Technical data

DATA CENTER and CAMPUS NETWORKS DEPLOYMENT GUIDE
Deploying Brocade Networks with Microsoft Lync Server 2010 19 of 52
• Layer 3 Differentiated Service Code Point (DSCP). The value in the six most significant bits of the IP
packet header 8-bit DSCP field. It can be a value from 0 through 63. These values are described in
RFCs 2472 and 2475. The DSCP value is sometimes called the DiffServ value. The device
automatically maps a packet's DSCP value to a hardware-forwarding queue. Microsoft Lync Server
2010 supports this feature, and it is configured on each host. Typically, the host configuration is set up
through an Active Directory Group Policy so that it is configured only once, and then pushed out to all
the clients.
Given the different criteria, there are multiple possibilities for traffic classification within a stream of network traffic.
For this reason, the priority of packets must be resolved based on which criteria take precedence. Precedence for
Brocade switches follows the scheme illustrated in Figure 6.
Figure 6. QoS decision flow.
Once a packet is classified by one of the procedures mentioned, it is mapped to an internal forwarding queue. There
are eight queues, numbered 0 through 7. The internal forwarding priority maps to one of these eight queues. The
mapping between the internal priority and the forwarding queue cannot be changed.