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

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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.

 
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Pieter Schepens

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Posted 3 weeks ago

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Brian Powers

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EightOhTwoEleven

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I think we are expecting a better answer.
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alösdjfkhoiuyvd32145

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I'd second that, a link to the wikipedia page of apple ios would have been as suficiant ;-)
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FrancisA

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Ironically, many of our Airplay issues went away when we had the AppleTVs connect to a different SSID and VLAN.  This way, it forces the iPad to use direct, peer-to-peer Airplay instead of through our WiFi network.  It also solved the issue of iPads seeing too many AppleTVs as it only detects those in its immediate vicinity (discovery is via bluetooth, I think).

Our environment:
140+ classrooms, each with an AppleTV.  220 APs (R500,R510,R310) on Smartzone.

AppleTV SSID has no password, but uses MAC authentication.  This makes it easier for us to join them on WiFI, versus adding profiles for 802.1x.  We used WPA2 passwords before, but those tended to leak out to students.

We also disabled channels 149 and 153 as these are used by peer-to-peer Airplay.

Hope this helps!

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EightOhTwoEleven

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The downside to this is you're creating another SSID which could impact performance for other SSID since it uses Management, Control frames.
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alösdjfkhoiuyvd32145

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Good point, but for up to 4 or 5 SSIDs the impact is not too big. As I recall it the Airtime Usage with ac SSIDs is about 3% per SSID.

But I don't broadcast the AppleTV SSIDs anyway, since I don't want anyone who shouldnt know to be able to mess with my screensharing SSID - I have had that in an event a couple of years ago and the result was not very funny - at least for the customer... 
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EightOhTwoEleven

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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.

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alösdjfkhoiuyvd32145

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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.
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Brian Powers

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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. 
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alösdjfkhoiuyvd32145

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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 ;-)
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Pieter Schepens

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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.




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alösdjfkhoiuyvd32145

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That's quite a list, thanks for sharing! I must admit though, that with 20+ AppleTVs a lot of the problems you described just seem to be exactly what I would expect in that environment, and I hardly doubt that you will find a more perfect solution than the one you've already figured out.

What I mean is that AppleTVs are home devices for the living room, and as a necessary means of action from Apples point of view they are designed to work exactly in that environment: the living room. Or the bed room. Maybe another one in the childrens room.

But for the professional and high demanding environement you (and I further above)  are describing, I would simply suggest looking for a professional solution that's made for this environment. We can and will figure out a way to work around Apple's home design, but it will only get us so far.

A software product that we are using and which has brought us better results is the AirServer application: https://www.airserver.com/ 

With good server/pc design (positioning, network design and so on) you might find it better suited.

EDIT: I am not working for airserver :-D after reading the post I just had to point that out.
(Edited)
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Pieter Schepens

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Since we use VLAN pooling, the average amount of Apple TV's in one VLAN is ± 5 or 6. 

AirServer as a software solution doesn't suit our setup: we don't want to place an extra pc or Mac in every classroom. The hardware solution looks promising, but is much more expensive than an Apple TV. If it's 100% reliable to use for Airplay in a peer to peer setup, we could consider replacing our Apple TV's gradually over time. 
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alösdjfkhoiuyvd32145

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the VLAN pooling does'nt really change the rest of the environment though (high density, a lot of Wifi, probably higher demand in reliability, so on). I'm still struggeling with the thought that there "always has to be away to make home-devices work" in a not-home environment.

I've come around the argument "but it works at my home, so why doesnt it work with this expensive IT stuff here" way too often, so please excuse the argument - it might be a little subjective.
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FrancisA

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I feel your pain.  We also experienced the same frustrations over the years.  It's easy to blame the network for every slowdown they experience. 
 
We found that some of the dropouts were likely because of hardware and iOS version and not the network.  This is especially true with older units (think AppleTV 3, Mini 1 and 2).   So far, AppleTV on peer-to-peer is working well enough for us.

Yes, the AppleTV is a home product. But until we find a better alternative that's about the same cost, we're stuck with it.  It's still much better than using miracast with Windows / Android devices (we're a BYOD school)


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EightOhTwoEleven

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Did some testing today with one of our Apple TVs. Was on our internal network with my phone, put the Apple TV on another SSID (our guest network). It seemed to use peer-to-peer. One thing I noticed however, is on my phone, doing a speed test I was getting really slow speeds 5Mbps-8Mbps.. and while this is probably sufficient for most traffic, I suppose this could have some implications as well. Once they were on the same WiFi network (non peer-to-peer) I was getting 60Mbps+ on the speed test. Just something to consider.

Seems our method to ethernet all Apple TVs and just use the Wi-Fi for mirroring/internet will still be what we do.
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Pieter Schepens

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Regarding the power settings of the two radios, what would you suggest (large campus, dense network, lots of Apple TV's, peer to peer Airplay):
  • Enable the setting "Automatically adjust AP radio power to optimize coverage when interference is present"? Some people recommend it, but the documentation says: "In general, Ruckus does NOT recommend enabling this feature as it can lead to sub-optimal AP power levels."
  • Adjust the power manually on the AP's by adjusting TX Power (to min or to another low level?)? Only on the 2.4Ghz band, or also on the 5GHz?
  • Or disabling the 2.4Ghz altogether?
May the wisdom of power be with you.