From: Brian McGahan (bmcgahan@internetworkexpert.com)
Date: Wed May 30 2007 - 12:39:50 ART
> SSM can run on a sparse-mode network. It only needs to be enabled on
the
> last-hop routers.
SSM requires PIM to run in sparse mode, and SSM must be enabled
everywhere in the transit path from the server to the client.
With traditional sparse mode all traffic uses a shared tree that
is rooted at the RP. This means that when a client wants to join a
group the PIM Sparse Join message is forwarded up the RPF tree towards
the RP. With SSM all trees are source based trees, hence the PIM Sparse
Join messages are sent up the RPF tree to the source, not the RP. This
implies that everyone in the transit path must support the sending of
(S,G) Join messages for SSM instead of (*,G) joins for normal RP rooted
shared trees.
Kim I would highly recommend this book if you really want to
understand how the different PIM modes interoperate and how advanced
topics such as SSM and MSDP work:
http://www.amazon.com/Interdomain-Multicast-Routing-Practical-Solutions/
dp/0201746123. It's also available on safari online if you have a
subscription.
HTH,
Brian McGahan, CCIE #8593 (R&S/SP)
bmcgahan@internetworkexpert.com
Internetwork Expert, Inc.
http://www.InternetworkExpert.com
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-----Original Message-----
From: nobody@groupstudy.com [mailto:nobody@groupstudy.com] On Behalf Of
Vince Mashburn
Sent: Wednesday, May 30, 2007 10:16 AM
To: Ivan
Cc: ccielab@groupstudy.com; Kim
Subject: Re: ip pim sparse-mode vs. ip pim ssm
SSM needs a (S,G) entry in order to forward any traffic. So, a
multicast
group is no longer identifed by IP addresses in the 224.0.0.0 -
239.255.255.255 range. Using SSM it is defined to be any souce plus the
multicast address combo. In sparse mode, all you need is a group
address
and a RP. SSM does 2 things for you.
1) it expands the multicast addressing range becasue (1.1.1.1,
225.1.1.1)
can potentially be a different stream than (2.2.2.2, 225.1.1.1)
2) it allows multicast routing between domains as long as you have a
route
to the source.
SSM can run on a sparse-mode network. It only needs to be enabled on
the
last-hop routers.
Hope this helps.
On 5/30/07, Ivan <ivan@iip.net> wrote:
>
> ssm can accept flow only from defined source.
> ssm don't need RP.
>
> On Wednesday 30 May 2007 17:51, Kim wrote:
> > Hello all,
> > I am reading the multicast DocCD
> >
>
http://www.cisco.com/univercd/cc/td/doc/product/software/ios124/124cg/hi
mc_
> >c/chap05/mcbbasic.htm. Can someone explain or point me to more
resources
> > about ip pim sparse-mode vs. ip pim ssm? I can't tell any big
> difference.
> >
> > Thanks.
>
>
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