* Use 32-bit time stamp to get reference time stamp on a switch.
With relay and dyncast and migration, it is possible that different
layers of a simulcast get out of sync in terms of extended type,
i. e. layer 0 could keep running and its timestamp could have
wrapped around and bumped the extended timestamp. But, another layer
could start and stop.
One possible solution is sending the extended timestamp across relay.
But, that breaks down during migration if publisher has started afresh.
Subscriber could still be using extended range.
So, use 32-bit timestamp to infer reference timestamp and patch it with
expected extended time stamp to derive the extended reference.
* use calculated value
* make it test friendly
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