By relling on Jan 16, 2007
The recent disruption of the internet connection between Taiwan and the mainland is an example of a system where there is not much diversity. This is a rather large scale example, perhaps one of the largest such examples on earth. The lesson is that the diversity in your design needs to be able to cover the expected fault (pun intended) zone. In this case, what was lost was capacity, the international connection capacity was reduced to approximately 50%.
Another, more local example of diversity in communications recently occurred to my colleague, Mike Anuta, in Wisconsin. A construction accident severed the underground fiber link. This resulted in disconnecting the local area from the rest of the world. Mike says the accident also clobbered a bunch of the cellular service. Being a clever engineer, and having a working internet link, Mike was able to access the most important application at Sun, e-mail. The big question is whether it is also worth the cost to add a VOIP account, if the pricing was reasonable. So, this is another example of how you can work around systems faults using diversity. Remember, you can run IP over almost anything from cups-n-strings to radio links to fiber -- all using a protocol (IP) designed to overcome link faults.