Sonos "AP" in INFRA mode

  • 16 January 2018
  • 9 replies
  • 296 views

I run our Sonos speakers in infra mode, connected to our Ubiquiti Wi-Fi network, which covers the whole house really well. Using Ubiquiti airTime I see what looks like a WLAN access point that's utilizing almost 10% of RF airtime when Sonos is playing. The MAC address belongs to the Sonos speaker which is currently serving as the controller. I would expect to see this if one of my speakers is plugged into Ethernet and Sonos is using its SonosNet mesh. My question is: why is this happening in infra mode?

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9 replies

By "the Sonos speaker which is currently serving as the controller" I assume you're referring to the group coordinator. Grouped or bonded players will still talk to one another directly if they can, even in Station/Infra mode.
Ok. These are grouped. How do they choose the Wi-Fi channel to use for that communication?

Would be so great if future speaker models could support 5 GHz too.
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I have no idea what INFRA mode means

When in Boost mode (ie if you have one Sonos device wired to the router) then SonosNet will be used, a channel will be selected by default - I have no idea if Sonos default selects 1 (say) or if it randomly selects. I assume it defaults to 1. The user can change this in the relevant settings section.

Sonos speakers already use 5 GHz when they are configured as surrounds with a Playbar/Playbase
Ok. These are grouped. How do they choose the Wi-Fi channel to use for that communication?
They use the same physical channel as the primary WiFi. The radios are not frequency-agile.

This means that where there are multiple APs, direct connection between grouped Sonos nodes attached to different APs can only occur if the APs share a common channel.

If you're interested, go to /proc/ath_rincon/station for the relevant nodes in http://x.x.x.x:1400/support/review. Although arcane, there's some interesting data in there. You can see the traffic directly from the AP under RX Stats. A grouped node receiving directly from the group coordinator will show relatively few packets from the AP itself.

Would be so great if future speaker models could support 5 GHz too.

In theory, the dual-band models could do this. Sonos choose not to implement it (other than for PLAYBAR/BASE satellites), presumably on the grounds of range and reliability.
I have no idea what INFRA mode means
WiFi mode, Standard Setup.
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Interesting... I never realized that Sonos speakers continue to communicate directly with each other wireless, even if they're on a WiFi network... I assumed it would all be over the WiFi network. I suppose that's how they maintain low[er] latency for the purpose of grouping... of course, if they're not close enough for direct communication, I assume everything DOES then go over the WiFi network?

So there's still a "SonosNet" behind-the-scenes, even when WiFi is being used... it's just not the primary means of communication.
For a SonosNet system, look in /status/showstp (or /usr/sbin/brctl showstp br0 from /support/review). Wireless tunnels show (remote STP state = xxx, direct = N). N=3 means a direct connection is possible, with the remote node wireless; N=1 is the same except the remote node is wired. N=0 means direct isn't possible.

On a Station/Infra system, STP is not active. However look in /proc/ath_rincon/status and the peer-to-peer wireless tunnels are up, albeit 'blocked'.

Direct connection will be used if possible, in both cases. If direct signal strengths are too low, or in the Station/Infra case the nodes are attached to APs with different channels, then the usual tree is followed: STP or WiFi.

FYI: https://www.google.com/patents/US9521074
Thanks Ratty, very helpful. I'll have a look at the patent for more details but I have one remaining question please: If all of the speakers in a group are associated only with APs which are all using the same channel, will there still be the need to create this separate common channel that I'm seeing in airTime?
Not being a Ubiquiti user I don't quite understand the reference. The group coordinator will, where it can, transmit directly peer-to-peer to other members of the group. Like any participant in a shared medium (the channel) the coordinator therefore accounts for a fraction of its utilisation. There is no 'separate' in this context.