[j-nsp] P2MP LSP

[Mark Tinka]

On Wednesday 30 June 2010 03:18:34 am David water wrote:

> Using those route types we can communicate about the
>  source and destinations in MVPN.

Source information is learned by the Sender PE router. This 
can either be through the VPN C-RP infrastructure or MSDP.

Receiver PE routers would then use this information to 
generate Type 5 Source Active AD (Auto-discovery) routes. 
These routes allow the Receiver PE routers to identify 
active Multicast sources.

Ideally (I say ideally because we had some nasty bugs in our 
case), this would then lead to the generation of Type 7 
Source Tree Join routes on the Receiver PE routers, assuming 
the router learns of C-join information, e.g., static IGMP 
configuration, or has a Type 6 Shared Tree Join route and 
receives a Type 5 route.

You can reference this entire process in the documents I 
sent you earlier.

>  Now as we know how to
>  discover the source and receiver its time for RSVP to
>  take care of building the P2MP right?

It doesn't necessarily happen in this sequence.

P-tunnel setup, i.e., association of a p2mp LSP with the RSI 
carrying MCAST-VPN NLRI would be part of your standard 
configuration when implementing BGP/MPLS NG-MVPN's.

The PMSI attribute allows the P-tunnel to be announced in 
the network via BGP. When the Receiver PE routers receive 
this information, they bind the P-tunnel to the correct RSI 
that imported it. Once the P-tunnel is bound to the right 
RSI, the Receiver PE router can forward the Multicast 
traffic into the local VRF, using MPLS.

Again, see those documents I sent. They get into very good 
detail about the process.

>  So RSVP does use
>  the the BGP discovered information to establish LSP,
>  correct? So this way LSPs are totally dynamic.

Not quite - the p2mp LSP's are setup by hand. BGP is just 
used to distribute control plane information about Multicast 
routing data. Once the control plane provides sufficient 
information, traffic is forwarded down the pre-setup p2mp 
LSP's (MPLS data plane).

If you're looking at dynamic p2mp LSP setup, consider mLDP 
(Multicast LDP). Like in regular LDP for unicast 
applications, it's dynamic.

I don't have any solid details yet on Juniper's plans re: 
mLDP, but I know Cisco are pushing this very heavily, along 
with some other options to using BGP as a replacement for 
PIM.

Good times ahead between Juniper and Cisco, in this space 
:-).

Cheers,

Mark.
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