Nortel Networks WEB OS 212777 - Manual (Page 219)

212777-A, February 2002
219
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HAPTER
10
Health Checking
Content intelligent Web switches allow Web masters to customize server health checks to ver-
ify content accessibility in large Web sites. As the amount of content grows and information is
distributed across different server farms, flexible, customizable content health checks are criti-
cal to ensure end-to-end availability.
The following Web OS health-checking topics are described in this chapter.
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“Real Server Health Checks” on page 221 . This section explains the switch’s default
health check, which checks the status of each service on each real server every two
seconds.
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“DSR Health Checks” on page 222 . This section describes the servers’ ability to respond
to the client queries made to the Virtual server IP address when the server is in Direct
Server Return (DSR) mode.
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“Link Health Checks” on page 223 . This section describes how to perform Layer 1 health
checking on an Intrusion Detection Server (IDS).
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“TCP Health Checks” on page 224 . TCP health checks help verify the TCP applications
that cannot be scripted.
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“ICMP Health Checks” on page 224 . This section explains how ICMP health checks are
used for UDP services.
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“Script-Based Health Checks” on page 225 . This section describes how to configure the
switch to send a series of health-check requests to real servers or real server groups and
monitor the responses.
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Application-based health checks:
o “HTTP Health Checks” on page 231 . This section provides examples of HTTP-based
health checks using hostnames.
o “UDP-Based DNS Health Checks” on page 233 . This section explains the functional-
ity of the DNS Health Checks using UDP packets.