ANSWER(312) with billsec 0

Sometimes there is CDR with ANSWER disposition, HGC 312 and billsec 0s.

How to interpret this case?

The following example will illustrate one such case.

The call flow is from the Origination Point (OP) to the Proxy, Proxy sends the call over Freeswitch (FS), then back through the Proxy to the Termination Point.

In short: OP -> Proxy -> FS -> Proxy -> TP

We have the following schema:

OP sends the CANCEL at the time: 10:32:54.507296 and TP sends the ANSWER at the 10:32:54.506003. The difference is 0.0001293 seconds.

In this case