
Chapter 4: Configuring the High-Level Network
4-6
Round Robin
This is the default load balancing mode. Round Robin mode passes each
new connection request to the next server in line, eventually distributing
connections evenly across the array of machines being load balanced.
Round Robin mode works well in most configurations, especially if the
equipment that you are load balancing is roughly equal in processing speed
and memory.
Ratio
BIG-IP distributes connections among machines according to ratio weights
that you define, where the number of connections that each machine
receives over time is proportionate to a ratio weight you define for each
machine. This is a static load balancing mode, basing distribution on static
user-assigned ratio weights that are proportional to the capacity of the
servers.
Load balancing calculations may be localized to each pool (member-based
calculation) or they may apply to all pools of which a server is a member
(node-based calculation). Member-based calculation is specified by the
extension ratio_member. This distinction is especially important; in Ratio
Member mode, the actual ratio weight is a member attribute in the pool
definition, whereas in Ratio mode, the ratio weight is an attribute of the
node.
Dynamic ratio
Dynamic Ratio mode is like Ratio mode except that ratio weights are based
on continuous monitoring of the servers and are therefore continually
changing.
This is a dynamic load balancing mode, distributing connections based on
various aspects of real-time server performance analysis, such as the current
number of connections per node or the fastest node response time.
Dynamic Ratio mode is used specifically for configuring RealNetworks
RealServer platforms, Windows platforms equipped with Windows
Management Instrumentation (WMI), or any server equipped with an SNMP
agent such as the UC Davis SNMP agent or Windows 2000 Server SNMP
agent. To install and configure the necessary server software for these
systems, refer to Configuring servers and the BIG-IP for Dynamic Ratio
load balancing, on page 4-10.
Fastest
Fastest mode passes a new connection based on the fastest response of all
currently active nodes. Fastest mode may be particularly useful in
environments where nodes are distributed across different logical networks.
Load balancing calculations may be localized to each pool (member-based
calculation) or they may apply to all pools of which a server is a member
(node-based calculation). The variant of the mode using member-based
calculation is distinguished by the extension fastest_member.
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