All things related to multicast

[David Farmer <>]

I propose that general purpose classic IPv4 ASM be deprecated on the Internet2 R&E Backbone. The primary propose of this change is to simplify multicast support for the new MPLS based R&E Backbone, by mostly eliminating the need for MSDP. SSM for both IPv4 and IPv6, and Embedded-RP for IPv6, should continue to be supported on the Internet2 R&E Backbone, as they do not require MSDP. 

Requests for legacy support of classic IPv4 ASM on a per-group basis over the R&E Backbone to a defined sets of Connectors and/or Participants should be considered for meritorious applications. This would provide provide a safety-net for any truly deserving applications, while highly limiting the scope for any continued use of MSDP on the R&E Backbone.  With this highly limited scope the MPLS VRF issues discussed below should be containable.

Further, any Connectors and/or Participants that wish to continue to support classic IPv4 ASM using MSDP on a general basis could do so by directly peering across AL2S point-to-point VLANs. Or, if there were sufficient interest in continued use of MSDP between Connectors and/or Participants, another option would be to use multi-point peering across a VPLS VLAN with pim snooping to limit the multicast flooding in the backbone VPLS instance.

Thanks.

On Fri, Jun 23, 2017 at 10:36 AM, Michael H Lambert <> wrote:

If you happened to be on the Internet2 connector call on backbone migration a couple of weeks ago, you've probably already heard much of this.  If so, my apologies for the duplication.  At any rate, please bear in mind that I'm not an MPLS expert so some of the technical details presented might not be exactly right.  I'll also throw James Deaton and Bill Owens under the bus as co-conspirators.

There is a significant, but not insurmountable, issue with IPv4 multicast when moving from the current backbone to the MPLS-based backbone.  Because of the way Juniper implements a corner case (meaning it's unlikely to receive attention), each MSDP SA received generates a Type-5 L3VPN BGP announcement.  Under normal circumstances, this generates an acceptable number of announcements.  However, with a full MSDP mesh, an MSDP storm can generate hundreds of thousands of BGP announcements.  Believe it or not, we are still seeing MSDP storms.

One workaround is to filter the BGP announcements.  This does mitigate the effects of the storm, but is not RFC compliant.  Other options that have been discussed include not having the full mesh or limiting the number of Internet2's MSDP peers, effectively requiring connectors to do pairwise MSDP peering.

In order to help Internet2 with resource planning, we'd like to get a better idea of the current multicast landscape.  If you would, please take a moment to respond to the poll at https://doodle.com/poll/zkuvs2vc6dh5dmvr.  Please note that we are concerned only with IPv4 multicast at this time.

The poll will close at 2100 UTC on Friday, 30 June.

Thanks,

Michael

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David Farmer              
Networking & Telecommunication Services
Office of Information Technology
University of Minnesota  
2218 University Ave SE        Phone: 612-626-0815
Minneapolis, MN 55414-3029   Cell: 612-812-9952
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