Web Services FQDN Overrides

When creating a Director pool in the Topology Builder, the web services FQDNs are automatically provisioned with an option to override the internal and external FQDNs. When a single Director is deployed, overriding the FQDN is generally unnecessary, but when multiple Directors are deployed, it might be necessary to change the URLs depending on load-balancing methods.

If a traditional load balancer is used for the SIP, HTTP, and HTTPS traffic, it is acceptable to use the pool FQDN suggested by the Topology Builder. This works great because all of the traffic is destined for the same virtual IP hosted by the load balancer. This kind of configuration is shown in Figure 9.5.

Figure 9.5 Using a Hardware Load Balancer for Director Traffic

Within Lync Server, a DNS load balancing for SIP traffic option exists, but a hardware load balancer is still necessary for balancing HTTP and HTTPS traffic. This configuration means that there is a split in the services and one FQDN must resolve to the pool for SIP traffic and another FQDN is necessary for the web services traffic. These two FQDNs resolve to different locations; the pool name always resolves to Director pool member servers and the web services FQDN resolves to a load-balancer virtual IP. This kind of scenario is shown in Figure 9.6.

Figure 9.6 Using a Combination of DNS and Hardware Load Balancing for Director Traffic

The web services can also be configured differently for internal and external traffic depending on existing infrastructure. For example, an organization might use a combination of DNS load balancing and a hardware load balancer for all internal pool load balancing, so overriding the internal FQDN is required internally.

In this example, consider a reverse proxy scenario where the reverse proxy has its own form of built-in load balancing such as with Microsoft Forefront Threat Management Gateway. It can resolve the web services directly to the pool FQDN because SIP traffic is not carried through the reverse proxy. A reverse proxy sending external traffic to the Director pool that uses a load balancer internally is shown in Figure 9.7.

Figure 9.7 External and Internal Web Services Names