[asterisk-users] Which VoIP router and switch to use for medium size business

[Gordon Henderson]

On Fri, 9 Mar 2007, Zeeshan Zakaria wrote:

> Gordon, thanks for such a detailed and full of information email. It 
> helped me and must have helped hundreds of others on this mailing list.

It's quite a simplistic approach really - I think it'seasier to do 
physical separation at times than dive into the weird and whacky world of 
QoS, etc...

> In my scenario, for this client whom I am working for, their main issue 
> has always been echo. They have about 50 extensions, with 20 in the 
> office, busy office, calls all the time, up to 5 at any given time, 10 
> remote extensions and other virtual extensions just for voicemail 
> purposes. 5 IVRs and 4 queues, one VoIP line and main trunk a T1 PRI. 
> PRI is used for all incoming and outgoing calls except for long distance 
> calls where VoIP line is used.

I woudln't be sure that the echo is caused by the internal network. I'd be 
fairly sure that if you separated the asterisk box from the rest of the 
network that you'd still hear echo...

Ethernet switches do switch very well and as long as they don't have 
internal issues then 2 devices connecting point to point over the switch 
really should look like a bit of wire. You haven't said, but maybe you 
have the phones wired in-line? In which case the PC behind the phone 
talking to another PC or server on the network might well interrupt the 
phone calls, but even then I'm not sure it would introduce echo. If they 
are doing P2P down/uploading over the Internet, then unless you have a 
very high speed Internet connection (over 10Mb/sec!) then that's unlikely 
to interfere with the VoIP traffic, even without QoS.

One thing to do is make sure everything is talking the right speed though 
- make sure the ethernet switch realyl is a switch an not a passive hub. 
(if it has a collision LED then it's a hub and should be thrown in the 
bin) and make sure all ports come up at 100Mb (or 1Gb if it's a Gb switch) 
full duplex.


> I am thinking of going with HWEC and also using a good QoS switch. Right now
> there is only one switch (don't remember the name) and it is handling all
> the VoIP and data traffic. Sometimes voice breaks, and it must be because of
> interference from data traffic. But this is not a very serious problem and
> one switch with QoS should be able to handle it. Am I right here? Even if
> someone starts using P2P software.

There is a lot of information on the wiki about Echo. Mostly to do with 
analogue lines though and I've as yet, no 1st hand experience with BRI or 
PRI circuits

Start here:
   http://www.voip-info.org/wiki/view/Asterisk+echo+cancellation

> Current router is a linksys WRT54GL - Wireless-G Broadband Router. Is it
> good enough if I get a good switch? Can you suggest which switch I should
> get. I was looking on the Internet and found switches like Adtran NetVanta
> which are very expensive. What do they do which makes them so expensive? And
> in my case, is that the type of switch which I need or is there something
> cheaper out there too. I am ok without PoE.

That has a 4-port 10/100 switch and I'm guessing your internet connection 
is cable (or you have another upstream ADSL modem).

I've had good results with DLink switches and Netgear switches. Even Cisco 
switches work ok, if a shade on the expensive side. (but no-one got sacked 
for buying cisco ... yet ;-)

If you want a reasonable switch that has most features you need, I'd look 
at:

   http://www.netgear.co.uk/smart_switch_fs726t.php

but I've no 1st hand experience of them, and they're 10/100 only (with 2 
Gb ports - and I'd connect one to the asterisk box, the other to the 
router on the 'VoIP' switch, and on the other, one to a server if they 
have one and one to the router) So for 20 PCs and 20 phones, you'll need 2 
of these.

You typically pay a premium on ethernet switches for "management". This 
will give you some sort of command interface to the switch (web, serial, 
telnet) to let you fiddle with it - set link type/speeds, enable snmp 
monitoring, create VLANs, and so on. I'm not convinced of the requirement 
for this in a small office, but it may be features management desire...

If you can get the echo cracked on the office extensions out through the 
T1 line, then all ought to be fine. But if you have a lot of remote SIP 
users then you might have problems with your internet line - then you need 
to see if you can enable QoS on the router - which may help, but theres 
almost mothing you can do to shape incoming traffic, as by the time the 
rotuer see it to shape it, it's too late, as it's already come over the 
wire... So your single SIP outgoing line might suffer, as well as your 
incoming remote SIP users if you have a lot of people on the LAN doing 
heavy interweb stuff...

You might even want to start monitoring the router, if possible using 
traffic graphing software like MRTG, etc.

Good luck!

Gordon