Large campus network: best practices for Airplay (+ issues with lots of Apple TV's)

[pieter_schepens]

We have a large campus network: ZoneDirector ZD1200, ± 50 AP's R500 and R510, ± 100 Apple TV's, lots of iPads (1:1 and shared iPads). The Apple TV's and iPads are on the same SSID, but in small VLAN's/subnets. The backbone of our network has high performance. WiFi speed and reliability are perfect.
We use AirPlay mirroring to the Apple TV's to cast the screen of the teachers iPads to the projector or TV screen. We don't use Bonjour Gateway. From time to time, we experience drop outs or lag in the Airplay streaming. 

We'd like to know, when configuring a WiFi network for AirPlay with lots of Apple TV's:

• What are the best WLAN settings?
• What are the best settings for things like self healing, background scanning, load balancing, etc...?
• What are the best settings for the AP's?
• Any other best practices to make AirPlay reliable?

Any help or advice is greatly appreciated.

 

[eightohtwoeleve]

Actually with 4 to 5 SSIDS, that's actually a fairly sizable performance hit you take. Especially if one AP sees another on the same channel. If that occurs it exponentially gets worse. See here - http://www.revolutionwifi.net/revolutionwifi/p/ssid-overhead-calculator.html

Also, just because you don't broadcast the SSID, doesn't mean that frames aren't using up airtime.

[fghzuio]

that's not entirely true. in the list provided at revolutionwifi you can select the standard (a/b/g) you want to work with and the airtime the SSID broadcasting(management is using is considerably less in anything else than in b (which is used as picture on the blog link provided). And since there's no mentioning of n or ac it safe to assume that it's a little outdated nowadays.

But of yourse you are right, less SSIDs is always a better performance. It's just not as critical with four to five than with four so ten.

[brian_powers]

Remember, beacons for SSIDs always come out at legacy data rates (1-54 depending on what rate your lowest mandatory rate is set to).  So 802.11n/ac/ax are irrelevant to beacon overhead. 

[fghzuio]

It's a very interesting topic to be honest. I'm using AppleTVs in live event environments of different sorts, and my approach is always:

• connect AppleTVs via ethernet
• disable all bluetooth connections or similiar funktions, that might unconrtollably force the traffic over a path that I do not want
• connect the iPads in a special Wifi&VLAN only for the screensharing purpose, that's directly connected to the AppleTVs ethernet ports
• if possible make sure that there's a line of sight between ipad and Wifi AP
• make sure the ipad is connected to that specific AP by only using the SSID on this single specific wifi AP
• make sure that it actually CAN connect to that AP (amount of clients per radio/SSID should not be blocked by too many other devices in other SSIDs
• make sure there is no auto channel and no auto signal strength - channel hopping will break connectivity for a very short amount of time, changes in signal strength only adjust too slowly
• make sure the wifi channel is not too heavily crowded (I always use 5GHz only for that AppleTV SSID)

Still looking for the technical specifications of what I have just said, but it's my experience to actually have it working when it must.

Of course I could imagine that my approach is not really applicable to school/campus scenarios because of the high amount of dedication in single hardware APs. But then again I dont work at a school and couldnt really judge 😉

[pieter_schepens]

Thanks everyone for your advice. Some comments from our experience:

As we have lots of clients and ATV's, everything is segmented in different VLAN's. We tried different approaches over the course of time: all the ATV's in one seperate subnet/VLAN (apart from the clients), with and without Bonjour gateway; the Apple TV's in several separate VLAN's, etc.

Some of our experiences:

• As long as we had very few Apple TV's and few clients, there was no problem.
  
• More than ± 20 Apple TV's in one subnet/VLAN, together with the clients: drop outs and lag.
• More than ± 20 Apple TV's in one separate subnet/VLAN, apart from the clients, with Bonjour gateway: drop outs and lag.
• Apple TV's in several separate subnet/VLAN, apart from the clients, with Bonjour gateway: even more drop outs and lag (Bonjour gateway rules miltiply).
• Apple TV's and clients together in one SSID, but segmented into several VLAN's/subnets, without Bonjour gateway (using peer to peer connections): significantly less drop outs and lag than in the setup with Bonjour Gateway, but still too many problems to call this a satisfying setup.
• For the separation into VLAN's, we tried two approaches: first with VLAN override per AP group, later with VLAN pooling; VLAN pooling is much easier to setup, so that's what we chose for our current setup (although you're almost certain the client and the Apple TV are not in the same VLAN).

Other things we did, based on the advice or experience from others:

• Because we're using peer to peer connections without Bonjour gateway: connect the Apple TV's wirelessly, not on ethernet.
• Channels: limit the 2.4GHz band to channels 1, 4, 7 and 11; disable channels 149 and 153 on the 5GHz band.
• Radios: disable the 2.4GHz radio on every other AP.
• No peer to peer blocking/client isolation.
• Don't drop multicast packets.
• Na rate limiting.
• Use OFDM-only.
• Enable 802.1d.
• Disable directed multicast.
• Disable IGMP snooping.
• Load balancing: don't use client load balancing or band balancing.
• Self healing: Automatically adjust AP radio power to optimize coverage when interference is present + use Background Scanning.

The situation now is much better than it used to be, be still not satisfying enough: we keep experiecing drop outs from time to time.