Subject: (PIM-SM) processing of received assert message

From: "bhavesh pathak" <[email-masked]>
Date: Sun, 17 Oct 1999 05:34:40 PDT

Dear everyone,

a.
When assert message is received on the outgoing interface,
longest match is used to match with the entry, but if the
^^^^^^^
assert message is received on the incoming interface exact
                                                     ^^^^^
match is enforced.

Why such a difference?

b. "Receiving Asserts on an entry's incoming interface" section
    says that,

    2 If the downstream routers have downstream members, and if
      the Assert caused the RPF neighbor to change, the downstream
      routers must trigger a Join/Prune message to inform the upstream
      router that packets are to be forwarded on the multi-access
      network.

               upR1          upR2  (upstream router)
                 |             |
            ----------------------- LAN
                 |             | (incoming interface)
                 downR1        downR2 (downstream routers)
                               |
                               |
                            ---------
                               |
                               downdownR1

   Here, when downR2 receives assert message in the incoming
   interface. It means that,
   - there is a contention between upR1 and upR2 regarding who
     should forward the multicast data to LAN.
   - after assert related processing gets compeleted one of upR1
     or upR2 will be responsible to forward the traffic on LAN.

If above is correct, then downR2 will be able to recieve multicast
data even without sending join/prune message towards upstream
neighbor.

So, I am not able to understand why does downR2 MUST send
send Join/Prune towards upstream neighbour?

with regards,
bhavesh

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