Time Machine was designed to work with locally attached storage or storage attached to either Apple’s AirPort Extreme or Time Capsule products.  That said, it’s not that hard to make it work with any old NAS solution.  Here are the steps from a terminal window:

1. Enable support for unsupported disks via: defaults write com.apple.systempreferences TMShowUnsupportedNetworkVolumes 1
2. Create a SPARSEBUNDLE.  To do this, you need to create it on your local volume.  The command is: hdiutil create -size XXg (XX = size in GB) -type SPARSEBUNDLE -nospotlight -volname “Name of your Backup” -fs “Case-sensitive Journaled HFS+” -verbose ./Computername_MACaddress
3. To find out the MACADDRESS just use: ifconfig en0
4. Copy the bundle and all of it’s subdirectories to the root of the NAS share.

Once you point Time Machine to the share, it will find the SPARSEBUNDLE and use it for backups.