[j-nsp] Multicast without tunnel pic

Harry Reynolds harry at juniper.net
Tue Jul 18 19:26:51 EDT 2006

Your understanding is largely correct. The first hop PIM router (the DR I believe) encapsulates mcast traffic into register messages (makes use of the TP), for unicast transmission to the RP, which then decapsulates (also uses TP) and sends as native mcast down the shared tree. Once the receiver joins the SPT for that sender, the first hop router will generally get a register stop from the RP (assumes no more listeners for that source on the shared tree), and you will have native mcast flowing between sender and receiver over the SPT with no more register encapsulation. 

A TP is not needed for a PIM router that has only receivers attached and is not acting as an RP. As I understand a TP is *not* needed in PIM-SM with M/T boxes, when the first hop router is *also* the RP. However, note that if you have remote senders also using that RP, it will need a TP in order to perform register message decapsulation.


> -----Original Message-----
> From: juniper-nsp-bounces at puck.nether.net 
> [mailto:juniper-nsp-bounces at puck.nether.net] On Behalf Of 
> Raniery Pontes
> Sent: Tuesday, July 18, 2006 4:07 PM
> To: juniper-nsp at puck.nether.net
> Subject: [j-nsp] Multicast without tunnel pic
> Hi,
>  we´ve got some M320´s configured to run multicast 
> (IGMP+PIM-SM). There is also a static Rendeszvous Point 
> running on a Cisco router.
> AFAIK, when multicast distribution trees are built, there are 
> some steps where packet encapsulation is needed. But I 
> believe it only happens with traffic from multicast *sources* 
> and not multicast *receivers* (which only need to send IGMP joins).
> Then my question is:  Is it possible to run multicast sources 
> and/or multicast receivers connected directly to these 
> routers, without a tunnel PIC?
> I guess only receivers would work in this scenario, but I´d 
> like to know your opinion.
> Thanks
> Raniery
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