[cisco-voip] How to check for QoS?

[Jeff Garvas]

John,

Look at one of your switches for class-maps that match traffic and
policy-map statements that define classes and set or trust dscp values.
(trusting dscp can be defined at the port too).   In this example we're
trusting dscp assigned by the phone if its already dscp ef.

class-map match-any VOICE
  match ip dscp ef

policy-map QOS-MARKING
  class VOICE
    trust dscp
  class class-default
   set dscp default

This specific example is being applied "at the vlan" on a 3560 series, so
you'd also see:

interface Vlan100
 service-policy input QOS-MARKING

and something like this:

interface range FastEthernet0/1 - 48
 mls qos vlan-based

The packets would in fact be marked and you could detect it in a packet
capture if the marking is being maintained throughout the network.   However
just because the marking is there doesn't necessarily mean any specific low
latency queuing is being applied anywhere to give precedence to RTP packets
over say bulk data / scavenger or unclassified default traffic. There are
multiple things you're going to want to look at or have your vendor explain
how they implemented it and what percentages of bandwidth they've allocated
to each class of traffic.

-Jeff



On Mon, Jan 5, 2009 at 5:01 PM, Weigand, John V. <
jvw at medicineforthedefense.com> wrote:

>    [image: Litigation Management]
>
> Serious Medicine for the Defense (R) <http://www.medicineforthedefense.com/>
>
>  I've been tasked with checking to see if our VAR ever setup any QoS at
> all, and if so, what type and how it's set. Unfortunately, although I've
> become fairly proficient at CallManager itself, I'm pretty new to the inner
> workings of everything at the actual network level.
>
>
>
> I know there's a few different ways to set it all up, and I've tried poking
> around, but I'm not really even sure where to begin looking. Does anyone
> have any pointers as to how I might be able to track down some of this info?
> Is there anything I can tell from a packet capture of a call from between
> two of our sites? I do also have read only access to the switches/routers on
> the network.
>
>
>
> Thanks in advance!
>
>  *John V. Weigand*
> Help Desk Support/Executive Support
>
> Litigation Management, Inc.
> 300 Allen-Bradley Drive
> Suite 200
> Mayfield Heights, OH 44124
>
>
>
>
> Tel: 440-484-2000
> Fax: 440-484-2009
> Cell:
> email: jvw at medicineforthedefense.com
>
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