VOIP versus PBX

["Yehuda Goldenberg" <Yehuda () nj essutton com>]

Our company is looking to replace an antiquated phone system.

I was leaning towards using a traditional PBX, because I figured that it
would be more reliable and it wouldn't be subject to the problems of IP
networks.

One vendor is trying to get me to change my mind about that. He claims
that we can keep the voice and data networks completely separate by
running vlans. The IP phones have vlan switches on them and one wire can
be run to each desk and the pc and the phone can be on separate vlans.

I was concerned that problems on the data network such as viruses would
still bring down the whole thing, and in addition to the pcs not
working, the phones wouldn't work either and it would be total mayhem.
He says that QOS would make sure that the phone calls always go through
even if the data network is completely dead.

I was also concerned that the VOIP system would mean every call - even
desk-to-desk would go through the internet and if the T1 to the internet
goes down, the phones don't work. His answer to that was redundant T1
links, and since they are the ISP and the VOIP provider, they will give
us a reliable network that won't go down. Also all the VOIP equipment on
their end is redundant.

 

What else do I have to worry about with VOIP? Is VOIP ready to replace
PBX yet, or is it too new?

 

Any help would be appreciated.