HP Survivable Branch Communication zl Module powered by Microsoft Lync Planning and Design Guide 2011-02

2-26
Design Considerations
Planning Audio Quality
■ Map DSCP 40 to 802.1p 5 or 6, which configures the switch to place the
traffic sent by phones in the correct priority queue.
■ Enable the minimum number of queues required—Remember, having
fewer queues gives each queue greater buffer space. However, you need
one queue for each type of traffic that requires different handling.
You must complete similar tasks on uplink switches:
■ Extend the voice VLAN throughout the network.
■ If necessary on your switch, configure the switch-to-switch links to trust
DSCP.
■ Map DSCP 40 to 802.1p 5 or 6, which configures the switch to place the
traffic sent by phones in the correct priority queue.
■ Enable the minimum number of queues required.
Lync Softphone. The Lync softphone (the client that runs on a Windows OS)
does not use LLDP-MED, and the voice traffic is placed in the same VLAN as
the rest of the computer’s traffic. To protect the VoIP traffic, you must ensure
that the traffic is marked with a QoS value. Generally, you should do so by
configuring the Lync client to set the value.
If your branch users have already been using Lync or OCS 2007 R2, you might
have already completed this configuration. Otherwise, you must do so now.
You can establish the settings through group policy objects (GPOs) to speed
configuration. The basic requirements are:
■ QoS is enabled on the Lync Servers and the SBM.
You can enable QoS with the Set-CsMediaConfiguration Lync Server
Powershell cmdlet.
■ QoS is enabled on the Lync Server client.
■ The computers’ network adapters (network interface cards, or NICs) have
the QoS packet scheduler installed.
■ The GPO Computer Configuration > Policies > Administrative Templates >
Network > QoS Packet Scheduler > DSCP value of confirming packets policy
is correctly configured:
•For Guaranteed service type, which is the type assigned to all audio
traffic by the Lync client, the setting is Enabled with a value of 40.
•For Controlled load service type, which is the type assigned to video
traffic by the Lync client, the setting is Enabled with a value of 24.