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Chapter 14 Load Balancing in the P333R-LB
26 Avaya P333R-LB User’s Guide
Server Load Balancing
This section provides information on Server Load Balancing (SLB) implementation
of the P333R-LB, and includes configuration examples.
SLB replaces a single physical server with a group of servers that appear to the
clients as a single Virtual Server.
Benefits
SLB improves your network performance by:
• Minimizing server response time.
• Maximizing server availability.
• Increasing reliability - If any server fails, the remaining servers continue to
provide services seamlessly.
• Increasing scalability - Server configuration (removal/addition) can be
performed without disrupting the network.
How it Works
The P333R-LB balances the traffic among several servers which all have access to
identical applications and data. This involves intercepting all traffic between clients
and load-balanced servers and dynamically distributing the load according to
configured schemes called metrics. For more information on metrics, refer to Load
Balancing Metrics on page 37.
To intercept traffic to the servers, the P333R-LB presents itself to the clients as a
Virtual Server with a Virtual IP address (VIP). Client traffic travels to the P333R-LB
acting as a Virtual Server. The P333R-LB redirects this traffic using Network
Address Translation (NAT) to the available Real (balanced) Servers. Traffic from the
Real Servers back to the clients may return via the P333R-LB, depending on the load
balancing redirection method.
To maintain awareness of any changes in the Real Servers' availability, the
P333R-LB implements a Health Check mechanism to monitor the status of the Real
Servers. For more information, see Health Check on page 40.
P333R-LB enables the following methods of NAT, described in the following
sections:
• Half NAT - P333R-LB translates the VIP to the IP address of the Real Servers.
• Full NAT - P333R-LB translates client’s IP addresses to Proxy IP addresses, as
well as the VIP to the IP address of the Real Servers.
Half NAT Load Balancing
In Half NAT based load balancing, the P333R-LB replaces the Virtual IP address of
the P333R-LB with the real IP address of the Real Server. Responses made by the
Real Server must pass through the P333R-LB, where the Real Server IP is replaced