Subject: Re: MBone loops ?

From: Cyndi Jung <[email-masked]>
Date: Fri, 26 Sep 1997 10:38:20 -0700

You shouldn't get loops, but versions of mrouted older the the
very most recent one will fail to prune, which would cause an
undue burden on all the routers upstream.  The failure to prune 
is because the older versions of mrouted required a prune from ALL
neighboring routers, but should have only required prunes from 
those that were downstream from them with respect to a given source 
subnet, based on poison-reverse in the DVMRP updates.  In the picture 
below, if Rout3 and Rout4 have the same metric back to a given 
source subnet, and Rout3 wins the tie breaker and becomes the forwarder
for multicast sourced from that subnet, Rout4 will never prune to
Rout3 (his reverse path is via Rout2), and this is bad.

Run the latest mrouted.

Cyndi

At 03:01 AM 9/26/97 -0300, Joao Carlos Mendes Luis wrote:
>Hi,
>
>  I'm just thinking, is it possible to create loops to the MBone,
>in order to get redundancy ?
>
>  For example:
>
>
> +--------------------------------------------------------+
> |                      MBone cloud                       |
> +-------+---------------------------------+--------------+
>         |                                 |
>     +---+---+                         +---+---+
>     | Rout1 |                         | Rout2 |
>     +---+---+                         +---+---+
>         |                                 |
>     +---+---+                         +---+---+
>     | Rout3 |                         | Rout4 |
>     +---+---+                         +---+---+
>         |                                 |
>         +---------------------------------+
>
>  Would it work efficiently, or would all traffic come from
>both interfaces ?  It seems to me that pruning only is not
>designed to work this way, but I don't know other features
>of DVMRP.
>
>					Jonny
>
>--
>Joao Carlos Mendes Luis			[email-masked]
>+55 21 290-4698				[email-masked]
>Universidade Federal do Rio de Janeiro	UFRJ/COPPE/CISI
>PGP fingerprint: 29 C0 50 B9 B6 3E 58 F2  83 5F E3 26 BF 0F EA 67
>
>