On 12/01/2021 18:04, Chris Green wrote:
> When I copy from laptop to desktop (both quite fast machines with fast
> disks) I get something quite a bit over 100MB/s on wired Gigabit
> connections.  So the overhead isn't that great given that the
> theoretical maximum would be 1000/8 which is 125MB/s.  So on a 300Mb/s
> wireless link between the same two machines one would, sort of, expect
> something a bit more than 30MB/s whereas in reality one gets about
> half of that.

in general I have found that on a good link, speeds of a little over
1/10th Mbps rate to be obtained at the byte level, So overheads  is not
that heavy a penalty.

Probably ~10%
That's on a *full duplex* link. Broadband is full duplex. Ethernet of
the cat 5 sort is full duplex.

Wifi is NOT full duplex.

That means that any ACK packets going back share bandwidth with the
forward data stream, In a fairly nasty 'wait till the stream packet size
is exceeded, then send an ack oh dear collisions/backoffs/try again...'
sort of way.

When my Pi zero link was going titsup before I slapped in an access
point 5 feet away, although it *said* it was connected at 5Mbps, it
couldn't support a 128kbps stream of audio.
My so called 72Mbps links couldn't handle HD TV, which is around 5Mbps I
think, reliably.

I now have an Ethernet cable to where the laptop lives






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