Behavior over preference of APs and bands?

[Rubin Abdi]

My environment:
Thinkpad X220 - Intel Centrino Advanced-N 6205
Debian Sid amd64 KDE
firmware-iwlwifi	0.41
wpasupplicant		1.1-1
network-manager		0.9.8.10-3
plasma-desktop		4:4.11.8-1

There are two behaviors in the way my machine connects to wifi that I'm
trying to wrap my brain around. The first I think has a fairly straight
forward answer.

If I wake up my machine from sleep, and there are multiple SSIDs with
range that I've already connected to and remember through Network
Manager, which is connected to first? Network Manager doesn't seem to
have any sort of network priority function currently (unlike OSX or
Android 4.x). My guess is that Network Manager will check to see if any
networks it remembers are within range, then connect to the one with the
least amount of noise.

The more brain itching question I have is how does it deal with this
connection preference when there are multiple APs on different bands
broadcasting under the same SSID? I've thus far testing out my
environment against Ubiquiti Unifi Pros and last generation Airport
Extremes, both of which have dual 2.4GHz and 5GHz radios, and typically
default to a config of using the same SSID for both radios. Neither to
my knowledge employ any sort of band steering (though it sounds like
that's an option Ubiquiti wants to add soon).

With both setups my laptop by default connects to the 2.4GHz network the
majority of the time, even if I'm sitting with line of sight from the
back of my laptop to the AP in the same room. Generally signal strength
for 2.4GHz is higher than 5GHz and I totally get that in most cases when
you're not in a part of the world saturated with technologically advance
humans, 2.4GHz is generally better for in home use. Occasionally it'll
roam over to one of the 5GHz networks, and when I go check out signal
strength 2.4GHz still has somewhere around 10% higher signal as reported
through NM.

Is any of this behavior documented everywhere? Is there any way to tweak
this? Ideally I would set something up like go with the 5GHz network
first unless 2.4 has a 20% lead in strength.

Thanks!

-- 
Rubin
rubin at starset.net

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