[SR-Users] difference in INVITEs when failure_route applies

[Grant Bagdasarian]

Hello,

Consider the following: the Dispatcher module has two destinations loaded.

Now let's say we have the following two scenarios:

Scenario 1:
Kamailio tries to relay the INVITE to the first destination selected by the Dispatcher module, but this destination does not reply for some reason.

Scenario 2:
Kamailio tries to relay the INVITE to the first destination selected by the Dispatcher module, but this destination replies back with a 500 Server Internal Error.

I know that in the first case, Kamailio will enter the failure_route and try to Dispatch the INIVTE to the next destination in the set.
In the second case, I'm not sure, because this would require some custom code to drop the 500 reply and try the next destination in the Dispatcher set. Correct?

If the second case solution is possible and Kamailio tries the next  destination, which values would make the second INVITE and its replies different from the first INVITE and its replies?
The To-Tag and CSeq should be different right? Any other values which Kamailio perhaps uses internally to identify/associate messages? Are these values accessible?

The reason I'm asking this is because I want to log each INVITE tried as a separate call in our database and use SIP replies and in-dialog requests to update its state, but I'm doing this based on the CallID.
For this to work, I need another value to make each INVITE (which have the same CallID, in case of Failover) unique.
The requirements are that these values must be present for each message in a dialog.

I hope I'm being clear enough.

Regards,

Grant
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