Siemens's Bishop says: "10 Mbps ethernet is dirt cheap and adequate for a voice only network."
This is an approach which particularly works for companies mainly interested in IP to cut down on the costs of provisioning employees, he says.
"We have some clients in professional services who are often moving teams and phones and the costs of moving and changing are extraordinary for them," says Bishop.
Many companies considering the idea of converging all data onto one network can't quite believe it will be reliable enough.
Rightly or wrongly, data networks aren't seen as being the most reliable things in the world. And if something should happen to the data network, workers want to be able to know they can pick up the phone and call the help desk. When they pick up the phone and there's no dial tone, it becomes a very serious problem.
So there's a perception, justified or not, that phones which are running on a potentially dodgy data network won't have that cast-iron, unshakable, "fine-nines" reliability that we're used to from conventional telephone networks.
Of course, the reliability of any given network doesn't just depend on the technology. It's as much if not more a function of network design. The more redundancy and fail-safe features you build in, the more reliable it will be.
But that comes at a price and obviously the more you spend on a network, the less attractive the cost-benefit analysis becomes -- as saving cash was the reason for converging your networks it in the first place.
To an extent, it's more a question of psychology than science. Putting all your eggs in one basket just feels unwise, particularly if that basket is as shaky as the average enterprise data network.
Ian Cox, principal analyst at research firm TelecomView, says: "If you talk to an IT manager about a network with five-nines' reliability, they would look at you strangely."
Siemens' Bishop says: "We have clients whose network design allows for two separate networks. For some of them there are security concerns. They want to protect their voice network from everything that is going on over their data network."
Telecoms equipment vendors argue such an approach is wrong.
Continued ...
