Phone dude

When the phone gets plugged in, you assign it an IP. From that IP it sends out on the Broadcast address looking for other similar phones of the same release. You can choose to join an existing "group", or create a new one.

This system can work in a WAN cloud, but you need to set up a VPN connection and set the user up for "remote worker"

Each phone has a built in 20 minute mailbox. If 2 or more phones are in the same group, the is an AA available (500). Each phone is set up with a 10 minute backp voicemail. Lets say bob at ext 210 lost his connection to the router and no longer can receive calls. The other phones in that group will use their 10 minute reserve to save bob's voicemails until they see his phone come back online. Once it does, they transfer the voicemails to Bob's phone.

Hope this helps. There is some great documentation on the Avaya web site as well.