Coyote Point Systems Equalizer Spezifikationen PDF herunterladen (Seite 373)

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Enabling/Disabling L4 UDP Probes

UDP probes are enabled for a UDP server as soon as a server instance for the server is added to a server pool.

Default settings for probe parameters are used unless specifically set on the server pool.

L4 TCP/IP Probes

L4 TCP probes (acvd) are performed on servers running TCP protocol only. Equalizer attempts to open a TCP

connection with a server on its configured IP address and probe port. A TCP probe is successful if the connection

is established.

Enabling/Disabling L4 TCP Probes

TCP probes are enabled for a TCP server as soon as a server instance for the server is added to a server pool.

Default settings for probe parameters are used unless specifically set on the server pool.

Active Content Verification (ACV) Probes

Active Content Verification serves two purposes: L4 probing and L7 probing. It is a mechanism for checking the

validity of a server pool. When you enable ACV for a server pool, Equalizer requests data from each server pool in

a cluster and verifies that the returned data contains a character string that indicates that the data is valid. You can

use ACV with most network services that support a text-based request/response protocol, such as HTTP.

Note - You cannot use ACV with Layer 4 UDP clusters.

ACV checking requires that the server instance is configured with L4 probing (probe_l4) on. This is the default

server instance configuration. To enable ACV, an ACV response string is configured for a server pool.The ACV

probe is limited to 99 characters, and must use only the printable ASCII characters (decimal 32 to 126). Equalizer

then searches for the ACV response string in the first 1024 characters of the server’s response to high-level TCP

probes. If the ACV response string is not found, the server is marked “DOWN”. An ACV query string can be

specified if the service running on the server’s probe port requires input in order to respond. If the TCP probe

connection is not established ACV probing will fail as well.

ACV is best explained using a simple example. HTTP protocol enables you to establish a connection to a server,

request a file, and read the result. The example below shows the connection process when a user requests a telnet

connection to an HTTP server and requests an HTML page.

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Equalizer Administration Guide

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