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How GSLB Works
GSLB is based on the Domain Name System (DNS) and proximity by source IP address. In the
example in
at "www.foocorp.com." The Foo Corporation has two Web sites: one in California, and one in
Denver, each with identical content and available services. Both Web sites have an Alteon Web
switch configured for GSLB. These switches are also configured as the Authoritative Name
Servers for "www.foocorp.com."
Foo Corp. California
Web
Servers
Figure 12-1 DNS Resolution with Global Server Load Balancing
The DNS resolution for GSLB is described in detail in the following procedure:
1.
The client Web browser requests the "www.foocorp.com" IP address from the local DNS.
2.
Client's DNS asks its upstream DNS, which in turn asks the next, and so on, until the
address is resolved.
Eventually, the request reaches an upstream DNS server that has the requested IP address
information on hand or the request reaches one of the Foo Corporation's DNS servers.
3.
The Foo Corporation's California DNS has been configured to use the local Web switch
with GSLB software as the authoritative name server for "www.foocorp.com."
212777-A, February 2002
Figure
12-1, a client is using a browser to view the Web site for the Foo Corporation
DNS
DNS
3
Web Switch
4
Switches regularly exchange performance information
DNS response
lists best site's
IP address first
Client Site
DNS
1
HTTP
Request
5
Request
2
Internet
Chapter 12: Global Server Load Balancing
Web OS 10.0 Application Guide
Foo Corp. Denver
DNS
Best Service!
Web Switch
Web
Servers
n
291
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