Selecting A Load Balancing Metric; Weighted Firewalls; Health Check - Avaya P333R-LB Installation And Configuration Manual

Chapter 14 Load Balancing in the P333R-LB
restored to its original configuration. As a result, persistency is only partially
recovered, making MinMiss Hash a non-predictable metric.

Selecting a Load Balancing Metric

The different metrics available allow you to select the metric that best matches your
network topology.
The Hash metric produces predictable forwarding decisions. Therefore, this is the
only metric appropriate for configurations that involve load balancers on both sides
of the firewalls (for example, Transparent Routing FWLB, and Bridging FWLB).
Furthermore, loss of persistency may not be an issue where a state-synchronizing
firewall cluster is deployed.
For Transparent Routing FWLB, to ensure mapping of the same session to the same
firewall by both load balancers, the default hash key is a combination of the source
and destination IP addresses.
The MinMiss Hash metric maintains persistency better than the Hash metric. When
there is not need to maintain consistency between load balancers (for example, Non
Transparent FWLB), this metric should be used.

Weighted Firewalls

You can assign weights to firewalls to enable faster firewalls to receive a larger
share of sessions. This minimizes overloading and maximizes functionality.
If you assign a weight to a firewall, the sessions are distributed to the firewalls in the
same metric chosen (Hash or MinMiss Hash). However, weighted firewalls are
assigned a larger share of sessions. For example, if you assign a weight of 10 to one
firewall (the default value), and assign a weight of 20 to a second firewall, the
second firewall receives 2 sessions for each session directed to the first firewall.

Health Check

The P333R-LB constantly health checks the firewall paths to ensure that each
firewall is accessible and operational. A firewall that fails the health check is
automatically removed from the load balancer's internal list of currently available
firewalls.
The P333R-LB uses the ICMP Echo health-check method. Each load balancer
periodically pings the Real Server and checks if an answer was received.
For FWLB, the health check must is performed beyond the firewalls as well in order
to check the entire data path. In order to insure that the health check packets
traverse the same firewall in both directions, the Health Check IP addresses (the
packet's source and destination IP addresses) are the interfaces of the load balancer
on each side of the firewall. For each load balancing interface, the local and remote
addresses should be configured. The load balancers on both sides of the firewalls
must be configured symmetrically. For information on configuration, see the
Avaya P333R-LB User's Guide 15