[asterisk-users] Switch Experiences
radamson at routers.com
Tue Sep 12 19:43:58 MST 2006
Ben Gore wrote:
> I'm would like to get feedback before finalizing design of a VOIP
> network, in particular about people's experience with network (primarily
> 10/100/1000 twisted pair) ethernet switches.
> I have a number of candidates in mind, but I would like any and all
> opinions and suggestions on the following topics:
> -Throughput/minimal latency/delays;
> -Managed vs unmanaged;
> -Redundant links/auto healing;
> -Redundant power supply;
> -Configuration of port attributes (i.e. locking 10 M/b interface to 10
> M/b instead of leaving in AUTO);
> -Resistance to Electrostatic/Electromagnetic/RF energy;
> -Shielded vs unshielded ports & cables;
> -Any other relevant information.
> The reason for asking is there seems to be a significant amount of
> disagreement about a number of these issues from a variety of "experts",
> while there's a considerable amount of experience on this list in these
> Suggestions of specific manufacturers and models welcome if you've had
> good luck with them.
What you're asking is highly dependent on the size of network. I've been
doing network performance analysis and voip readiness assessments as a
consultant for companies in 40+ states and have seen about every
combination of hardware that exits. Two examples FWIW.
A college wanted to implement voip to each of 30+ buildings using their
existing flat cisco-based network. The buildings were all interconnected
with gig fiber, however each building had workgroup type switches. Since
their gig backbone was very much under-utilized, there really wasn't a
current need to implement QoS, etc. A key element however was that every
switch was of the managed type and the college had facilities in place
to monitor dropped packets, etc, for every switch port. They implemented
a commercial voip system and are rather happy with its overall operation.
The flip side are most small businesses that purchase unmanaged switches
from the cheapest supplier they could find, and have no eyes into how
their backbone is performing. Although a small voip system might
function reasonably well, there is no way to identify disruptions (such
as dropped packets).
If you intend to purchase switches that support QoS, then dig into
exactly how QoS is implemented and you'll narrow your choices rather
rapidly. For example, there is a large number of switches that say they
support QoS, but in reality they have implemented QoS packet marking on
a per-port basis and nothing in terms of queue control (eg, no outbound
QoS queues on the ports). From a marketing perspective, they can claim
QoS support but you'd never be able to do anything constructive with it.
Most all current switches (even the cheapest models) are very reliable
(no need for redundant power supplies), transfer packets basically at
wire speeds, and are quickly moving towards a commodity item. Also, the
majority are built overseas by companies for US manufacturers. Take the
cover off any of the well-known brand-name switches and you'll find part
numbers and manufacturer's names that are very different then what is on
the front panel. (And, many of us understand contracting the build
process verses simply purchasing a large lot of pre-manufactured boxes,
Since you're asking on this list, you're probably wanting a switch that
supports QoS in some manageable form. Those that do manage QoS well
generally do all the other things mentioned on your list very well. So,
reorient the research into one of identifying those managed switches
that have implemented QoS well.
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