8845 video phone auto qos

[balukr]

One of our customer has bought 8845 video phones, we are trying to help on QOS for video phones on the Cisco 3850 switches. They already have Auto-QOS turned on the switches, this particular statement in the QOS doc for IOS XE 3.X concerns us how to proceed

- under Restrictions

Do not configure the auto qos voip cisco-phone option for IP phones that support video. This option causes DSCP markings of video packets to get overwritten, because these packets do not have Expedited Forwarding priority.

After this there is no recommended command what we can use for this video phones. Any insight what we need to configure on the interfaces for this 8845 video phones would be great.

http://www.cisco.com/c/en/us/td/docs/switches/lan/catalyst3850/software/release/3se/qos/configuration_guide/b_qos_3se_3850_cg/b_qos_3se_3850_cg_chapter_0100.html

Thanks.

[Mohammed Khan · Accepted solution]

Hi balukr,

 You can configure "auto qos trust dscp",Since phone support L3 marking.

Per CUCM SRND

When configuring network-level quality of service (QoS), Cisco video endpoints (including Cisco DX Series and Cisco TelePresence System devices) generally mark traffic at Layer 3 according to Cisco general QoS guidelines related to voice and video packet marking (voice media as DSCP 46 or PHB EF; desktop video media as DSCP 34 or PHB AF41; telepresence video media as DSCP 32 or PHB CS4; call signaling as DSCP 24 or PHB CS3), and therefore these devices can be trusted. In the case of personal desktop video endpoints, including Cisco DX Series devices, both voice and video media packets are marked as DSCP 34 or PHB AF41 to preserve lip synchronization during a video call.

http://www.cisco.com/c/en/us/td/docs/voice_ip_comm/cucm/srnd/collab11/collab11/endpnts.html#91177

HTH,

Regards,

Mohammed Noor

[balukr]

Hi Mohammed,

Thanks for the quick response. If customer already has "auto qos trust" command on the interface can we remove that and configure "auto qos trust dscp". Do we need any other config on the interface? In the global command do we need to modify the COS-DSCP table?

Thanks again for your help.

[Mohammed al Baqari · Accepted solution]

The config guide is correct. You need to read fully to understand why. Advice isn't to quote without full understanding. Partial reading is dangerous :).

If you scroll down to 'Example: auto qos voip cisco-phone', you will find that auto qos voip cisco-phone will create the following class-maps:

• AutoQos-4.0-Voip-Data-CiscoPhone-Class (match-any)

• AutoQos-4.0-Voip-Signal-CiscoPhone-Class (match-any)

• AutoQos-4.0-Default-Class (match-any)

• class-default (match-any)

• AutoQos-4.0-Output-Priority-Queue (match-any)

• AutoQos-4.0-Output-Control-Mgmt-Queue (match-any)

• AutoQos-4.0-Output-Multimedia-Conf-Queue (match-any)

• AutoQos-4.0-Output-Trans-Data-Queue (match-any)

• AutoQos-4.0-Output-Bulk-Data-Queue (match-any)

• AutoQos-4.0-Output-Scavenger-Queue (match-any)

• AutoQos-4.0-Output-Multimedia-Strm-Queue (match-any)

None of these class-maps match dscp af41 which is IP Phone Video (VoIP Data will match EF and VoIP Sig will match CS3 or AF31). Therefore, IP Phone Video will fall in default class which reset DSCP to 0.

I suggest to understand Auto Qos properly before applying it as it might give inverse results.

[balukr]

Yes, I will read that again. Thanks for your input.