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LAWN mDNS/Bonjour (Apple AirPlay, Mirroring, etc) Pilot


We have enabled mDNS/Bonjour on all LAWN networks (eduroam, GTother, and Wired LAWN) to allow experimentation with Apple AirPlay, Apple AirPlay Mirroring, and iTunes Music Sharing). Note that the AppleTV must either be wired or on GTother since it does not support WPA2-Enterprise. We recommend getting Device Registration for AppleTV's on GTother.


THIS IS A PILOT, and as such, expect issues with the experience. On the network we may encounter issues which require on the fly changes that could render features inoperable. The features themselves might not scale to our network, or generally be less than what you expect on your home network. As such, YOU SHOULD NOT RELY ON THIS as your only means of doing presentations or demonstrations, and we don't recommend making significant investments based on the availability of these features. SUPPORT FOR THIS PILOT IS BEST EFFORT, both from OIT and from Apple (Apple does not officially support enterprise use of Bonjour services). Beyond this please note that there are steps below that users need to take in order to protect their data, limit the opportunity for others to disrupt their work, and improve the scalability of the service. 

Enabled Services (What should work)

  • AirPlay - Allows users to play content on iOS or OSX devices on wireless devices (Apple TV, or speakers), includes Mirroring, and Dual Screen content. http://www.apple.com/airplay/
  • AirTunes - Allows users to stream to iOS devices or AirPort Expresses over a wireless network from iTunes. http://www.apple.com/itunes/inside-itunes/2010/02/itunes-and-airtunes.html
  • iTunes Sharing - Like HomeSharing, but does not allow users to copy from or write to library. Allows users to use shared media libraries across the network. Users should password/passcode protect their libraries!

IMPORTANT NOTE: At this time, we do not allow any other Bonjour services such as Home Sharing, Apple Keynote Remote, Mobile Device sync, etc. The above list are the only services we allow on the LAWN at this time. We are working toward allowing additional services. This list may change so please check this page periodically.

Results: What works and what does not work

Here is a start to some of what we have observed:

  • AirPlay to AppleTV: the Apple TV needs to be on GTother or wired LAWN, but the other device can be on any LAWN network. We recommend LAWN Device Registration for easier use of AppleTV on the LAWN.
  • AirPlay to non AppleTV: devices can be on any LAWN network. For those interested in AirPlay from an iOS device to a laptop (with VGA output for example), check out AirServer

Best Practices

  • Name your AirPlay devices appropriately. Use a name that you can easily identify. Refrain from using "questionable" names. Do not try to push yourself to the top or bottom of the list with opportunistic naming of your device (this doesn't usually work!).
  • Password protect any devices and services you associate with a wireless network. This includes putting a pass code on the AppleTV AirPlay feature (Settings->AirPlay), and disabling sharing or requiring a password in iTunes (iTunes->Preferences->Sharing). Be sure to change the password after you have shared it with others.
  • Turn AirPlay off when not in use. If you only require the internet based features of the AppleTV, it need not be on LAWN at all, another wired network will suffice.
  • Visit this page (http://lawn.gatech.edu/services/Bonjour/) for up to date information based on things we learn.

LAWN Refresher

LAWN is made up of multiple networks which are accessed through the eduroam and GTother wireless SSIDs as well as wired LAWN ports. When a user authenticates to eduroam (in this case the iOS device and laptops), they are placed on a network based on their user id. This means that by default all of your eduroam devices are placed on the same network, similar to what happens on your home network...only you are sharing that network with 4000 of your closest friends! Note that this works throughout the campus and is not location dependant, allowing devices and applications to stay connected as you are mobile. At this point in time all GTother users are placed on a separate network regardless of their username (this will change with the upcoming replacement of GTother). By default, any device on LAWN can communicate (unicast) with any other device on LAWN regardless of which of these networks you are connected.

Network Changes Made

There are three primary changes that have been made to LAWN networks. First, we enabled multicast routing on each LAWN network so that hosts on the same LAWN network could communicate with one another. Second, we allowed mDNS multicast packets to propigate between all LAWN networks. Third, we are filtering mDNS traffic based on service type and are limiting support for a limited set of Bonjour service types. This is primarily done to minimize negative effects of Bonjour on an large scale enterprise network.

The net result of these changes is that applications that use Bonjour now generally work between devices on LAWN; however some features of these applications have issues working across LAWN networks.

In some cases your target devices or libraries are discovered, selectable, and you appear to be able to connect, but no content appears. While the AppleTV should not require Internet access for this to work, in some cases authenticating the AppleTV on LAWN resolves the issue https://auth.lawn.gatech.edu/index.php. NOTE: To authenticate your AppleTV to LAWN you need to know the MAC address of your AppleTV, which is located in the Settings->General->About and is called "WiFi Address" when GTother, and "Ethernet Address" when plugged into a wired LAWN port. Remember that the device needs to be authenticatated each time it is connected to GTother or a LAWN port.

You can request LAWN Device Registration to have your AppleTV automatically register itself on the network if your device is connecting to GTother or a wired LAWN port.

Please contribute to the forums on this page to communicate feedback based on your experiences, including working and non-working configurations/features. Send other feedback to lawn-feedback@lists.gatech.edu

Please note that the forums are not meant as a replacement for the official OIT help system ServiceDesk (which can be reached via email, support@oit.gatech.edu, or via the phone at 404-894-7173).

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Forum Posts

July 18, 2012, 10:22 am

On Mac OSX we have seen a few situations where the system.log is presenting the following errors repeatedly.

“Jun 26 19:26:12 [hostname] mDNSResponder[12]: Client application bug: DNSServiceResolve(xx:xx:xx:xx:xx:xx@XXXX::XXXX:XXXX:XXXX:XXXX._apple-mobdev._tc p.local.) active for over two minutes. This places considerable burden on the network.”

In our efforts to mitigate this issue we have found success with the following steps.
1. Use Spotlight (upper right hand corner) to search for “Activity Monitor.” Select the icon with “Applications” to the left of it and start the Activity Monitor utility.
2) Once "Activity Monitor" has started, select "All Processes" from the pull down menu.
3) Highlight "mDNSResponder" by clicking on it.
4) Click the icon shaped like a stop sign labeled "Quit Process"
5) A dialog box will come up, select "Force Quit" (don't worry, the process will restart, you may need to enter your administrator password at this point)
After this process the errors should stop.

September 10, 2015, 12:12 pm

September 10, 2015, 12:12 pm

Since there are quite a few Raspberry Pi and similar ubicomp and IoT projects here, it would be great if we could use mDNS to connect to them via .local domains.


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This page last modified: Aug 22, 2018 at 03:16 PM EDT
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