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Beginner

Does Cisco IP Communicator support 802.11e WMM QoS tagging

Dear community,

Just a lean and mean quick question which I don't seem to find the answer for in any doc:

Does the CIPC (Cisco IP Communicator softphone application on Windows) support 802.11e WMM tagging?

As you may know, this is the most critical point in the end-to-end QoS design for priorizing the Voice traffic.

Thanks in advance,

Dion Dohmen

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VIP Mentor

This is depend on the what is

This is depend on the what is the end point (tablet, phone, laptop,etc). Most of them DSCP value marked as EF for those application, but whether that convert to UP value of 6 is entirely upto end point. (most of them don't properly map it)

Here is some of the test results I have done few years back

https://mrncciew.com/2013/01/08/byod-with-qos/

Refer this post to see how Cisco is going to address this in latest codes

https://supportforums.cisco.com/discussion/12934171/wireless-qos-marking-issue

HTH

Rasika

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Beginner

Hi Rasika,

Hi Rasika,

Thanks, I have already read your posts on mrncciew, great posts btw :)

I have seen wireless pcap's from our customer, where they have marked the voice packets using the Group Policies  (DSCP46) within windows. In this same pcap I could see that the UP value was Best Effort, too bad.

I can't find any information on how to influence this UP marking from a windows machine? Is this purely dependant on the application, which is Cisco IP Communicator, or can Windows or NIC drivers play any part in this, so that the UP value is actually marked as voice traffic?

The reason being, and that's the same conclusion as I've read in your post, that this first hop (from Wireless NIC laptop to AP, is the most important part in the end-2-end QoS path.....

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VIP Mentor

I can't find any information

I can't find any information on how to influence this UP marking from a windows machine? Is this purely dependant on the application, which is Cisco IP Communicator, or can Windows or NIC drivers play any part in this, so that the UP value is actually marked as voice traffic?

Since many devices do not correctly mark UP value, Cisco is going away from trusting those UP values. Instead, they will use DSCP value of original IP packet to derive the CAPWAP header DSCP value in latest code of AireOS (currently this value is derive from the UP value of wireless frame).

If you look at the below thread carefully you will find how that works. Read that IETF draft linked to that thread for better understanding those proposed changes

https://supportforums.cisco.com/discussion/12934171/wireless-qos-marking-issue

HTH

Rasika

*** Pls rate all useful responses ***

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Beginner

hi Rasika,

hi Rasika,

I understand Cisco is going away from trusting the UP values and instead using the DSCP markings, but nevertheless, how will the end host (windows machine in this case) handle the priorization of the wireless voice packets leaving the wireless network card?

802.11e WMM at the end station uses the following to priorize voice packets over other data packets:

With EDCA, high-priority traffic has a higher chance of being sent than low-priority traffic: a station with high priority traffic waits a little less before it sends its packet, on average, than a station with low priority traffic. This is accomplished through the TCMA protocol, which is a variation of CSMA/CA using a shorter arbitration inter-frame space (AIFS) for higher priority packets.

In my opinion, this is the first and most important hop in the QoS path right?

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Beginner

Rasika,

Rasika,

check this:

To compensate for the possible incorrect or unexpected markings, AireOS controller code 8.1MR1 offers the possibility to configure a customized DSCP to UP, and UP to DSCP translation table. You can also trust the DSCP marking on the client 802.11 upstream frames, instead of the 802.11e UP marking.

This would be perfect. We can influence the CIPC traffic leaving the workstation by using QoS Policies within the Windows Group Polices, and mark these packets with DSCP46. Next, the AP will use these DSCP markings instead of the UP value, to map it to the outer CAPWAP header.

But then again, I am curious if the wireless network interface within the end station, will priorize the upstream traffic using EDCA based on purely the DSCP values?

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