Re: [Bloat] wifi AP switching time

[David Collier-Brown <davec-b@rogers.com>]

On Jan 1, 2013 6:50 PM, "Michael Richardson" <mcr@sandelman.ca> wrote:
>> A comment was made a month ago or so about how long it takes wifi APs
>> to switch from transmitting (unicast) to one station to another.  That
>> there was quite a large latency here, and that this was one reason that
>> the AP designers wanted large buffers to accmulate, so that the
>> switching time could be amortized over a larger number of packets.

Pedro Tumusok <pedro.tumusok@gmail.com> replied
> I might be way of here, but to me this sounds like a-mpdu which is used to
> aggregate frames to get higher throughput. Thats in the specification, its
> in 802.11ac and I believe that it go introduced with 802.11n.
> 
> It is there to mitigate the overhead of aquiring the channel.

And that in turn sounds like a place where codel may be needed to ensure
the buffer drains down to nothing in the general case. Alternatively, a
simpler approach might be to buffer only when actively trying a acquire
a channel.

I wonder if there are other only-for-one-reason buffers lying around in
the communication path (;-))

--dave
-- 
David Collier-Brown,         | Always do right. This will gratify
System Programmer and Author | some people and astonish the rest
davecb@spamcop.net           |                      -- Mark Twain
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