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

Hi Jim,

Indeed. I argued the same point, but not necessarily for the same reason as you.

I think the resolution might be to insist on SSM more for the inter-domain model than for intra-domain. Intra-domain, like in your case and mine, there are times when ASM is way simpler to implement. (I used the multicast-emulation-over-ATM, which resembles SSM conceptually, to shame the mboned wg into not demonizing ASM entirely!)

Bert


From: MBONED [mailto:[email protected]] On Behalf Of James A. (Jim) Stevens
Sent: Tuesday, February 27, 2018 17:29
To: [email protected]
Subject: [MBONED] 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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