On Wed, 12 Aug 2015, Henning Rogge wrote:
0.1% multicast packet loss is unrealistic.
I found this interesting document:
https://hal.archives-ouvertes.fr/tel-00919403/document
In 2.4 there is a lot of text about different ways of making multicast
(more) reliable.
From what I can see, the control plane (for instance RA/ND/ARP etc) (this
does not include video transmission) of IP based protocols have the
following requirements for its broadcast/multicast packets (from now on I
will only say multicast):
Multicast packets should be delivered with less than 1% packet loss
Multicast packets should be delivered within 200-500ms (for instance DAD
requires answer within 1s)
This would indicate to me that 802.11 could do the following to achieve a
compromise between power, packet loss etc:
If the multicast packet is to be sent to X receivers or fewer, turn them
into L2 unicast, and send them individually (tradeoff between sending X
packets and using a lower rate multicast). X could be 2-4 or something?
Send IP control plane multicast packets at an interval, for instance
250ms, so stations can sleep in between.
Send multiple packets at the above interval if there are multiple ones
queued up, use BNAK for retransmits, potentially turning
to-be-retransmitted multicast packets into unicast (re)transmits to send
to individual stations that didn't receive the multicasted packet(s).
(I don't know if this is already being done) Stations should send IP
multicast packets to the AP in L2 unicast so the AP can then send it as
multicast using above mechanism, including queuing it for multiple
delivery.
Thoughts?
--
Mikael Abrahamsson email: [email protected]
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