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Web OS 10.0 Application Guide
4.
The California Web switch responds to the DNS request, listing the IP address with the
current best service.
Each switch with GSLB software is capable of responding to the client's name resolution
request. Since each switch regularly checks and communicates health and performance infor-
mation with its peers, either switch can determine which site(s) are best able to serve the cli-
ent's Web access needs. It can respond with a list of IP addresses for the Foo Corporation's
distributed sites, which are prioritized by performance, geography, and other criteria.
In this case, the California Web switch knows that Foo Corp. Denver currently provides better
service, and lists Foo Corp. Denver's virtual server IP address first when responding to the
DNS request.
5.
The client connects to Foo Corp. Denver for the best service.
The client's Web browser will use the IP address information obtained from the DNS request
to open a connection to the best available site. The IP addresses represent virtual servers at any
site, which are locally load balanced according to regular SLB configuration.
If the site serving the client HTTP content suddenly experiences a failure (no healthy real serv-
ers) or becomes overloaded with traffic (all real servers reach their maximum connection
limit), the switch issues an HTTP Redirect and transparently causes the client to connect to
another peer site.
The end result is that the client gets quick, reliable service with no latency and no special cli-
ent-side configuration.
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Chapter 12: Global Server Load Balancing
212777-A, February 2002
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