Network load balancing (NLB) distributes traffic between multiple hosts based on each host's current load. Each new client is directed to the host under the least load. It is also possible to configure NLB to send traffic proportionally to hosts within the cluster. For example, in a cluster with four hosts, you could configure an NLB cluster to send 40 percent of incoming traffic to one host and split the remaining 60 percent across the other three hosts. All editions of Windows Server 2008 support NLB.
You can add and remove nodes to NLB clusters easily by using the Network Load Balancing Manager console, shown in Figure 16-3. NLB clusters reconfigure themselves automatically when you add a new node or remove a node or a node in the cluster fails. Each node in an NLB cluster sends a message to all other nodes after a second, informing them of its status. The term for this message is heartbeat. When a node fails to transmit five consecutive heartbeat messages, the other nodes in the cluster alter the configuration of the cluster, excluding the failed node. The term for the reconfiguration process is convergence. Convergence also occurs when the heartbeat of a previously absent node is again detected by other nodes in the cluster. You can take an existing node in an NLB cluster offline for maintenance and then return it to service without having to reconfigure the cluster manually because the removal and addition process occurs automatically.
ÄJj Network Load Balancing Manager
File Cluster Host Options Help
Network Load Balancing Clusters B fk} (10,0,0,111)
E3 WELLINGTON(Local Area Connf § WANGARATTA(Local Area Conr
Port lules configured on WELLINGTON (Local Area Connection 2) Cluster IP ad... | Status | Start_| End_| Protocol
I Mode_I Priority
0004 12/6/2008 8:04:59 PM Loadingconfiguration information from host "WELLINGTON. contoso .interns
0005 12/6/2008 8:04:59 PM Loadingconfiguration information from host "WANG AR ATTA. contoso. interr
0006 12/6/2008 8:05:06PM 10,0,0,200 WELLINGTON Begin configuration change
0007 12/6/2008 8:05:06PM 10,0,0,200 WELLINGTON Waiting for pending operation 4
0008 12/6/2008 8:05:23PM 10,0,0,200 WELLINGTON Update 4 succeeded [double click for details,,,]
0009 12/6/2008 8:05:23PM 10,0,0,200 WELLINGTON End configuration change
0010 12/6/2008 8:06:27PM 10,0,0,111 WELLINGTON Begin configuration change
0011 12/6/2008 8:06:27PM 10,0,0,111 WELLINGTON Waiting for pending operation 5
0012 12/6/2008 8:06:47PM 10,0,0,111 WELLINGTON Update 5 succeeded [double click for details,,,]
0013 12/6/2008 8:06:47PM 10,0,0,111 WELLINGTON End configuration change
0014 12/6/2008 8:07:52PM 10,0,0,111 WANG AR ATTA Begin configuration change
0015 12/6/2008 8:07:52PM 10,0,0,111 WANG AR ATTA Waiting for pending operation 2
0016 12/6/2008 8:08:17 PM 10,0,0,111 WANG AR ATTA Update 2 succeeded [double click for details,,,]
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