Technology Blog

Apple TV Peer-to-Peer using WiFi channels 6 and 149

by ‎01-14-2015 11:12 AM - edited ‎01-15-2015 06:32 PM

Introduced in iOS 7.1, peer-to-peer AirPlay uses BTLE for a discovery process. No longer is a network infrastructure required for discovery and even direct communication. 

 

From Apple:

 

iOS 8 supports the ability to stream content from an iOS device to Apple TV even if the devices are on different networks or there’s no network available. The iOS device uses Bluetooth Low Energy (BTLE) to begin the discovery process of available Apple TV devices and then establishes a connection directly to Apple TV using Wi-Fi.

 

 

In iOS 8, peer-to-peer AirPlay lets a user use AirPlay directly from a supported iOS device or Mac to an Apple TV without first connecting to the infrastructure network. Peer-to-peer AirPlay eliminates the need to join the right network or disclose Wi-Fi passwords, avoids reachability issues in complex network environments, and provides a direct path from the AirPlay sender to AirPlay receiver to optimize performance. Peer-to-peer AirPlay is enabled by default in iOS 8 and Mac OS X Yosemite v/10.10, and doesn’t require any user configuration.

 

 

This is where it gets interesting

 

Peer-to-Peer discovery is initiated using Bluetooth Low Energy (BTLE) when a user selects AirPlay on an iOS 8 or OS X Yosemite v/10.10 device. This causes the device and the Apple TV to visit Wi-Fi channel 149 in the 5 GHz band and Wi-Fi channel 6 in the 2.4 GHz band, where the discovery process continues. Once the user selects an Apple TV and AirPlay starts, the Wi-Fi radios timeshare between channel 149 and whichever infrastructure channel each device is currently using. If possible, the AirPlay sender roams to the same infrastructure channel the Apple TV is using. If neither device is currently using an infrastructure network, the devices will utilize Wi-Fi channel 149 only for AirPlay. Peer-to-peer mirroring adheres to 802.11 standards, sharing Wi-Fi bandwidth with other Wi-Fi devices.

 

Apple’s play on deployment 

 

When you deploy Apple TVs on a large enterprise Wi-Fi network, consider the following guidelines:

 

Connect Apple TVs to Ethernet whenever possible

Don’t use Wi-Fi Channel 149 or 153 for your infrastructure network

Don’t place or mount the Apple TV behind objects that could disrupt the Bluetooth Low Energy and Wi-Fi signals

 

 

 

http://help.apple.com/deployment/ios/#/apd8fc751f59

 

 

Wirelesssguru’s take:

 

While I don't consider Apple TV as an enterprise grade solution. One advantage of Apple TV in the enterprise is wireless screen sharing. It’s an inexpensive solution and easy to deploy, once all the network gymnastics are worked out with bonjour. This BTLE feature can allow guest or contractors screen sharing without compromising wireless network security. 

 

Apple points out WiFi channels are used as part of the discovery and adhoc connection. As a WiFi engineer, when deploying these solutions, we need to be aware and address any channel concerns. A study of channel duty and behavior should be validated before deployment. Im glad Apple is leveraging the 5 GHz spectrum for adhoc streaming. But Im also concerned about the behavior in the comment “ Once the user selects an Apple TV and AirPlay starts, the Wi-Fi radios timeshare between channel 149 and whichever infrastructure channel each device is currently using”. 

 

What do you think ? Share your comments ..

 

Enjoy! 

 

 

Comments
Guru Elite Guru Elite

Great write-up!

 

I definitely see Chromecast as a more viable solution than AppleTV because of what you explained above and also that Chromecast works on all platforms, whereas AppleTV is locked to Apple products (unless you purchase clunky software that attempts to replicate the service).

MVP MVP

I am seeing more enterprise customers (financial) begin to go paperless and their product of choice is iPads with Apple TVs.

It has become quite a pain to get it working and this write up is extremely interesting!! Thanks for sharing.

 

I do agree with Tim on the use of Chromecast vs ATVs. Wider selection of platforms.

I have to agree we are seeing it as well. Also Thanks for supporting the Kudos system! Much appreicated ! 

eggplantpit

Aren't there channel spreading rules in 5GHz by FCC?  Maybe that's DFS bands only.

Moderator

Other odd AppleTv behaviour can be seen on channels other than 149/153, here is a capture I made of an ATV that was powered off in a room with no one in it, blasting out on channel 64.

 

When a macbook entered the room and tried to Airplay to this ATV, it start using channel 64

 

seems to cause the APs some distress too given these are malformed action frames.

 

atv_64.png

 

 

hypnot0ad

@cappalli check out airparrot by airsquirells. Its super smooth and not clunky at all and definatley bridges the gap where Enterprise mandates the ease of apple devices, but IT requires interoperability and functionality

Guru Elite Guru Elite
Paying for commercial software to put on clients isnt always feasible either. 

Chromecast = cross platform, no client, $35 = win, win. 
MVP MVP

what i wonder is how this affects the ClearPass airgroup enforcement functionality? still not 100% sure that if bluetooth is turned off then this method wont work?

 

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