Chapter 14 Load Balancing in the P333R-LB
40 Avaya P333R-LB User’s Guide
Weighted Real Servers
You can assign weights to Real Servers to enable faster servers to receive a larger
share of sessions. This minimizes overloading and maximizes functionality
If you assign a weight to a Real Server, the sessions are distributed to the servers in
the same metric chosen (Hash or MinMiss Hash). However, weighted servers are
assigned a larger share of sessions. For example, if you assign a weight of 100 to one
and do not assign a weight to a second server, the weighted server receives 10
sessions for each session directed to the second server. This is because the default
value of the server’s weight is 10.
Health Check
The P333R-LB constantly health-checks the Real Servers to ensure that each Real
Server (in this case, each server) is accessible and operational. A server that fails the
health check is automatically removed from the load balancer’s internal list of
currently available servers.
P333R-LB supports the following health-check methods:
•ICMP Echo - Each server is periodically pinged and checked if an answer was
received.
•TCP Port Checking - A TCP connection is periodically opened to every server,
checking for successful completion of the connection.
•HTTP Server Checking - Useful for web applications, this method enables
verifying HTTP server functioning by comparing the response from the server
with a complete sample of the web page. The P333R-LB sends a request to the
HTTP server to simulate an outside request. The P333R-LB compares the
server’s response with the sample to ascertain the level that the HTTP server is
functioning. P333R-LB supports the following HTTP retrieving methods:
—Head - Retrieve only the HTTP headers without document body content.
This is the default method.
—Get - Retrieve all data from the HTTP server.
P333R-LB supports the following responses:
—Any response - P333R-LB assumes the server is functional when P333R-LB
receives any response.
—Any OK response - P333R-LB assumes the server is functional when the
server’s response is one of the HTTP OK responses (codes 201-204).
—Exact OK response - P333R-LB assumes the server is functional only when
P333R-LB receives the exact response expected (code 200). This is the
default method.
You can configure the following parameters:
— The port to access - if you do not configure a port, the default is in the
following order: the Virtual Service Real port, Virtual port, or port 80.
— HTTP Request type - GET or HEAD (default HEAD)
— HTTP version 1.0 or 1.1 (default 1.0)