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QoS for Micrsoft OCS configuration


My company is getting Microsoft OCS (Unified Communication) installed, and therefore I need to configure QoS for Voice And Video. It's gonna be softphone (Microsoft Office Communicator) so I cannot segment the Voice and Video traffic into sepereate VLAN's, the Voice/video data is gonna flow on the normal Data VLAN.

The Clients (Microsoft Windows vista and 7 PCs) can mark the IP packets for voice/video with a DSCP value (

All of our switches is HP and all of our routers is Cisco.

We have 9 departments, all with some Access layer switches (HP) that connects to a Cisco router, the routers then connect to our Core Switches in the Datacenter.

My question is...:

Do I need to mark the traffic with som COS values on the Access switches, or should I just create some LLQ queues on the routers that match the DSCP value from the Client? Can the DSCP value in the IP packet go from the client though the Access switche (layer 2) and still remain their DSCP value when hitting the routers?

Correct me if i'm wrong, but as I have understood it, is it not possible to make any QoS / traffic priority on a layer 2 switch, it's only possible to mark traffic. But when my clients are marking the traffic, i dont see why i should do any COS (layer 2 marking)

So will it be enough to just match the DSCP values on the routers, without any switch config.

Regards, Steffen - Denmark.

Cisco Employee

Re: QoS for Micrsoft OCS configuration


It is up to how HP switch handles traffic from softphone.

If they keep DSCP values from softphone or pC and deliver to router without any change, then you can create router QoS policy based on DSCP from softphone.

If HP Switch reset DSCP to 0, then you need to create router policy to mark VoIP traffic with proper DHCP based on source IP or destination IP.

In CISCO SW, you can make SW to trust DSCP from PC or IP phone but I am not sure if there is a way to do same thing on HP SW.


Community Member

Re: QoS for Micrsoft OCS configuration

Thanks for your answer!

But it's it correct understood that a layer 2 device cannot make any QoS/traffic priority, they can only mark traffic with COS values 802.1p right?

On the other hand I see a problem in trusting DSCP directly from the clients, they could manipulate with the ip packet and send wrong DSCP values with traffic that should not have high priority - right?


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