[cisco-voip] QoS and network guys

[Nick Matthews]

I think it's fairly simple - the value of L2 QoS isn't as high as WAN.

1. L2 QoS is at least an order of magnitude more difficult. Buffers,
DSCP/COS concerns, hardware dependent, dozens of lines of configuration
(see AutoQoS outputs) potentially.
2. L2 QoS really comes into play during loops, viruses, or oversubscribed
trunk ports. These aren't that common.
3. It's quite easy to mess up or cause problems. If you forget to trust a
port, everything is 0 on many platforms. Sometimes QoS causes odd issues on
ports that would otherwise be fine. For example the default queues with
AutoQoS can cause bandwidth problems because of a more limited queue for BE
traffic compared to the default.

It's best practice and you should do it, because that's one less thing that
can cause voice quality problems. But there are valid reasons to being
hesitant to L2 QoS. I think as more video is deployed it will become more
important, since video bandwidths can start taxing uplinks and ports more
easily. And at that point the configuration isn't much different.

-nick


On Mon, Sep 16, 2013 at 3:33 PM, <A.L.M.Buxey at lboro.ac.uk> wrote:

> Hi,
>
> >    It's more about protecting voice traffic from unforseen traffic spikes
> >    because we have a very large amounts of data transfer.
>
> true - though I've tested VoIP across a 3:1 contended 1G pipe and whilst
> there
> was an interesting delay to the call (notable because both handsets were
> in the same
> room rather than other end of country) there was no jitter...so the call
> was fine.
> no bubbling, gurgling, squeaks etc etc - I guess it depends on what TYPE
> of transfer
> is going on. I'm sure some nice 'very efficient' P2P protocol would do
> more damage
> than pure HTTP/FTP which will do its nice window scaling and fallback.
>
> >    It isn't like I'm asking the guys to come up with something new and
> >    untested.  I'm asking them to implement what we already have in
> Europe and
> >    Asia.
>
> well then. no excuse :-)
>
> alan
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