Subject: [pim] Abt : PIM DM periodic nature

From: "Rajib" <[email-masked]>
Date: Mon, 19 Apr 2004 23:57:58 -0400

Hi,

I will be very happy if someone spare some time and give me some suggestions on the following issue.

As per PIM DM- 

Prune state has a finite lifetime.  When that lifetime expires, data will again be forwarded down the previously pruned branch.

In order to minimize repeated flooding of packets and subsequent pruning associated with a particular (S,G) pair, PIM-DM uses a state 
refresh message.  This message is sent by the router(s) directly  connected to the source and is propagated throughout the network.  When
received by a router on its RPF interface, the state refresh message causes an existing prune state to be refreshed.

1. My question is what was reason of  giving finite lifetime to Prune ? 

2. In the version 2 it was overcome by the state refresh message. It seems that version1 was wrong and version 2 corrects it without making any major change in the protocol. Why not any major change like the following ways-

What I am proposing-

1. There will be no periodic timer enable in any router except for the router directly connected to the source. I mean, when a router gets any data from it's directly connected  source (not from any other router) only then it will enable a timer for that particualar (S,G).

2.  When a particular (S,G) state is created in all routers after arriving multicast data. This (S,G) state for a particular source and group will not timeout and hence will not be deleted unless the router gets and proposed "Multicast session end" message from the router directly connected to the sender.

3. Pruned branches will never timeout. These pruned branches will only become active "Dense" when they get grafts.While the multicast session is in process.

4. When there is no (S,G) data (data for particular source and group) from the source to directly connected router, for more than a particular time (say 6  minutes) then this router will assume that the source has finished or discontinued the session and the router will flood the proposed "Multicast session end" message for particular (S,G) through out the network and all those particular (S,G) states in differnet routers will be deleted.

These make the protocol-

1. Very simple.

2.Makes the protocol suitable for both dense and sparse mode.

3. No unnecessary timers in routers.

4. No periodic flooding.

5.No concern regarding prune or any other thing time out. 

I know my proposal goes far away from PIM DM. But it is PIM DM based. Is it ok to use ? 

I will be very happy if you please let me know is there any problem with my proposal. 

Rajib Bashir