[VoiceOps] VoIP on 10mb Cat 3 switched network

[Andrew Gallo]

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On 1/4/2013 2:29 PM, Carlos Alvarez wrote:
> On Fri, Jan 4, 2013 at 12:12 PM, Simon Woodhead
> <simon.woodhead at simwood.com>wrote:
>
>> Then there's the switches. Are they switches or are they hubs? If hubs,
>> forget it. If switches, are they supporting full duplex or are you
looking
>> at 5Mb each way? Managed or unmanaged - I'd suspect unmanaged in
which case
>> you're not going to be able to do a dedicated voice VLAN or manage QoS.
>> That all points to jitter of varying degrees given either congestion or
>> simple serialisation delay.
>>
>
> I was careful to specify it would be a switched network. We'd be putting
> in new switches. The cabling is likely old, and was used with a standard
> PBX previously.
>
> My question was really about experience, not theory, and some of you
shared
> some very useful stuff. I know in theory it "should" work, and I know old
> cabling can have myriad problems. Reality often works out very different
> from theory. In all likelihood, if we took this route, it would have a
> contractual caveat that problems may be blamed on the cabling and they'd
> have to swap it out.
>
>
>
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I'll second a previous comment about hard-coding speed/duplex to
10Mbps.  While it goes against the grain (or should) for most data folks
to not use auto-negotiation, this is a case where you might run into
trouble if you leave it on. I have experience reusing "old" CAT3 for
switched ethernet (some installed for voice, some for data networking). 
The end devices will try (and is some cases may succeed) to negotiation
100Mbps; it caused nothing but trouble.  Hard coded everything to 10M
and things stabilized.  A few of the more savvy users questioned us, but
we explained the situation.

Good luck.

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