For most businesses, VoIP offers a compelling business argument. Merging the voice network with the data network means only implementing one hardware and wiring infrastructure. VoIP systems are easier to administer and maintain that traditional PSTN phones. The list goes on and on.
VoIP is not without its issues though, one of which would be having all of your proverbial eggs in a single basket- the network. Hopefully an enterprise network is relatively stable, but you still have to consider the possibility of a complete network outage and what that does for communications. Certain fields- emergency response, medical care facilities, banking and finance, etc. – can not afford to be without communications even for a minute. A recent ZDNet article addressed some of these concerns.
There is no way to truly guarantee that communications will be available 100% of the time. However, if the weaknesses of the network and the VoIP communications are properly considered and addressed I believe that a very high availability can be achieved. The technologies and level of redundancy required to achieve that availability are costly though and add to the TCO (total cost of ownership) of the VoIP solution and impact the ROI (return on investment), possibly negating many of the VoIP advantages and making the case for VoIP a harder sell.
Regardless of the industry that VoIP is being implemented in, sound network security practices should be followed. For VoIP networks, segmenting VoIP traffic on separate VLAN’s and encrypting voice communications provide additional security. However, enterprises should also consider the potential for a network-wide outage making VoIP unavailable and have a written policy for how to handle critical communications in the event that such a catastrophe occurs.