[cisco-voip] How to check for QoS?

Tue Jan 6 11:36:11 EST 2009

Are the two phones on the same LAN or across the WAN from each other? If they’re on the same LAN, are they on the same network segment?

From: Weigand, John V. [mailto:jvw at medicineforthedefense.com] 
Sent: Tuesday, January 06, 2009 10:34 AM
To: James Buchanan
Cc: cisco-voip at puck.nether.net
Subject: RE: [cisco-voip] How to check for QoS?

	 Litigation Management<http://www.medicineforthedefense.com/main/gifs/LMI-side-pms690wBlack.jpg> 

Serious Medicine for the Defense ® <http://www.medicineforthedefense.com/>  

	No, actually, packets coming from the opposite direction (my phone to someone else, the original was coming from a different phone to mine) are showing this:

Differentiated Services Field: 0xxx (DSCP 0xxx: Expedited Forwarding; ECN: 0x00)

0000 00.. = Differentiated Services Codepoint: Expedited Forward (0000)

	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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From: James Buchanan [mailto:jbuchanan at ctiusa.com] 
Sent: Tuesday, January 06, 2009 10:32 AM
To: Weigand, John V.; Sean Walberg
Cc: cisco-voip at puck.nether.net
Subject: RE: [cisco-voip] How to check for QoS?

Hello,

The policy-map is not the only way to apply QoS. That’s only for modular QoS. QoS can also be applied at the dial-peer level in the voice gateway or by access list, to give two examples. Do you see the same value when looking at packets from each direction?

Thanks,

James

From: Weigand, John V. [mailto:jvw at medicineforthedefense.com] 
Sent: Tuesday, January 06, 2009 9:29 AM
To: Sean Walberg; James Buchanan
Cc: cisco-voip at puck.nether.net
Subject: RE: [cisco-voip] How to check for QoS?

	 Litigation Management<http://www.medicineforthedefense.com/main/gifs/LMI-side-pms690wBlack.jpg> 

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 

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 from your computer. Thank you.

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> 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] On Behalf Of Weigand, John V.
Sent: Monday, January 05, 2009 4:02 PM
To: cisco-voip at puck.nether.net
Subject: [cisco-voip] How to check for QoS?

	Litigation ManagementLitigation ManagementLitigation ManagementLitigation 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 

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 from your computer. Thank you.

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