Hardware load balancers are devices that often combine an Ethernet layer 3 switch with the ability to load balance, and switch multiple streams of traffic, such as client to server, server to server, server to Active Directory, server to DNS, and management access to server pool. They are sophisticated devices that feature extensive monitoring capabilities; operate at multiple gigabit levels; generate powerful load balancing metrics that can be configured to route traffic based on such conditions as least connections on a server, the latency times of servers, weighted round robin or weighted least connections. A load balancer exposes a single VIP (virtual IP) address to clients so that they do not directly access individual Enterprise Edition Front End Servers. A load balancer is not required to decrypt TLS (Transport Layer Security) or parse SIP messages.

An Office Communications Server 2007 Enterprise pool consisting of more than one Front End Server requires a hardware load balancer. If you are deploying a Standard Edition Server or a single Enterprise Edition Front End Server, a load balancer is not required. A hardware load balancer is also required for arrays of Office Communications Server 2007 Edge Servers or an array of Standard Edition Servers configured as a Director. These requirements are summarized in the following table.

Table 76 Hardware load balancer requirements for Office Communications Server 2007

Note:
Office Communications Server 2007 does not support the use of Windows Server 2003 Network Load Balancer in any production deployments.