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