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

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Design Considerations
Planning Audio Quality
In addition, the Lync IP phones automatically mark all traffic with a Differen-
tiated Services (DiffServ) value, or DiffServ Code Point (DSCP), of 40 (101
000). DiffServ is a Layer 3 QoS protocol, and infrastructure devices can
preserve DSCPs as they route traffic or bridge it onto a WAN connection.
Therefore, you should generally preserve the DSCP in the LAN infrastructure
to ensure that the traffic continues to be prioritized over WAN connections.
However, you also need to map the DSCP to an 802.1p CoS on your switches
so that they too can place the traffic in the correct queue.
In summary, to ensure QoS for IP phones, the network administrator must
complete several simple tasks on all edge switches:
■ Configure PoE on the ports that connect to IP phones
■ Make sure that LLDP is enabled on those ports
■ Create the voice VLAN
■ Assign the voice VLAN the correct QoS priority (802.1p 5 or 6 and DSCP
40 are recommended)—Although the phones mark traffic on their own, it
is best practice to ensure that all traffic in the voice VLAN has high priority.
■ Tag the switch ports that connect to the phones for the voice VLAN. If
necessary on your switch, configure the port to trust DSCP.
E4500-24-PWR X X
E4500-48-PWR X
X
E5500-24-PWR X
X
E5500-48-PWR X
X
A3600-48-PoE E1 X
X
A3600-24-PoE EI X
X
A3600-24-PoE SI X
X
A3600-48-PoE SI X
X
A5120-48-PoE EI X
X
A5120-24G-PoE EI X
X
A5500-24G-PoE EI X
X
A5500-48G-PoE EI X
X
A5500-24G-PoE SI X
X
A5500-48G-PoE SI X
X
A5800-24G-PoE X
X
A5800-48G-PoE X
X
HP Switch PoE LLDP-MED