All things related to multicast

[Bill Nickless <>]

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At 06:26 PM 10/9/2000 -0400, Bill Owens wrote:
>The big question, though, is whether it would work at all. Has anyone 
>tried this sort of thing? Does it seem to make sense?
>
>Thanks for any help you can provide,
>Bill.

Yes, the plan you laid out can be made to work.

However, if you're going to go to the trouble of running M-BGP and PIM-SM 
everywhere, I am confused as to what you gain by NOT running MSDP.  You're 
already accepting the burden of PIM-SM protocol operation, which means a 
relatively late version of router code.  You're already accepting the 
burden of M-BGP, which means an additional requirement for memory 
(proportional to the number of NLRI=Multicast routes) in each of your 
routers.  And with both of those you're already accepting a requirement for 
configuration tasks in your backbone core and at each of your customer sites.

MSDP generally means about 5 extra configuration lines, a couple of access 
lists, and a small amount of memory (proportional to the number of active 
sources) in each of your routers.

The most immediate downside that I can see is that you're stuck with a 
single RP for all of your customers.  Problems related to 
single-point-of-failure come immediately to mind.  Without thinking too 
hard about it, I'm afraid you'll have to manually(?) maintain some ugly 
access control lists so your RP knows what prefixes it should advertise.

Getting an RP to generate MSDP SAs depends on the PIM Designated Router on 
the directly attached LIS to send PIM Register packets towards the 
RP.  Sometimes the PIM DR stops doing this [known bug in Cisco IOS 
<12.0(10)].  The configuration you outline makes this problem much harder 
to solve, since the problem of MSDP SA generation could be inside your 
backbone or at your customer site.  By asking your customers to run MSDP, 
the question your NOC asks is simple: are they originating MSDP SAs or 
not?  If so, then the problem is yours.  If not, then the problem is at 
your customer site.

By accepting MSDP and PIM-SM, I think you're 90% of the way to your 
finished solution.  My personal opinion is that the extra 10% of effort to 
fully deploy MSDP will be less than the effort necessary to implement your 
outlined solution.

#include <sodium_chloride_crystal.h>

Hope this helps,
===
Bill Nickless    http://www.mcs.anl.gov/people/nickless      +1 630 252 7390
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