One-Way QoS Markings

[kfarrington]

Hi All,

Have just put the QoS configurations on the WLC for a Voice WLAN and Can see that the Phone is setting the QoS Marking on frames from the 7921G to the WLC with the following :

QoS Control

Priority: 6 (Voice) (Voice)

Ack Policy: Normal Ack (0x00)

Payload Type: MSDU

Transmit Opportunity (TXOP) Limit Requested: 0x00

But on the way back, the QoS Marking are best efforts. I also notice the EOSP change from 0 to 1.

QoS Control

Priority: 0 (Best Effort) (Best Effort)

...1 .... = EOSP: End of service period

Ack Policy: Normal Ack (0x00)

Payload Type: MSDU

QAP PS Buffer State: 0x0

or

QoS Control

Priority: 0 (Best Effort) (Best Effort)

...0 .... = EOSP: Service period

Ack Policy: Normal Ack (0x00)

Payload Type: MSDU

QAP PS Buffer State: 0x0

Can anyone understand why this would be?

Many thx indeed,

Ken

[SJessulat_2]

Hi Ken,

is the underlying infrastructure (switches, etc.) QoS-enabled, too? I.e. is the switch marking the voice-packets with the corresponding QoS-values.

Otherwise, did you follow the VoWLAN Deployment Guide from Cisco? If not, check if WMM is enabled globally.

Greets,

Sebastian

[kfarrington]

Hi Sebastian,

No the packets coming back to the WLC from the wired network are NOT marked correctly (well, reset to dscp 0).

I thought that the WLC may set the DSCP value itself when going "network downstream" to the AP?

I assume by your comments that it has to arrive at the WLC with the right classification ?

I will have to mark this :) just thought there was a clever feature of the WLC when setting the QoS profile to platinum?

I assume not, correct?

Many thx for your help :))

Ken

[SJessulat_2 · Accepted solution]

Hi Ken,

the WLC uses / translates the DSCP and 802.1p markings of the arriving packet from the LAN. So you should implement QoS in the LAN, too, anyways.

Here is the corresponding chapter from the VoWLAN Design Guide:

http://www.cisco.com/en/US/docs/solutions/Enterprise/Mobility/vowlan/41dg/vowlan_ch2.html

Figure 2-22 describes the whole translation process very detailed.

A WLAN Client supporting WMM sets an 802.1p value. When encapsulated into an LWAPP packet by the AP, the AP translates this 802.1p value to a corresponding DSCP value for the LAN Infrastructure to handle it correctly.

A packet from a non-WMM supporting WLAN Client will be set to the value which is set in the QoS-Profile on the WLC.

But if a packet arrives at the WLC from the LAN Infrastructure. the WLC uses the incoming QoS-value and translates i if needed.

Greets,

Sebastian

[kfarrington]

Hi Sebastian,

Many thx indeed for your help

Kind regards,

Ken