Because this network carries data, voice, and voice that leaves the network and goes over the PSTN, there will be several different scenarios. In real networks like this one where the network we have diagramed is duplicated in multiple cities by a cable service provider even more scenarios exist. We are going to look at four scenarios, which will be plenty for us to make sure we have an understanding of the availability of this network in the more common scenarios. The four we will consider are
Data to the Internet
On net local calling
Off net local calling
Off net long distance
The following four subsections will cover the description and reliability block diagrams (RBDs) for each of those scenarios. ...