Technical data

DATA CENTER and CAMPUS NETWORKS DEPLOYMENT GUIDE
Deploying Brocade Networks with Microsoft Lync Server 2010 18 of 52
Configure VRRP-e on default gateway routers for both the data center and campus LAN. Providing redundancy on
routers allows clients to seamlessly connect to another router within very little downtime. Note that if a voice call is in
place when the owner of the Virtual IP goes down, the phone call in most cases will drop.
Quality of Service (QoS)
Quality of Service (QoS) features are key to enabling a solid foundation for Microsoft Lync Server 2010. By Default,
Microsoft UC natively supports DiffServ through Differentiated Services Code Point (DSCP) marking by the endpoints,
which can easily be turned on or off and modified through Group Policies. A Microsoft TechNet entry
(http://technet.microsoft.com/en-us/library/dd441192(office.13).aspx) describes how to enable DSCP marking for
Microsoft Lync Server 2010. This includes: enabling QoS, installing the QoS Packet Scheduler on computers, and
verifying Group Policy settings on computers. QoS is honored by default on Brocade switches when the command
trust dscp is used.
QoS provides the ability to prioritize designated traffic over other traffic in a switch. The QoS associated with
synchronous traffic such as audio or video can be affected by delay, jitter, and packet loss. Microsoft Lync Server
2010 has been designed to work without any QoS, but when traffic demands increase and Service Level Agreements
(SLAs) are put in place, QoS is one of the most critical elements in the network. When QoS features are enabled on
Brocade switches, traffic is classified as it arrives at the switch and handled on the basis of configured priorities.
Traffic can be dropped, prioritized for guaranteed delivery, placed into a best-effort queue, or be subject to limited
delivery options. Traffic can also be controlled by leveraging rate limiting features that come with the Brocade
switches. Rate limiting limits the amount of bandwidth a certain type of traffic can use.
Classification is the process of selecting packets on which to perform QoS, reading the QoS information, and
assigning a priority to the packets. The classification process assigns a priority to packets as they enter the switch.
These priorities can be determined on the basis of information contained in the packet or assigned to the packet as
it arrives at the switch. Once a packet or traffic flow is classified, it is mapped to a forwarding priority queue. Packets
on Brocade devices are classified in up to eight traffic classes, with values from 0 through 7. Packets with higher-
priority classifications are given precedence for forwarding. Typically, voice requires a classification between 4 and 6,
while video requires a classification in the range of 3 through 5, to ensure that enough resources are reserved. In
addition, you should configure rate limiting so that voice and video data does not saturate the link.
Configuration Options for QoS
The trust level in effect on an interface determines the type of QoS information the device uses for performing QoS.
The Brocade device establishes the trust level based on the configuration of certain features if the traffic is switched
or routed. The trust level can be one of the following:
• Ingress port default priority. Not a recommended option for a Microsoft Lync Server 2010 environment,
because it assigns the entire port a priority and does not distinguish between data, voice, or video. In
addition, the port priority command never affects the DSCP value of the packet. It is used only to assign
internal prioritization for egress queueing and to assign the 802.1p value when a packet comes in
untagged without a tagged interface.
• Static MAC address. Allows the user to control the priorities assigned to traffic based on the destination
MAC address. This is not also recommended, due to the overhead in management.
• Access Control Lists. ACLs can prioritize traffic and mark it before sending it to the next hop. Since this
option is the most granular and suited for UC, it will be discussed in detail later.
• Layer 2 Class of Service (CoS) value. This is the 802.1p priority value in the Ethernet frame. It can be a
value from 0 through 7. The 802.1p priority is also called the Class of Service.