Citrix NetScaler EE, Руководство по установке и настройке

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Selecting a Load Balancing Method
Aug 14, 2013
By default, the SD-WAN 4000/5100 Provisioning Wizard sets up load balancing to handle different kinds of connections
appropriately. This default behavior is adequate for most installations.
Sending all the connections from the same remote accelerator to the same local accelerator maximizes the benefits of SD-
WAN compression, and the default load balancing method accomplishes this. If an instance becomes overloaded or
unavailable, new connections are reallocated.
By default, the NetScaler instance uses the least-connection method to balance the load across the accelerators. This
method applies whether or not the connections are accelerated. Connections are persistent, but persistency is
discontinued for an instance that becomes overloaded, and is lost if the local appliance is restarted or when no traffic from
a remote appliance is seen for more than 24 hours.
For incoming accelerated connections (that is, connections with SD-WAN options in the header of the SYN packet), all
connections from a given remote SD-WAN are sent to the same local accelerator.
The identity of the remote SD-WAN is determined by one of the SD-WAN SYN options: the "AgentID" field, which contains
the management IP address of the remote SD-WAN.
This method is used for connections from remote SD-WAN appliances and remote SD-WAN Plug-ins.
Incoming non-accelerated connections and all outgoing connections are also distributed among the accelerators according
to the least-connection method, but since they do not contain an AgentID field, they cannot use AgentID persistence.
Instead, they use SRCIPDESTIP persistence, meaning that connections with the same IP addresses use the same
accelerator.
If an instance is overloaded, the NetScaler instance bypasses it for new connections, sending them through without
acceleration. Existing connections continue to be sent to the instance.
This behavior is controlled by the skipPersistency parameter. The default behavior is -skippersistency ReLB. The alternative
behavior, -skippersistency bypass, instructs the NetScaler instance to pass the connection through without sending it to an
accelerator.
The default load balancing behavior is adequate for most installations, but sometimes customization is needed. This is most
commonly true when a few remote sites have much more traffic than the rest. In that case, it can be worthwhile to assign
these large sites to accelerators explicitly.
Optional load balancing behavior includes the use of static routing (for hand-crafted load balancing) and variations on the
least-connection with AgentID and SRCIPDESTIP persistence methods used in the default configuration. The behavior for