Hello Ken,
The Linux Action Show just did a review of SIP phones. It may be helpful.
http://www.jupiterbroadcasting.com/84332/siping-on-some-linux-las-371/
I think the key is getting managed switches that can do QOS (quality of
service) that gives priority to phone/voice packets.
HTH.
CULLY Technologies, LLC
http://cullytechnologies.com
http://cully.biz
On 07/07/2015 04:00 PM, Ken Dibble wrote:
H folks,
We are going to replace our existing digital PBX phone system (which
has its own CAT3 wiring). I am desperately seeking objective
information on the issues from people who aren't trying to sell me
something. If any of you have expertise on this topic, perhaps you
could answer some questions.
My knowledge of telephony is virtually nonexistent, and my knowledge
of networking is limited.
The current PBX system manages about 150 extensions. We would like to
go to at least 200 initially, and perhaps as many as 300-350 later.
Existing phone and internet service are both currently provided by
Level 3 (formerly TWTelecom). We have fiber coming into the building
that carries both phone and internet service. Somehow, using Adtran
and PRI devices, the bandwidth ascribed to phone vs internet is
dynamically managed in response to demand. However, the internet
connection is maximum 25 Mbps down and 5 Mbps up. The system delivers
12 phone "lines". We also have a fax server with a Brooktrout fax card
that handles 20 incoming DID numbers and two outgoing (I think
"analog") lines, and it has its own Adtran device.
The computer data network has 4 48-port gigabit switches. They are NOT
POE.
Phone vendors want to sell us a VoIP internal phone system using POE
switches and our current network CAT5 cabling.
My biggest concern is network throughput and avoiding internal network
congestion.
The phone sales people have trouble understanding this concern. They
don't seem to be able to distinguish between congestion resulting from
use of the INTERnet as opposed to INTRAnet.
My network doesn't suffer from network printing, but it is pretty
busy. I am trying to get a straight answer on exactly how much of my
internal network bandwidth a very busy VoIP phone system (at times
all 12 "lines" are in use) will suck up. There are all kinds of
advantages to a VoIP system, I know, but if it slows down the data
traffic on the network I am going to be an unhappy camper.
I understand that for VoIP to be usable, its packets have to get
priority over other data traveling across the network (otherwise the
voices "break up"). This is what concerns me about the technology. If
there are 12 (or more; growth is inevitable) VoIP conversations taking
place at once across my network, what's going to happen to the
responsiveness of the constant file server access, accounting database
access, and internet access (for the fat-client payroll system and
Medicaid billing system) that is also going on across the network?
Are there options to add more bandwidth to the network? Affordable
options? For example, are there faster-than-gigabit switches that can
use the existing CAT5 (not 6) cabling? And would it matter, since the
computers only have gigabit network chips?
Secondarily, if we dispense with the Level 3 Adtran/PRI stuff and go
to SIP networks, am I going to need a lot more INTERnet bandwidth to
make that a reasonable option?
Any help on this--again, from objective sources not trying to sell me
anything--would be very much appreciated.
Thanks in advance.
Ken Dibble
www.stic-cil.org
[excessive quoting removed by server]
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