
Following response codes are excluded since they do not indicate real errors :
● 401 Unauthorized
● 403 Forbidden
● 407 Proxy Authentication
● 486 Busy Here
● 487 Request Terminated
Per SIP method there is a tab indicating the Errors in the message flows.
An Error table for a SIP INVITE looks as follows :
Selecting the link indicated above in the red box brings up the corresponding SIP message flow :
In this ladder diagram the Error Response code is immediately visible as it is emphasized in red.