After you have collected your users' requirements and evaluated potential topologies, you might be tempted to jump ahead to procurement and implementation. Before you do that, you should address just a few more issues. You must still
Determine what the aggregate traffic loads will be across your WAN's backbone (if there is a backbone).
Identify where to place inbound and outbound gateways (such as dial-in modem pools or gateway routers that connect the network to external networks).
Select the transmission technologies that will be used for each link.
Identify IP addressing and subnet masking schemes.
Select which routing protocol(s) will be used.
A WAN backbone is a router, or routers, and ...