It's been a year now, Things have progressed. We have been and are still implementing an AirPlay savvy environment for our faculty at our university. Campus has been going through a series of security audits and has had to proceed with caution with this.
As far as what ports are used, refer to this http://support.apple.com/kb/HT2463
Here is what we have done.
Net admin is now providing a wifi network that is used only for wireless presentations. This is a Cisco network with Aruba access points. This presentation network is unsecured for lower latency and it allows all mDNS traffic (bonjour, AirPlay, etc). This network is closed, hidden and part of the existing campus network architecture. Access to the internet fom this network can only be had by authenticated users (faculty/staff). Currently all devices and libraries have to be on this one network. The Apple TVs had to be granted firewall pinholes to the internet for access to apple's time server. If the apple tvs need access to any online resources then port 80 must also be opened. I will note that leaving port 80 closed eliminates all the apple store movie/music promotions and leaves only two selectible options, Computers(homesare libraries) and Settings. This certainly keeps classroom distraction to a minimum but disables YouTube and other useful class resources. Serving up our .local in house content to this network is a mac mini server hosting 5 itunes libraries, 4 of which have homeshare enabled to match all the Dept. appleTVs. 1 library has its "Automatically Add to iTunes" folder shared as a faculty sharepoint in order to provide a way for teachers to populate this library with class specific material. Using the Remote app, faculty can create and manage playlists without needing to sit down at specific computer. The only major annoyance of using the remote app is that when launched it attempts to touch the internet. This in turn trigers the authentication for internet access login so a user has to pause ounce in a while to authenticate. Apple has not had a response to this as of yet.
Here is what we still want to do:
We need to look into localizing all dept resources into one zone. Preferably one that can bridge the wired vlan and this wifi presentation networks. The reasons for this are: A) keep the list of resources specific to its dept. B) Allowing the media computers to stream directly to the appleTVs via wired network in order to increase media load times and reduce impact on campus wifi bandwidth. This bridging of networks is where the security and management issue for ITS.
As it turns out, there are companies tailoring products to address this. Auba and Aerohive networks are offering what is being called an mDNS gateway function. I hope to see a working test soon.
This is a far cry from where we started but its complexity has added many benefits. BUT, in the case of straight in-classroom airplay presentation I would stick with adhoc as Chenks suggests. Its far less complicated and getting permissions are minimal depending on who you ask 😉
On a side note, I've also tinked with a MAC and PC app (AirServer) that turns most any computer with a projector into an AirPlay receiver. An in-classroom computer wired to the network and using a projector as an extended desktop rocks quite nicely providing in-classroom adhoc wifi for AirPlay. Not sure how the school is gonna feel about this test, but since I didn't ask, permission was not denied. 🙂
Hope that helps.