Re: [MBONED] A concern about draft-acg-mboned-multicast-models recommendations

Hi Jim!

I think we're converging towards deprecating ASM for *inter-domain* 
use, and what we say about intra-domain models is a bit in flux.  

I think the latest is at the bottom of Tim's most recent message:
https://www.ietf.org/mail-archive/web/mboned/current/msg02543.html

glad to have you here!

Dale

Thus spake James A. (Jim) Stevens (james.a.stevens@rockwellcollins.com) on Tue, Feb 27, 2018 at 04:29:00PM -0600:
> Hi, I’ve only recently joined MBONED, so this email may be rehashing old
> discussions. (If so, please just point me to the prior discussions.)
> 
> With respect to multicast service models, I support customers who field
> hundreds to thousands of nodes where each node is a member of multiple
> (typically five to ten) multicast groups where most of the groups have
> dozens to hundreds of members that partially overlap in membership between
> the groups.  All of the members of the multicast groups are both multicast
> sources and receivers.  The nodes are spread out over multiple IP links
> (typically wireless).  The multicast groups are within a single IP routing
> domain that can contain dozens to hundred of IP links and subnets.  The IP
> links are typically other than standard WiFi or cellular IP links and have
> limited throughput capacity – ranging from tens of kilobits/sec to a few
> megabits/sec – so a key concern is to keep overhead down.
> 
> For this multicast scenario with many dynamic bidirectional sources and
> receivers, we use ASM rather than SSM model to reduce management overhead
> and simplify source discovery by not having to track which nodes have
> joined which groups in order to do an SSM join to all the members of the
> group.
> 
> The draft-acg-mboned-multicast-models-02 recommends “the use of SSM for all
> multicast scenarios.” For this multicast scenario, I don’t see how SSM
> efficiently satisfies this many multiple sources and receivers – especially
> since the multicast members are dynamically joining and leaving.
> 
> Thus, I argue that SSM is not always the best multicast model and there
> shouldn’t be a blanket recommendation to use SSM for all possible multicast
> applications. In addition, I recommend section 7.6 address the fact that
> SSM is not as efficient as ASM for the case of many dynamic bidirectional
> sources and receivers.
> 
> Or, am I overlooking something on how to use SSM to address scenarios with
> many dynamic bidirectional sources and receivers?
> 
> Thanks,
> 
> Jim Stevens

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