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QoS on Cisco routers / switches

Posted on 2011-03-23
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Last Modified: 2012-05-11
I am implementing a non-cisco voip solution on a cisco routing / switching infrastructure.

Our infrastructure is large. Voice traffic will travel across router(s) on our local lan.

QoS is currently not enabled in any way on our infrastructure.

Please provide examples / explain what configuration will need to be put on our cisco switches / routers in order to prioritize voice traffic as it travels from the access port, to the router, and back to the voip servers, etc.

I'm not looking for anything elaborate, only how to tag traffic coming in a port on a specific (voice) vlan and how to insure prioritization as it travels across the network.

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Question by:c-h-r-i-s-t-o-p-h
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Expert Comment

by:Ernie Beek
ID: 35205277
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by:koudry
ID: 35300968
Hello,

Although you have not specified this in your question, I assume you want to host both data as well as voice and make sure that voice is prioritised and protected during network congestion. Is this correct?

(1) Have separate networks

So assuming you want to host voice and data together, you will have to separate both traffics, using dedicated network for your voice traffic and another dedicated network for your data traffic. So that is the first thing to do.

(2) Tagging your untrusted traffic, i.e. traffic from the customer network

The way traffic is processed depends on where they originate. If the traffic comes from the customer network, it is treated as untrusted. From QoS point of view, untrusted traffic is classified based on it network.  Once the traffic is classified, it will be marked accordingly.

Data traffic is marked as AF (Assured Forwarding) which will have the values of AF4(DSCP 34), AF3(DSCP 26), AF2 (DSCP 18), AF1 (DSCP 10) with Internet traffic going to the default or best effort queue. So your data traffic is clearly marked this way.

Your voice traffic is marked as EF (Expedited Forwarding) or DSCP 46.

(3) Processing trusted traffic or traffic from the core network

You need QoS policies on your core router to honor your inbound traffic, i.e. traffic going to the customer network otherwise your inbound traffic will suffer, i.e. your voice quality will be impacted as there won't be a protection.  If you do not own the core network, then you will have to speak to whoever owns it.

As traffic from the core network is said to be trusted, the way it is processed is different. The classification is based on DSCP value as opposed to the source or destination network. I will show this in the configuration.

So that is the theory or principle. I am now going to find some config for you.

Thanks.
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Author Comment

by:c-h-r-i-s-t-o-p-h
ID: 35301351
Thanks. I plan to have both data and voice on each user access port. I am very curious as to config examples for tagging traffic as well as policy at the router.
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koudry earned 500 total points
ID: 35302691
Hello,

I need to design 3 QoS policies of which two will be used on the customer premises equipment (CPE) and the third will be used on the core router. I have done the first one which you can try out while I do the remaining two.

Thanks. sample-voice-data-qos-CPE-outbou.doc
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Expert Comment

by:koudry
ID: 35303029
Hello,

This is part 2 which takes care of the second policy, i.e. inbound policy to be applied to the CPE inbound. I have one more to do and once that is done, I will pull all the config together.  If the solution I am proposing does not work, we will wait for some else to come with something better.

Thanks.

 sample-voice-data-qos-CPE-inboun.doc
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Expert Comment

by:koudry
ID: 35303055
Hello,

You may also want to look at this:

Quality of Service Interactive Voice Network Configuration Example @ http://www.cisco.com/en/US/products/sw/voicesw/ps556/products_tech_note09186a00807f8b33.shtml

Thanks.
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Expert Comment

by:koudry
ID: 35316252
Hello,

I have now done a sample core router QoS config. This is not a fixed order of things as the same thing can be done in various ways. For the purpsoe of the sample config, I have used the QoS default or Best Effort (BE) queue for data. In a scenario where there are several applications, it is better to use AF (Assured Forwarding) broken down as AF1, AF2, AF3 and AF4. Default or Best Effort can then be used for Internet traffic.

There is also some info @ http://www.cisco.com/en/US/tech/tk652/tk698/technologies_tech_note09186a0080094660.shtml.  

I am sorry if I have confused you.

Thanks.

 Koudry---Cisco-VoIP---sample-QoS.txt
sample-voice-data-qos-core-route.doc
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