[AG-TECH] IGMPv3, Source Specific Multicast, fully supported in Windows XP

Jeffrey Eschbach eschbach at motorola.com
Fri Aug 16 10:49:30 CDT 2002

Well I'll take a stab at this... Bill or anyone else, feel free to add
to my reply (and correct any errors :).

> Three sites, Foo, Bar, and Nee.  All are sending multicast data to the
> same routable multicast group address.

First off, I think it's important to know if your group address is
within the SSM range or not (typically  You will have
different behavior if you use this SSM range versus the remaining ASM
range.  I'll assume the SSM range and therefore no Rendezvous Point
involvement for my reply.

> Foo sends a SSM request to only get traffic from Bar.  Are the following
> true?
> If Bar's edge devices support IGMPv3, no effect since it's traffic is
> being requested.

OK... Bar's traffic will go to Foo.

> If Nee's edge devices support IGMPv3 and Foo is the only requestor, then
> the traffic won't leave Nee's network.  If Nee's edge doesn't support
> IGMPv3, the traffic will go onto the backbone.

No traffic should enter the backbone if sending to an SSM address if no
receivers have joined.  I don't think IGMPv3 actually is involved on the
source side... the router just needs to know that it should not forward
traffic in the SSM range unless it has received a join.  (For ASM range,
traffic would go to the RP and then receive a "register stop" to keep
the traffic from leaving the network.)

> If Foo's edge devices support IGMPv3, then Nee's traffic will be
> filtered at the Edge and will not reach Foo.

OK (but see previous answer).

> If the edge router for each site supports IGMPv3, if the goal is
> reducing traffic over the backbone and across the Internet2 POP, does it
> matter if the switches behind the edge router support IGMPv3?

I don't think so, as long as your edge device supported IGMPv3.

Hope that helped,

> -----Original Message-----
> From: Bill Nickless [mailto:nickless at mcs.anl.gov]
> Sent: Thursday, August 15, 2002 10:36 PM
> To: Jay Beavers
> Cc: ag-tech at accessgrid.org
> Subject: Re: [AG-TECH] IGMPv3, Source Specific Multicast, fully
> supported in Windows XP
> At 10:01 PM 8/15/2002 -0700, Jay Beavers wrote:
> >Since I'm not a router bithead, can anyone give me a heads up if I
> should
> >expect SSM to "just work" between Internet2 nodes?  Or might there be
> >complications?
> Hi Jay,
> To answer your specific question: the Internet2 Abilene network is ready
> and capable of running SSM, and has been for well over a year.
> That being said, the problem with SSM deployment revolves around the
> need
> for network edge devices like switches and routers to support IGMPv3.
> It's
> difficult to find Ethernet switches that support IGMPv3, and they're not
> the most economical choices.
> In a strange inversion of the normal situation, the backbone is capable
> of
> SSM service well before the local area networks of the connected sites.
> If
> you can find a site that supports SSM/IGMPv3 locally, it's a pretty good
> bet that they can do SSM with most all other similar sites.
> ===
> Bill Nickless    http://www.mcs.anl.gov/people/nickless      +1 630 252
> 7390
> PGP:0E 0F 16 80 C5 B1 69 52 E1 44 1A A5 0E 1B 74 F7
> nickless at mcs.anl.gov

Jeff Eschbach                              eschbach at motorola.com
Networks and Infrastructure Research
Senior Staff Engineer, Motorola Labs Internet2 Initiative
http://internet2.motlabs.com              Fax:    (847) 576-3240
Desk: (847) 538-5846                      Mobile: (847) 980-2240

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