DComTalk.com

All,

What is the perceived wisdom regarding PoE, Ethernet switches and
sharing a switch between IP phones and PC's in a small office?

I can get a 24 port switch, where the first 12 ports are PoE enabled.
This would be a neat, cost effective solution for a couple of small
sites I have with (up to) six desks.
The VoIP provider has specified that there should be separate switches
for PC's and the phones. Whilst I can see this as a 'KISS' solution, I
do not agree with their argument that PC traffic will affect phone
traffic.
The backplane can cope with 8.8GB throughput, and a switch-based LAN
does not have the latency of a hub-based LAN.
In an office of this size, I cannot see that there would be a problem
with this arrangement, but I have no experience of a multi-phone IP
based solution.

There will be two ADSL lines, and routers. One for Internet access, the
other for the VoIP service.

TIA,
Phil Partridge
philp@pebbleGRIT.demon.co.uk
Remove the grit to reply

The problems are twofold. PoE switches are all or nothing critters.
I've
never seen one that only had power on some of them.
The other is the bursty nature of traffic, both data and voice.
Lets draw a scenario.
Everyone's using the phone, and one of your power users brings in a
DVD of the newest hit movie, and decides to share it with everyone in
the office. Boom! The backbone ( unless everything is on the same
switch) is now saturated with movie, and all your phone conversations
start to sound like an alien as packet loss, jitter and so on take their
toll on voice quality.

--Dale

The problems are twofold. PoE switches are all or nothing critters.
I've never seen one that only had power on some of them.

See the current Netgear lineup.. several of their low/mid-tier switches offer
some POE ports, including a 8-port switch with 4 POE enabled ports, (FS108P),
and a 24 port with 12 POE (FS726P).



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Two different switches will not necessarily resolve the problem if the IP phones and computers are all on the same subnet. You could easily use one switch for everything and simply employ VLANs. Assuming the office has only six people in it and all are connected at 100mbs there will most likely be no problem. Now if the IP phones are going over a VPN or the internet to connect to the PBX then you might have a problem. This problem is most easily resolved with greater up/down bandwidth but you could also employ QoS to prioritize the Voice packets.