Changing Network Load Balancing Resource Limits in the Registry

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You can tune Network Load Balancing performance by manually modifying the following entries in the registry in the HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\WLBS\Parameters subkey.

  • AliveMsgPeriod
    Determines the period (in milliseconds) between Network Load Balancing heartbeat messages broadcast by each host.
    Default value: 1000 (one second)
    Possible range: 100–10000

  • AliveMsgTolerance
    Determines the number of AliveMsgPeriod periods to wait after the last message from a host before the host is declared offline and the cluster performs convergence.
    Default value: 5
    Possible range: 5–100

  • DescriptorsPerAlloc
    Determines the number of connection descriptors allocated at a time. Connection descriptors are used to track TCP connections.
    Default value: 512
    Possible range: 16–1024

  • MaxDescriptorAllocs
    Determines the maximum number of times that connection descriptors can be allocated (this value limits the maximum memory footprint of Network Load Balancing).
    Default value: 512
    Possible range: 1–1024

  • NumActions
    An internal Network Load Balancing entry. Increase the value of this entry only if you encounter an event log message that advises you to do so.
    Default value: 50
    Possible range: 5–500

  • NumPackets
    An internal Network Load Balancing entry. Increase the value of this entry only if you encounter an event log message that advises you to do so.
    Default value: 100
    Possible range: 5–500

  • NumAliveMsgs
    An internal Network Load Balancing entry. Increase the value of this entry only if you encounter an event log message that advises you to do so.
    Default value: 10
    Possible range: 5–500

  • MaskSourceMAC
    Enables masking of the Source media access control address.
    If the host is connected to a switch when Network Load Balancing is running in unicast mode, set the value of MaskSourceMAC to 1 (the default). If the Network Load Balancing host is running in unicast mode and is attached to a hub that is connected to a switch, set the value of this entry to 0. If Network Load Balancing is running in multicast mode, this setting has no effect.
    Default value: 1
    Possible range: 0–1

  • RemoteControlUDPPort
    Determines the UDP port that is used by Network Load Balancing to receive remote control messages. Note that for backwards compatibility, Network Load Balancing (and, on Windows NT 4.0, Windows Load Balancing Service) automatically listens to port 1717. If you decide to firewall port 2504 to block remote control messages, you also need to firewall port 1717.
    Default value: 2504

  • NetmonAliveMsgs
    Determines whether Network Monitor (NetMon) captures Network Load Balancing heartbeat messages on the local host.
    To allow NetMon to capture Network Load Balancing heartbeat messages on the local host, set the value of this entry to 1. To get the best performance, leave the value of this entry at its default value of 0.