Apple Cache Service
For best operation on the emPSN network, it is important that you configure your Apple Cache server inline with article HT5590 – http://support.apple.com/kb/HT5590 – particularly defining the local IP address ranges of your network. Failure to set this correctly could cause your service to be ineffective or not operate at all.
lcdn-registration.apple.com is used in the registration process. Controlling the use of this URL can control what can register on your network.