This depends on what you are looking to do and what hardware you have. If you are using the StrongMesh/XBus system and would like to keep everything on a LAN, the Command Center would be your preferred solution. If you want to be able to access the Command Center from multiple places you can set up a VPN to the machine running the Command Center. Alternatively if you do not wish to setup a VPN and still want to be able to access your setup remotely you can sign up for the netx-web service. You may also access your system remotely in the Command Center using the WAN IP addresses of your controllers.
If you are using our Wi-Fi or Ethernet thermostats and want to connect using a LAN you will want the NetX-IP Command Center. You may also setup a VPN for the IP Command Center to access it from multiple places. If you want to connect through the WAN there are multiple options available. You can use the direct connect service by claiming your device and logging into the DirectConnect page on the Network Thermostat website. There is also the CloudConnect service that will allow you to connect using the Cloud. Finally you can use the WAN IP addresses in the IP Command Center to access the system remotely.
For more information, feel free to contact a solutions specialist to help you work through the wide array of options.