(included [email protected] and also changed subject to something more
appropriate)
As far as I can tell, so far people have told IETF it's their job to
reduce multicast to make IP based protocol "work" on 802.11 media. That's
at least what I have been seeing. Considering the reactions from other
parties, it seems the "multicast sucks on 802.11" is something 802.11
hasn't heard of before.
The only thing IETF can do is to use less multicast, and the obvious way
of solving it is to just replicate into unicast. This seems like a
suboptimal way to work around the problem if there are a lot of nodes.
From what I read below, one way out of this is the IETF making a clear
statement that multicast is an integral part of IP networking, and if a
medium doesn't support delivering multicast frames in a similarily
reliable fashion to unicast, it's not suited to carrying IP based
protocols (or any other protocol that uses L2 broadcast/multicast).
It seems to me that there are a few paths that the IETF could go:
Write an RFC stating requirements on L1/L2 protocols when it comes to
unicast, multicast and broadcast handling of packets. This could include
options for mechanisms that turned multicast/broadcast into unicast that
certain medias could have as requirements. Then IEEE could create a device
profile that would fulfil these requirements, possibly add a
certification, and then try to get market pressure to require devices to
support this profile. The IETF wouldn't change its mind about how
multicast is used in its protocols after this, but just say "this is the
reality, please deal with it when you create L1/L2 that's supposed to
carry IP".
Or the IETF could just say that this seems like a lost cause,
multicast/broadcast doesn't seem to work on some L1/L2, and start working
on techniques that minimizes broadcast/multicast and change all the
protocols to reflect this new reality.
Something in the middle, but anyway changing the requirements on IETF
protocols to avoid using multicast if it can, documenting where it makes
sense and when it doesn't.
Right now what I am seeing is that there are people who are lobbying to do
away with multicast as much as possible because they see that in reality
it's not reliable on the devices they have tested it on.
What are the odds that 802.11 could agree on a device profile for "IP use"
that would include reliable multicast delivery, and one that there is
reasonable belief that this would gain significant market adoption?
On Mon, 10 Aug 2015, Stephens, Adrian P wrote:
Hello Mikael,
" For me, it seems these 802.11 broadcast/multicast ACK functions should be
"mandatory" to implement if the device wants to support IPv4 and IPv6 networks.
How do we achieve this?"
There are two routes to "mandatory". The standard can indicate something is
mandatory if you support
a particular feature.
The second is certification. This is the not-so-simple task of persuading a
sufficient number of WiFi-Alliance members
that it is in their economic interest to support the feature that a
certification program can be created. Even, given a
certification, the market will still decide whether that is relevant or not.
Best Regards,
Adrian P STEPHENS
Tel: +44 (1793) 404825 (office)
Tel: +1 (971) 330 6025 (mobile)
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-----Original Message-----
From: ieee-ietf-coord [mailto:[email protected]] On Behalf Of
Mikael Abrahamsson
Sent: 10 August 2015 08:32
To: Stephens, Adrian P
Cc: Pascal Thubert (pthubert); Pat (Patricia) Thaler; [email protected];
Dan Romascanu ([email protected]); Glenn Parsons; Homenet; Eric Gray
Subject: Re: [ieee-ietf-coord] [homenet] Despair
On Mon, 10 Aug 2015, Stephens, Adrian P wrote:
The question in my mind is whether this discussion thread is uncovering any new
requirements for the 802.11 standard.
Thanks for the summary, it seems correct.
It might not need new 802.11 standards, but we still have an operational
problem in that it seems some of these standards are not universally
implemented by 802.11 based device vendors.
IETF standards generally assume that multicast and unicast are delivered with a
similar level of packetloss (which is low).
Not all 802.11 implementations have the multicast ACK mechanism implemented,
thus it would seem that multicast will be less likely to get delivered to the
recipient over these 802.11 implementations.
For me, it seems these 802.11 broadcast/multicast ACK functions should be
"mandatory" to implement if the device wants to support IPv4 and IPv6 networks.
How do we achieve this?
--
Mikael Abrahamsson email: [email protected]
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Mikael Abrahamsson email: [email protected]
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