A concern about draft-acg-mboned-multicast-models recommendations

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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