Is VoIP reliable?

I am wondering if VoIP is reliable … Since a few weeks, the university is deploying VoIP phones in the whole campus. The good thing is that everything was apparently planned since a long time: cables were already there, just next to the regular IP cables. But since then, some problems are occurring … No connection to the “old” phone network, a whole morning without phone due to “a problem in the software controlling one of the infrastructure device”, … A few days ago, I even received an e-mail from the lab computer specialist telling all the scientists how to reset the lab firewall in case it blocks all the IP+Voice communications (for an unknown reason). I am not criticizing the deployment model of this particular case but I’m wondering how reliable is VoIP …

With “old” phones, you still have the opportunity to call emergency services even in case of total electricity failure (switches at the phone company may have to use a backup power system). Is is still the case with VoIP? After a small search on the web, the critical points in VoIP seem to be server/IP routes/routing devices redundancy, cooling and … keeping some traditional phones to the Public Switched Telephone Network 🙂