[asterisk-users] PoE switch recommendations?

[Gordon Henderson]

On Mon, 6 Oct 2008, Ken D'Ambrosio wrote:

> Hey, all.  We're rolling out VoIP, and I'm wondering about PoE
> recommendations, as we're going to have to replace our current network
> equipment.  My first inclination would be to just plunk down the cash and
> do a Cisco system, but I'm relatively certain that would get shot down by
> finance.  Any recommendations for a couple-hundred-port solution with
> VLANs, PoE, and QoS?  Don't care much if it's in a single chassis or not,
> so long as it has Gbit uplinks.

I'm curious as to why you want Gb uplinks on the switches?

If we assume 100Kb/sec per phone .. (gross rounding, using 100Kb/sec per 
phone, rather than ~80 - make the sums easier and builds in a margin) 10 
calls per Mb/sec.

So for a 24-port switch, 24 phones all talking to 24 extensions off that 
switch, the max the uplink port is going to be pushing out is 2.4Mb/sec.

For 200 extensions, say 9 x 24 port switches, with a single top-level (non 
PoE switch) switch with the PBX plugged in along side the 9 downlinks, 
that single PBX link will be carrying 2.4*9 = 22Mb/sec if all phones are 
in-use at the same time (and the PBX is carrying media)

Now you may not want to build the network like that, but it seems that Gb 
is overkill just for the VoIP side of things. (And with that many 
extensions, I would suggest keeping all the phones on one set of switches)

(Then again, it might not be possible to get big PoE switches without Gb 
uplinks, so it might be a moot point!)

So satisfy my curiosity - why Gb uplinks?

Cheers,

Gordon