DistributedDirector
The DistributedDirector, provided by the hosting data center,
routes a user to the most appropriate data center, based on
logical proximity and the response times of the data center.
In the Networking Academy implementation, Cable and Wireless
Internet Services uses a Cisco DistributedDirector in the
San Jose data center. Additional DistributedDirectors will
be placed in different locations around the world as the network
demand increases. DistributedDirector looks at the availability
and timing of the Web servers and routes traffic to the closest
Web server, based on pre-configured decisions.
LocalDirector
Load balancing devices, like the Cisco LocalDirector, allow
for Web server redundancy. LocalDirectors are configured to
know how many Web servers there are so they can balance the
loads among busy and less active servers by checking the frequency
of their responses. If a Web server goes down, the LocalDirector
routes traffic to other Web servers that are fully functional.
The LocalDirector frequently checks the status of the Web
servers and will stop directing traffic to a non-responding
Web server without any manual intervention.
The Networking Academy implementation uses two Cisco LocalDirectors
per data center, one primary and one secondary. A failover
cable set up between the two LocalDirectors facilitates communication
between them. If one of the LocalDirectors fails to respond,
the active LocalDirector takes over.
|
