Found the following on AVSforum :
http://www.avsforum.com/avs-vb/showthread.php?p=20422004#post20422004
8. Networking
a. Airplay: The Airplay feature (audio only) is offered on the networking models 1912, 2112CI, 2312CI, and 3312CI. It allows you to stream your iTunes songs wirelessly from your laptop, iPhone 3GS or iPhone 4 (will not work with iPhone 3G), or iPad to one of the above models when both are connected to your home network. This feature can also be replicated on non-networking models by using an Apple TV (audio and video) or Airport Express connected to the AVR. There is however, a limitation when using the on board Airplay feature in that although you can play Airplay audio to either the main zone or Zone 2, when playing to Zone 2, you cannot play another source in the main zone (unlike when you play another source to Zone 2). This same limitation exists with the firmware upgrade to the 3311CI/991 and 4311CI. When using the Apple TV or Airport Express, this limitation does not exist. Also note that Apple currently has only licensed AVR mfr's to use Airplay in "audio" only mode. Although rumors are that Apple may soon license AVR mfr's to stream video, AFAIK Denon is not going to support Airplay video streaming in the XX12 models. For the 1712, 1912, 2112CI, and 2312CI you would also need to buy an optical to RCA analog converter (DAC) similar to this one to be able to pass the ATV's audio to Zone 2.
A "wired" connection from the AVR to the router/modem is preferred to reduce connection issues and reduce audio dropouts due to buffering. If you don't want a networking model, adding an Apple TV will give you Airplay, although there are noted issues with the ATV having audio droputs regardless of the brand of AVR connection. Some have noted that turning off bluetooth and closing background applications on your iphone, ipad, etc. will reduce/eliminate the Airplay audio dropouts. Also, if having connectivity issues, try unplugging the AVR for a few minutes and then power on again.
Notes:
(1) When using Airplay from a PC or laptop, the volume for your surround system is controlled by the PC/laptop volume so be sure it's turned down before starting to stream the audio.
(2) If you want to turn the AVR ON to use Airplay, make sure NETWORK STANDBY is set to ON, and download one of the REMOTE apps listed in para 8f below,
b. Connecting to a home network: None of these XX12 models are "wireless" or include the capability of being wireless by adding a dongle. You must either connect the network capable AVR directly to a router/modem with an ethernet cable (recommended) or connect the AVR to a wireless bridge like this one or this one or this one or use Powerline adapters that plug into nearby outlets that can then connect to your wireless router/modem. Using Powerline adapters effectively turns your house wiring into a "wired" network. If you don't plan on using the network capability for other than firmware updates, 100' Cat 5 ethernet cables are fairly inexpensive and available from forum sponsor Monoprice. You can also purchase 1000' cable if longer length is required. If you are experiencing intermittent audio dropouts while using the network streaming feature, consider connecting the AVR directly to the router rather than a wireless connection or consider upgrading to a newer, better quality router that is able to handle more bandwidth.
hope this helps.
cheers..