[cisco-voip] How to check for QoS?

Wes Sisk wsisk at cisco.com
Tue Jan 6 15:05:53 EST 2009 

Hi John,

There are many facets to QoS.  I recommend you grab a six pack of 
caffeine, a quiet room, and the QoS SRND.

Regards,
Wes

On Tuesday, January 06, 2009 10:28:37 AM, Weigand, John V. 
<jvw at medicineforthedefense.com> wrote:
>
> 	
>
> Litigation Management
>
> 	
>
> Serious Medicine for the Defense ® 
> <http://www.medicineforthedefense.com/>
>
> 	
>
> 	
>
> Thanks so much for everyone’s input, it’s very much appreciated!
>
>  
>
> “show policy-map” on both our voice and data routers is returning with 
> nothing, so I’m taking that to mean we don’t have any policies applied 
> on those.
>
>  
>
> I was able to get the packet capture into Wireshark, and the RTP 
> packets are showing the following:
>
>  
>
> Differentiated Services Field: 0xb8 (DSCP 0x2e: Expedited Forwarding; 
> ECN: 0x00)
>
>                 1011 10.. = Differentiated Services Codepoint: 
> Expedited Forward (0x2e)
>
>  
>
> Based on my very limited knowledge, that does look like we’re applying 
> QoS somewhere? If that is the case, would it be applied at the 
> switchports?
>
>  
>
>
>
> 	*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 
> <mailto:jvw at medicineforthedefense.com>
>
>
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> *From:* Sean Walberg [mailto:swalberg at gmail.com]
> *Sent:* Monday, January 05, 2009 5:37 PM
> *To:* James Buchanan
> *Cc:* Weigand, John V.; cisco-voip at puck.nether.net
> *Subject:* Re: [cisco-voip] How to check for QoS?
>
>  
>
> If you get the packet capture into Wireshark, you can (in addition to 
> checking for the DSCP == EF) measure the latency to see if QoS is 
> doing its job.
>
> >From a router, though, you can check your policy maps with "show 
> policy-map" or "show policy-map interface", it will tell you if a 
> policy is applied and what it's doing.  You're looking for a priority 
> queue.
>
> The Cisco QoS SRND is a good way to understand QoS.  It's hefty, but 
> most of the details are duplicated for every model of switch.
>
> Sean
>
> On Mon, Jan 5, 2009 at 4:07 PM, James Buchanan <jbuchanan at ctiusa.com 
> <mailto:jbuchanan at ctiusa.com>> wrote:
>
> Hi John,
>
>  
>
> The biggest thing you are looking for is that the voice traffic is 
> being marked and that the marking is being recognized throughout the 
> network.  A packet capture is the quickest way to determine this. In 
> the packet capture, you will see a field for Differentiated Services. 
> For traffic that is the actual audio payload, you should see the 
> Differentiated Services field as Expedited Forwarding. You will want 
> to check packets going in each direction.
>
>  
>
> On the switches, for ports that have a phone plugged in you should see 
> that the switchport is configured to trust cos and is configured to 
> trust based on the device being a cisco phone (mls qos trust cos and 
> mls qos trust cisco-phone). What these commands look like can vary 
> according to the model of switch.
>
>  
>
> For any connection that is a voice server or voice gateway, the 
> switchport should trust the dscp value (mls qos trust dscp). This 
> should also be true on uplinks from switch to switch and from switch 
> to WAN router.
>
>  
>
> On the WAN router, depending upon the speed of your connection you 
> should be using some sort of low latency queuing and/or traffic shaping.
>
>  
>
> Thanks,
>
>  
>
> James
>
>  
>
> *From:* cisco-voip-bounces at puck.nether.net 
> <mailto:cisco-voip-bounces at puck.nether.net> 
> [mailto:cisco-voip-bounces at puck.nether.net 
> <mailto:cisco-voip-bounces at puck.nether.net>] *On Behalf Of *Weigand, 
> John V.
> *Sent:* Monday, January 05, 2009 4:02 PM
> *To:* cisco-voip at puck.nether.net <mailto:cisco-voip at puck.nether.net>
> *Subject:* [cisco-voip] How to check for QoS?
>
>  
>
>
> 	
>
> Litigation Management
>
> 	
>
> Serious Medicine for the Defense ® 
> <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 
> <mailto:jvw at medicineforthedefense.com>
>
> 	
>
>
> PRIVILEGE AND CONFIDENTIALITY NOTICE
>
> The information in this electronic mail is intended for the named 
> recipients only. It may contain privileged and confidential material 
> and may be protected under law by the Health Insurance Portability and 
> Accountability Act. Any use of this information by anyone other than 
> the intended receiver is prohibited. If the reader of this message is 
> not the intended recipient, you are hereby notified that any 
> dissemination, distribution, copying, or other use of this message or 
> its attachments is strictly prohibited. If you have received this 
> message in error, please notify the sender immediately by replying to 
> this electronic e-mail or by calling (800) 778-5424. Please delete it 
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>
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> -- 
> Sean Walberg <sean at ertw.com <mailto:sean at ertw.com>>    http://ertw.com/
>
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