A hardware load balancer (HLB) is required for every Enterprise pool. The HLB is an important element of the redundancy story offered by Enterprise Edition. An Enterprise pool contains one or more front-end servers that perform the same function. Therefore, clients can connect to any of the available front-end servers. It is important that the client does not need to know which front-end server it should connect to. By using an HLB, clients connect to a single FQDN and the HLB determines which front-end server should service the request based on availability and workload. After a client's connection is routed by the HLB to a particular front-end server, the HLB must be capable of routing all traffic from that client to the same front-end server for the duration of the user's session.
At the time of writing, Microsoft has tested and supports Office Communications Server 2007 with the following HLBs (see the Additional Resources section at the end of this chapter for the link):
You must configure a static IP address for the virtual IP address (VIP) of the HLB. The HLB must be configured with the static IP address of each front-end server of the Enterprise pool to load balance. For details on how to configure the specific HLB of your choice, see the Partner Documentation section at http://office.microsoft.com/en-us/FX011526591033.aspx.
Finally, you must publish the FQDN of the Enterprise pool in DNS. An A(Host) record must be defined for the pool FQDN, and the IP address to match to this FQDN should be the IP address of the HLB's VIP.
Select Start, select Administrative Tools, and then select DNS. Right-click your domain's node under Forward Lookup Zones and select New Host (A), as shown in Figure 3-21. Enter the Enterprise pool's FQDN in the Name field of the New Host dialog box.
Verify that you configured the HLB with this IP address, and make sure you can resolve the pool's FQDN. You can easily do this by performing a ping command. Open a Command Prompt window, and type ping <pool fqdn>.
The pool's FQDN is automatically defined once you specify the pool name. It is composed of the name specified in the Pool Name field and the domain's name shown in the Domain field in the Create Enterprise Pool Wizard. This is shown in Figure 3-22.
The pool name can be any value you select, as long as it does not conflict with the name of an existing pool. The pool name gets populated as the common name (CN) of the pool object and the value of the msRTCSIP-PoolDisplayName attribute.
The SQL Server instance is parsed, and the server name portion is stored in the msRTCSIPBackEndServer attribute. By default, if no instance name is supplied, the instances created are called RTC, RTCDYN, and RTCCONFIG. It is recommended not to specify any instance name when creating a new pool. The RTC database contains user and pool information synchronized from Active Directory. The RTCDYN database stores transient information, such as subscriptions, endpoints, and publications. The RTCCONFIG database contains pool-level configuration settings specific to the Enterprise pool.