All things related to multicast

[Leonard Giuliano <>]

FWIW, deprecating interdomain IPv4 ASM is something that has been 
suggested at IETF in the MBONED WG for quite some time and there has been 
recent activity on a draft to codify this proposal.

And, personally, I would go even further and suggest why not do the same 
with v6?  While Embedded RP avoids many of the horrors of MSDP, if SSM is 
sufficient for v4 it should also suffice for v6.  Network-based source 
discovery accounts for the vast majority of complexity in mcast 
deployments- both for v4 and v6.  


Thanks,
Lenny

On Fri, 23 Jun 2017, David Farmer wrote:

| 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
| 
| 
| 
| 
| --
| ===============================================
| David Farmer               
Email:
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