Mark Tinka mtinka at globaltransit.net
Thu Dec 29 10:03:20 UTC 2011

On Thursday, December 29, 2011 08:02:04 AM Keegan Holley 

> Isn't source discovery and efficiency a big concern for
> ASM?  If individual streams are tied to a specific
> source then it's possible to live without some of the
> overhead involved in ASM.  Joins go straight to the
> source, traffic is disseminated via direct paths instead
> of being replicated by the RP, etc etc..

In our case, Source discovery happens once, and BGP updates 
containing that information is sent to all Receiver PE 
routers in the MVPN.

They then generate Type 7 routes locally (due to running 
SPT-only mode), which are essentially (S,G) routes.

Once a customer sends a Join message to subscribe to a 
group, the Receiver PE router just serves it locally. No 
need to send any requests back to the RP.

This breaks regular PIM mechanisms, but is a welcome 
deviation that makes a lot of sense.

One does have the option of running RPT-SPT modes which are 
akin to regular IP Multicast.

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