All things related to multicast

["Rich Mavrogeanes" <>]

"Should" is a phrase I use too :)

Experience shows that the issue remains despite TTL settings.
Our default TTL setting is >1 and without a source,  cgmp floods.  I guess
Cisco kows this too, which is why they added the same "work around" in
their IP/TV product.




----- Original Message -----
From: "Toerless Eckert" 
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To: "Richard Mavrogeanes" 
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Cc: 
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Sent: Friday, September 14, 2001 5:16 PM
Subject: Re: Large Multicast Audience


> On Fri, Sep 14, 2001 at 04:45:03PM -0400, Richard Mavrogeanes wrote:
> > Folks,
> >
> > The VBrick can be configured to join its own multicast, and this
> > is the default configuration.  This is because certain poorly designed
> > switches flood (cgmp) if there is not at least one client listening to
> > the multicast.  The feature can be disabled.
>
> This issue by the way only happens if the session has a TTL of 1 on
> the LAN and it's not a limitation of the CGMP switch itself but a
> design choice in the IOS router.
>
> Should never be a problem unless somebody who is sourcing the content
> tries to force this (and other ttl-expiry issues in ip multicast)
> by using too low a TTL in transmission. Operational issues like these
> are unfortunate survivors of a time when people thought TTL scoping is
> a cool idea.
>
> Cheers
> Toerless