Subject: Re: Re: Use of srcmask in prune/grafts

From: Bill Fenner <[email-masked]>
Date: Sat, 22 Jul 2000 00:00:33 -0700

>I think it is not necessary to associate the prune with a route.

Before IGMPv3, the only reason a prune would occur in DVMRP was because
there were no group members at all.  Therefore, it makes sense to prune
the largest unit possible (i.e. the route associated with the source being
pruned).  The netmask was introduced in prunes (and grafts) in order to:

a) ensure that the prune was being applied to the appropriate route
   (especially if you have overlapping routes in your routing table)
b) allow /32 masks to specify source-specific prunes.

  Bill

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From: Mani Manoharan Balaraman <[email-masked]>
Date: Tue, 25 Jul 2000 11:24:18 +0530

Hello

I agre  with what you say with respect to the Pruning in absence of IGMPv3.
However if IGMPv3 is used and if i had to prune a particular source in a
network this will not work if the forwarding cache entry is maintained as
 src net, group ) as mentioned in the dvmrp draft (v3-09) .

Presently dvmrp(v3-09) says that forwarding cache is maintained as (src net,
group) as per Section 2.5.2 (Adding interfaces with neighbors). Suppose i
want to prune a particular source host-group  where is this information
maintained (forwarding cache has srcnet-group and routing table has
srcnet. ) ? I think this is what vijay question is .
In PIM there are separate states maintained for (Src host, G),  (*. G) and
(*, *, RP). But in dvmrpv3, (SrcNet,G) alone is maintained, thus the
question asked by Vijay arises.

Regards,
Mani,
IP team,
WIPRO global R&D.

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From: Bill Fenner <[email-masked]>
Date: Tue, 25 Jul 2000 10:08:10 -0700

The DVMRP spec doesn't specify a specific forwarding cache implementation.

  Bill

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From: Bill Fenner <[email-masked]>
Date: Tue, 25 Jul 2000 21:18:37 -0700

The section you quoted says that initial forwarding is based upon (source
network, group) and that normal prunes are based upon (source network,
group).  It does not specify a (source network, group) forwarding cache.

  Bill

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From: Mani Manoharan Balaraman <[email-masked]>
Date: Wed, 26 Jul 2000 09:50:50 +0530

Hello

The following section from the dvmrp draft (v3-09) indiccates that the
forwarding cache entry should be based on (src net, Group)

2.5.2.  Adding Interfaces with Neighbors
   Initially, all interfaces with downstream dependent neighbors should
   be included in the downstream interface list when a forwarding cache
   entry is first created.  This allows the downstream routers to be
   aware of traffic destined for a particular (source network, group) pair.
The
   downstream routers will then have the option to send prunes
   and subsequent grafts for this (source network, group) pair as
   requirements change from their respective downstream routers and
   local group members.

Mani

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From: Mani Manoharan Balaraman <[email-masked]>
Date: Wed, 26 Jul 2000 10:14:01 +0530

Hello

This section also says the forwarding cache entry is created with
sourcenetwork-group pair. Is it  that initially the forwarding cache will be
created with (src net-group) but later modified to (src host-group) ?

Thanks
Mani