Front End Pool

A final option for branch sites is to deploy a full Front End pool instead of just a survivable branch component. This approach was historically driven by the need to place conferencing services locally, but had the additional benefit of still providing voice resiliency through backup registrar association in Lync Server 2010. Just like a survivable branch component, Front End pools could be associated with each other for backup registrar services in Lync Server 2010, and there was no limit to the number of associations a single pool could handle.

The change to requiring a 1:1 ratio between paired Front End pools in Lync Server 2013 now prevents administrators from deploying Standard Edition pools in branches and associating all of them to a single Enterprise Edition pool in a datacenter. Additionally, Standard Edition pools are not recommended for pairing with Enterprise Edition pools. Using the old approach, organizations now need to place a paired Standard Edition pool in the datacenter to provide resiliency for any Standard Edition pools deployed in branch sites.

Chapter 15 discusses the key changes in Lync Server 2013 that apply to Front End pools, but the story around the survivable branch components in Lync Server 2013 has not changed much. In fact, there are some trade-offs that are made when users are placed on a survivable branch component instead of a Front End pool. Specifically, the new service that allows replication of all user contact list and conferencing data between pools applies only when the pool is a user’s primary registrar. Since the branch component is the primary registrar, any users homed on the branch component do not benefit from the new replication service. Even if an administrator invokes a failover between two paired pools, the users homed to the survivable branch component are still in Limited Functionality mode.

The primary advantage to deploying a Front End pool in a branch is an improved conferencing experience for the local users, since the audio and video mixing happen within the branch. The other improvement with Lync Server 2013 is the capability to provide resiliency for Response Groups through the pool pairings. If a branch relies heavily on Response Groups and needs them available even if the WAN is down, a local Front End pool can still provide the Response Groups, but a survivable branch component cannot.