The other key point about failures is how do users leave the network? How do they get in or out? With typical mesh networks there is only one way in or one way out. Think of it as one door. With Thread, users have the notion of a border router. They can have as many border routers as they want. Typically there are two, but there can be more. The nice thing about a border router is just like a house that has multiple doors, users have multiple ways in and out of that network so they never have to be worried about being cut off if someone takes away or boards up one of the doors.