Coyote Point Systems Equalizer, Installation And Administration Manual

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Chapter 1:Overview
8 Equalizer Installation and Administration Guide
3. The authoritative name server delegates the query to the Equalizer servers at each of
the sites in the geographic cluster. (Step 3 in Figure 3.) If the site that’s queried doesn’t
respond, the client’s name server tries one of the others. (In Figure 3 and Figure 4, site
2 is handling the name resolution request.)
Figure 3 Sending name resolution requests to servers in a geographic cluster
Equalizer then performs a number of steps to determine which site in the geographic
cluster should handle the request:
1. First, Equalizer identifies the geographic cluster that has been configured with the
requested domain name, in this case
www.coyotepoint.com
.
2. Once the geographic cluster has been identified, Equalizer sends geographic query
protocol probes to the agents running at each site in the cluster. (Step 1 in Figure 4.)
These probes contain information about the client that made the request and the
resource that is being resolved. The site handling the resolution request (site 2 in
Figure 4) also queries its local agent.
3. When an agent receives a probe request, it performs two actions:
a. First, the agent checks the availability of the requested resource. If the resource is
unavailable at the agent's site, the agent responds to the server with an error
indication. (Step 2 in Figure 4.)
b. If the resource is available and ICMP triangulation is enabled, the agent sends an
ICMP echo request (ping) to the client that initiated the request. When the echo
reply arrives, the agent forwards the latency information to the server that sent the
geographic probe. (Step 2 in Figure 4.)
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