Metro Ethernet Multicast Support

Nathan Ward nanog at
Wed Nov 5 00:15:44 UTC 2008

On 5/11/2008, at 9:13 AM, Holmes,David A wrote:

> The Metro Ethernet Forum (MEF) MEF10-1 ELAN multipoint-to-multipoint
> specification says that multicast packets must be replicated out all
> ports in the ELAN, except the ingress port. Some carriers have taken
> this literally and built a virtual ELAN service emulating a 1990's  
> style
> hub in which all multicast packets are replicated out all ports
> regardless of the L3 multicast routing protocol in use. In the case of
> PIM sparse mode real physical Ethernet switches use IGMP snooping to
> construct a directed path through the switch fabric, so that a given
> established multicast stream is forwarded just like a directed unicast
> connection with mac/port table entries establishing a single path
> through the L2 fabric, and no flooding is done. Some carriers flood
> directed multicast traffic out all ELAN ports even though a single  
> path
> should be taken. In networks with a large number of directed multicast
> streams, flooding out all ports uses unnecessary bandwidth, sometimes
> rendering a 10 Mb port useless due to oversubscription caused by this
> unnecessary flooding.
> Can anyone suggest a carrier MEF ELAN multipoint-to-multipoint service
> that does not flood established directed PIM sparse mode streams?

Are you looking for a vendor product, or a service?

I'm not aware of any vendor products or services that do what you  

However, I'd recommend perhaps a L3 VPN service with multicast support  
and pushing your mcast traffic down it, perhaps talk to your L2  
service provider and see if they can provide you with this in parallel  
to your L2 service.

Nathan Ward

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