Brocade Communications Systems ServerIron ADX 12.4.00 User Manual
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ServerIron ADX Global Server Load Balancing Guide
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Configuring GSLB protocol parameters
1
Syntax: [no] round-trip-time cache-interval
The
11-1/2 days). The default is 120 seconds.
Changing the RTT cache prefix
You can change the RTT cache prefix, which specifies the level of aggregation that occurs in the
GSLB ServerIron ADX’s RTT cache.
The entries in the RTT cache include IP address information for the clients. To avoid overflowing the
cache, cache entries are aggregated based on the IP information. For example, if the GSLB
ServerIron ADX receives RTT information for clients at 192.21.4.69 and 192.21.4.18, and the
cache prefix is 31 bits, both addresses go in as separate entries. However, if the prefix is 16 bits,
the GSLB ServerIron ADX aggregates the addresses. In this case, only one entry, 192.21.x.x goes in
the cache.
To change the RTT cache prefix from 20 bits to 16 bits, enter commands such as the following:
ServerIronADX(config)# gslb policy
ServerIronADX(config-gslb-policy)# round-trip-time cache-prefix 16
Syntax: [no] round-trip-time cache-prefix
The
The default is 20.
Changing the RTT tolerance
To change the RTT tolerance from 10% to 70%, enter commands such as the following:
ServerIronADX(config)# gslb policy
ServerIronADX(config-gslb-policy)# round-trip-time tolerance 70
Syntax: [no] round-trip-time tolerance
The
the GSLB ServerIron ADX to favor one site over the other based on the RTT. You can specify a value
from 0-100. The default is 10%.
Change the RTT explore percentage
You can change the RTT explore percentage, which prevents the GSLB ServerIron ADX from unfairly
biasing selection of the best site based on previous RTT responses.
Site ServerIron ADXs send RTT information only for the sessions that clients open with them. These
are clients referred to the site ServerIron ADX by the GSLB ServerIron ADX. If the metrics that come
before this one (based on the GSLB policy order) do not select a “best” site, the ServerIron ADX
selects a site based on RTT.
Since the only RTT information received by the GSLB ServerIron ADX comes from the site ServerIron
ADXs to which the GSLB ServerIron ADX has referred clients, it is possible for the GSLB ServerIron
ADX to continually bias its selection toward the first site ServerIron ADX that sent RTT information.
To prevent this from occurring, the GSLB ServerIron ADX intentionally ignores the RTT metric for a
specified percentage of the requests from a given client network. You can specify an RTT explore
percentage from 0-100. The default is 5. By default, the GSLB ServerIron ADX ignores the RTT for
5% of the client requests from a given network.
To change the RTT explore percentage, enter commands such as the following: