These are heady times! If you are ready to begin the preliminary design phase, it generally means that you have passed some significant milestones.
You have achieved enough of a working consensus about requirements to enable you to know what you are building, and why.
Your management has allocated enough time and money to afford a reasonable prospect of actually delivering the network you are setting out to build.
The preliminary design phase is perhaps the most intellectually stimulating phase of the design process. ...