Amer Networks E5Web GUI - Manual (Page 689)

10.4.3. Selecting Stickiness
In some scenarios, such as with SSL connections, it is important that the same server is used for a
series of connections from the same client. This is achieved by selecting the appropriate
stickiness option and this can be used with either the round-robin or connection-rate algorithms.
The stickiness options are as follows:
Per-state Distribution This mode is the default and means that no stickiness is
applied.
Every new connection is considered to be
independent from other connections even if they come from
the same IP address or network. Consecutive connections from
the same client may therefore be passed to different servers.
This may not be acceptable if the same server must be used for
a series of connections coming from the same client. If this is
the case then stickiness is required.
IP Address Stickiness In this mode, a series of connections from a specific client will
be handled by the same server. This is particularly important
for TLS or SSL based services such as HTTPS, which require a
repeated connection to the same host.
Network Stickiness This mode is similar to IP stickiness except that the stickiness
can be associated with a network instead of a single IP
address. The network is specified by stating its size as a
parameter.
For example, if the network size is specified as 24 (the default)
then an IP address 10.01.01.02 will be assumed to belong to
the network 10.01.01.00/24 and this will be the network for
which stickiness is applied.
Stickiness Parameters
If either IP stickiness or network stickiness is enabled then the following stickiness parameters
can be adjusted:
• Idle Timeout
When a connection is made, the source IP address for the connection is remembered in a
table. Each table entry is referred to as a slot. After it is create, the entry is only considered
valid for the number of seconds specified by the Idle Timeout. When new connection is made,
the table is searched for the same source IP, providing that the table entry has not exceeded
its timeout. When a match is found, then stickiness ensures that the new connection goes to
the same server as previous connections from the same source IP.
The default value for this setting is 10 seconds.
• Max Slots
This parameter specifies how many slots exist in the stickiness table. When the table fills up
then the oldest entry is discarded to make way for a new entry even though it may be still
valid (the Idle Timeout has not been exceeded).
The consequence of a full table can be that stickiness will be lost for any discarded source IP
addresses. The administrator should therefore try to ensure that the Max Slots parameter is
set to a value that can accommodate the expected number of connections that require
stickiness.
Chapter 10: Traffic Management
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