Brocade Virtual ADX Server Load Balancing Guide (Supporting ADX v03.1.00) - Manual (Page 126)

110 Brocade Virtual ADX Server Load Balancing Guide
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Miscellaneous options
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Limiting the maximum number of TCP SYN requests
You can limit the maximum number of TCP SYN requests per second per server. A TCP SYN request
is a packet a client sends requesting a TCP connection to the server.
To limit the maximum number of TCP SYN requests to 3500, enter the following command.
Virtual ADX(config)#server syn-limit 3500
Syntax: [no] server syn-limit max_requests
The max_requests variable is maximum number of TCP SYN requests per second per server. Enter
an integer from 1 to 65535. The default value is 65535.
Configuring the maximum connection rate for a real server
Connection Rate Control (CRC) specifies the maximum number of new TCP, UDP, or individual port
connections per second allowed on a real server.
It enables you to limit the connection rate to a real server for the following:
• All TCP traffic
• All UDP traffic
• Individual TCP or UDP ports
The Brocade Virtual ADX increments the connection counter for real server connections only after
the Brocade Virtual ADX selects a server for the connection. If the Brocade Virtual ADX cannot
serve a client request because a real server, cache, or firewall already has the maximum number of
connections for the current second for the requested port, the Brocade Virtual ADX tries another
server. If there are no servers available, the Brocade Virtual ADX sends a TCP RST to the client.
If you configure a limit for TCP or UDP and also for an individual application port, the Brocade
Virtual ADX uses the lower limit. For example, if you limit new TCP connections to a real server to
1000 per second and also limit new HTTP connections to 600 per second, the Brocade Virtual ADX
limits connections to TCP port HTTP to 600 per second.
NOTE
The Brocade Virtual ADX counts only the new connections that remain in effect at the end of the
one-second interval. If a connection is opened and terminated within the interval, the Brocade
Virtual ADX does not include the connection in the total for the server.
NOTE
Connection rates might not be strictly limited to the configured values. A slight drift can be
introduced due to latency. For example, with traffic running at 1000 connections per second, and
the max-tcp-conn-rate command is configured at 100, the connection rate could go up to 140.
To limit the number of new TCP and UDP connections a real server can receive each second, enter
commands such as the following.
Virtual ADX(config)#server real RS1 10.2.3.4
Virtual ADX(config-rs-RS1)#max-tcp-conn-rate 1000
Virtual ADX(config-rs-RS1)#max-udp-conn-rate 800