Wednesday, December 3, 2008

Basics of MVPN

We are using ip multicast in the service provider network. But what about those service provider which are running MPLS. MVPN (Multicast VPN) is the one which is being deployed by service provider to transport customer multicast traffic over mpls backbone. Every customer is coming over ip cloud and has their unique multicast domain. For that domain customer wants to transport the multicast routing information along with rp information to another locations. Service provider MVPN network is responsible for forwarding customer multicast packets to another locations. All the multicast packets encapsulate at PE end and again de encapsulate at other PE end.

Now the hitch comes how the packet will encapsulate. For this we have concept of default mdt and data mdt. Default mdt is responsible for establishing multicast tunnel across all PE and should be unique per vpn. Data mdt is used for stopping unwanted multicast traffic across PEs. So we can say we have two multicast domain one is purely for customers and another is purely for service provider network. Remember one thing latter will be used for the reachability of default mdt. For example if we having a customer and default mdt is being defined, lets say i.e. For the reachability of we use the pim in service provider core. Now the next question comes in mind what should be the protocol in core because we have to forward the information of default mdt. Can we use auto-rp,bsr or ssm? Auto-rp, BSR is quite a good pim protocol but what will happen if we choose SSM? SSM requires IGMPv3 so don't implement SSM in core. Here most of time we are wrong because we are implementing SSM for default MDT group transportation not for multicast. So no need to worry you can implement SSM in the core. (SSM doesn’t require RP in the network)

So MVPN requires
PIM routing protocol in the SP core.
Default MDT and Data MDT (Default MDT is mandatory & Data MDT is not mandatory)

shivlu jain

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