Brocade Virtual ADX Server Load Balancing Guide (Supporting ADX v03.1.00) - Manual (Page 182)

166 Brocade Virtual ADX Server Load Balancing Guide
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Layer 7 health checks
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• The Current Appl RTT field displays in microseconds the current application round trip time. If
this value exceeds the configured l7 response threshold, the port is brought down.
• The TCP RTT field is a smoothed l4 round trip time that is used by the response time predictor.
• The Appl RTT field is a smoothed l7 round trip time that is used by response time predictor.
Displaying health check related error messages
The server debug hc-error command, when enabled, displays health-check related error messages
to the console.
Syntax: server debug hc-error
Layer 7 health checks
For certain TCP and UDP application ports, the Brocade Virtual ADX can send application-specific
health checks to determine the health of the application. For example, the Brocade Virtual ADX can
send user-configurable HTTP requests to real servers to assess the health of the servers.
When you bind a real server to a virtual server using an application port that is known to the
Brocade Virtual ADX, the Brocade Virtual ADX sends a Layer 7 health check to the application on
the real server to bring up the application port.
By default, if a client requests a TCP/UDP port that is not available, the Brocade Virtual ADX does
not send an ICMP “Destination Unreachable” message to the client. For HTTP traffic, you can
configure the Brocade Virtual ADX to send such a message to the client by enabling the ICMP
Message feature for HTTP. Refer to
“Sending ICMP Port Unreachable or Destination Unreachable
messages” on page 113 for details.
You can enable a Layer 7 health check globally by configuring a port profile or locally by enabling
the health check on an individual real server. In addition, you can customize some types of Layer 7
health checks for individual real servers. For example, you can specify a URL that the Brocade
Virtual ADX should request on a specific real server when sending the Layer 7 HTTP health check to
that server.
The following Layer 7 health check types are supported:
• “DNS” on page 168
• “FTP” on page 169
• “HTTP (status code)” on page 169
• “HTTP (content verification)” on page 170
• “HTTP (status code)” on page 169
• “HTTP (content verification)” on page 170
• “Scripted (content verification for unknown ports)” on page 170
• “IMAP4” on page 171
• “LDAP” on page 171
• “MMS” on page 172
• “NNTP” on page 173
• “PNM” on page 173
• “POP3” on page 173