I'm missing a piece of the puzzle with this switchover, in step 3 of the
SPT-Switchover process, why is the router waiting 1 second before joining the
SPT? If the multicast packets are still coming from the RP why would a packet
come in from another source? Aren't all sources going to be the RP?
SPT-Switchover process (from Beau Williamson book page 282 - 284):
1)Group G rate exceeds SPT-Threshold
2)Then the router sets the J flag in (*,G) entry to indicate that a switch to
the SPT is in order and waits for the next (Sx,G) packet
3)Next (Sx,G) packet is received from the shared tree. The router then checks
the (*,G) entry and sees that the J flag is set, which indicates that a switch
to the SPT-Threshold is in order.
The router then temporarily resets the J flag until the next measurement
interval. This action prevents more than one source from being switched to the
SPT until the 1-second measurement interval is run again after switching this
source to the SPT.
4)router then creates (Sx,G) state and sends an (Sx,G) Join toward teh source
to join the SPT for this source.
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