Re: [Mcast-wifi] Multicast and Wireless (fwd)

Mikael Abrahamsson <swmike@swm.pp.se> Wed, 19 July 2017 16:51 UTC

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Date: Wed, 19 Jul 2017 18:50:58 +0200 (CEST)
From: Mikael Abrahamsson <swmike@swm.pp.se>
To: mcast-wifi@ietf.org
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Subject: Re: [Mcast-wifi] Multicast and Wireless (fwd)
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Hi,

Below is an email I wrote to the approximately 10 people who were 
"gathered" to discuss how to proceed with the wifi-multicast "problem".

In the meeting, there were lots of discussions, some regarding catching up 
with what had been discussed before, but the last 30 minutes (in my 
opinion) were productive. There were solutions proposed, and I'd like to 
get shared here in writing. Please invite more interested people and make 
them aware of this list, and let's do the discussions here. I will do some 
announcements on other lists to bring awareness to this list.

One proposal was that we could make sure 
http://www.ieee802.org/1/pages/802.1ak.html was available in end systems, 
and this could be adapted by 802.11 as one way to help the APs handle 
multicast load by letting them more easily identify how to turn multicast 
packets into unicast packets.

Another proposal was to just do less multicast by redesigning IETF 
protocols and how they behave.

WHen we're saying multicast here, we're talking L1/L2 multicast, ie 
sending multicast/broadcast packets over wifi between devices connected to 
the same L2 domain. This can be IPv6 ND/RA packets, but also service 
discover such as Bonjour packets.

I would like to have the people who proposed the solutions to elaborate on 
what their thinking was.

----

Hi,

there is nothing concrete being proposed as far as I know. Alia indicated to me 
she was still looking for a problem statement.

The problem statement I was involved in writing 2 years ago:

https://www.iab.org/wp-content/IAB-uploads/2013/01/multicast-problem-statement.pptx

https://www.ietf.org/mail-archive/web/int-area/current/msg04903.html

https://www.ietf.org/proceedings/94/slides/slides-94-intarea-1.pdf
At the end there are multiple links to problem statements etc.

>From what I can tell, there is a problem. It's unclear what should be done 
about it, if this is a IEEE problem to make sure wifi works well with 
multicast, or if IETF should adapt its protocols to handle the way IEEE does 
multicast over 802.11 without the special mechanisms for improved multicast 
reliability that isn't widely implemented in currently shipping devices.

So I guess this is what we're supposed to consider.