Network Configuration

Call Admission Control, Media Bypass, and E911 are three unique features that are all dependent on the network configuration defined within the Lync topology. Each of these components relies on network regions, sites, and links to be configured correctly before they can be enabled. Defining each region, each site, and all subnets might seem overwhelming at first, but it offers quite a bit of flexibility and control over call routing. The fact that the word site is used differently so many places within Lync can also be a point of confusion.

There are a few basic components one must first understand when planning for these services:

• Regions—Network regions are the backbone of a network. Each network region must be associated with a Lync Server central site (where Lync Front End Servers are deployed) defined within the topology. Network regions are typically a hub where many other network sites are connected. Examples of regions are North America and Europe, or even areas on a smaller scale such as West Coast and East Coast. In a typical MPLS-type mesh WAN architecture, a single region should be created to represent the MPLS cloud.

• Sites—Each network region consists of at least one site and possibly many more. Sites are offices or locations that are part of a network region. In other words, all the offices or locations that have users homed in the central site for the region should be created as sites. A network site object should also be created for the central site, which might seem redundant, but there is no automatic mapping of a site within the topology to a site in the network configuration.

• Subnets—Each subnet used at a site should be entered and associated with the correct site. Lync endpoints are associated with a site and region by being matched to a subnet defined here. The Call Admission Control and Media Bypass features rely on matching the subnet of the media gateway to callers, so be sure to include the subnets used for voice hardware.

• Bandwidth Policy Profiles—Bandwidth policy profiles define a network link speed and the available bandwidth for audio or video calls. The individual, one-way session limit can be specified, as well as the total amount of bandwidth used for audio and video traffic. Bandwidth policy profiles are associated with a site or region link. Sites do not require a bandwidth policy profile to be assigned. In fact, if sites within a region are not bandwidth constrained, no profile should be assigned. Assign bandwidth policy profiles only to sites that require limits on their audio and video WAN usage.

• Region Links—When multiple regions exist, region links should be defined that identify the amount of bandwidth available between two geographic regions. An example would be a North American region and a European region, each with a central site and multiple branch sites associated. A region link defines the bandwidth available between any North American site and a European site.

• Region Route—A region route specifies how two regions should be connected. In many cases, a region route mimics a region link and can just be between two different regions. In other cases in which two regions are not directly connected, but share a link to a common region, a region route defines how these regions must traverse the common region to communicate. In that case, two different region links must be crossed, which might each have a different bandwidth policy profile.

• Site Link—The final component of the network configuration is a site link. In most cases, sites are connected to a network region directly, which acts as a hub for the users. There might be instances in which in addition to a connection to the network region central site, sites have a direct connection to each other that bypasses the central site. Site links are used to create these objects that can then have a bandwidth policy profile associated.

Figure 32.8 shows a logical representation of the different network configuration components.

Figure 32.8. Logical site and region configuration.