WAN Ethernet - Multicast

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May 2nd, 2007
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Could someone explain how multicast traffic is handled for specific customer in carrier network . The Main office and remote offices are connected via L2 Ethernet service.

The question I have is since WAN ethernet is shared medium once my multicast traffic is get into the carrier network how they handle the multicast traffic.

1.Should all the customers will receive the multicast traffic? OR

2.Somehow the traffic will be routed to my remote offices only by the carrier. How they do ?

3. Do I need to ask carrier any specific questions regarding Multicast when I subscribe WAN Ethernet service.

Thank you,

Raja Ramasamy

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Overall Rating: 5 (1 ratings)
swaroop.potdar Wed, 05/02/2007 - 19:42
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When you subscribe for a L2 Ethernet (ATOM) service, the service provider only deals with transporting the received frames on the Layer2 interface from your CE from one end to the other end.

The Service Provider does not maintain any multicast state information for your multicast traffic for your L2 VPN.

So for him all you packets received IPV4, IPV6 or Multicast look alike (Frames).

Although its a little different for L3VPN's.



rramasam04 Tue, 06/05/2007 - 03:21
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Thanks Swaroop. If you could explain how multicast traffic is handled in L3VPN that would be great.



swaroop.potdar Tue, 06/05/2007 - 05:43
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Raja, the MVPN concept in L3VPN needs the SP backbone to be multicast enabled in contrast to L2VPN, where the multicst traffic is switched as any other traffic.

For idea behind MVPN in MPLS is to encapsulate VPN multicast packets into a multicast GRE tunnel which connects all the PE's where this VRF termiates. (this is controlled by the Default MDT configuration).

So essentially you build a backbone within a backbone for your end customer.

When the backbone is in place via default MDT, to enhance traffic forwarding to only intrested receivers and not to all end points, data MDT is put in place which forwards traffic between a source and intrested destinations. (this can be configured to trigger when a certain data threshold is crossed using the default MDT path for multicast traffic)

Here is a neat white paper with illustrations for reference.





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