Technical data

DATA CENTER and CAMPUS NETWORKS DEPLOYMENT GUIDE
Deploying Brocade Networks with Microsoft Lync Server 2010 7 of 52
Figure 2. Survivable branch appliance overview.
CALL ADMISSION CONTROL (CAC)
For IP-based real-time applications such as IP telephony, video, and application sharing, enterprise network
bandwidth is generally not considered a limiting factor in LAN environments. However, on WAN links between sites,
bandwidth is a finite resource. Ultimately, provisioning these links adequately is the correct approach. However, a
dependence on such network infrastructure upgrades initially can be a deployment hurdle. Upgrades to WAN links
are expensive and time-consuming. Many organizations need to experience a return on their investment in Unified
Communications firsthand before committing to WAN link upgrades. Therefore, to address UC traffic overflow, the
solution must provide an infrastructure that enables policy decisions to be made when real-time sessions are being
set up (whether or not sessions can actually be established).
When an influx of network traffic oversubscribes a WAN link, mechanisms such as queuing, buffering, and packet
drop resolve the congestion. The extra traffic is typically delayed until the network is decongested; or, if traffic is
dropped, the recipient times out and requests a retransmission. Network congestion cannot be resolved in this
manner with real-time traffic, because real-time traffic is sensitive to both latency and packet loss. This results in a
very poor quality of experience for end users. For real-time traffic, it is better to deny session requests under
congested conditions rather than allow sessions that result in a poor experience.
Bandwidth management is a solution that determines whether or not a real-time session can be established based
on the available bandwidth. The solution can also provide an alternative way to route the call when the preferred
route does not have the required bandwidth.
See the Appendix for configuration details.
QUALITY OF EXPERIENCE
Microsoft is focused on creating a Quality of Experience (QoE) based on optimizing and monitoring the user
experience. Microsoft does this by providing the following:
• A comprehensive, user-focused approach to perceived quality. Microsoft UC QoE incorporates all
significant influencing parameters (network parameters and hardware, application, psychological, and
physical parameters) to optimize the user experience in a real-life context.
• Intelligent, adaptive endpoints, including an advanced media stack. Microsoft UC is based on one of
the components of Microsoft Lync Server 2010, which provides the rich software that runs the
intelligent endpoints. It leverages underlying components, such as memory and CPU, to host
rich applications.