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Many IT organizations have deployed application delivery controller technology in an effort to improve application performance. Application delivery controllers (ADCs) improve application performance by sitting in front of a server farm and delivering service requests to the members of the server farm based on criteria such as the load that each server is currently processing.
Application delivery controller technology and virtualization
Increasingly, ADCs are playing a role in server virtualization. One of the primary benefits of server virtualization technology is agility. Once a server has been virtualized, it is possible to dynamically provision virtual machines (VMs) and to dynamically move VMs among physical servers, both within a given data center and between disparate data centers without service interruption. Unfortunately, while it is possible to move a VM between physical servers in a matter of seconds or minutes, it can take days to move or reconfigure the supporting infrastructure.
IT organizations will not realize the full value of server virtualization until all of the components of the infrastructure that support a VM can be moved or reconfigured to support the VM once it is moved. Then, the process takes no more than a few minutes. That will mean virtualizing ADCs and using them in the delivery of applications from virtual servers.
Read more about the role of application delivery controller technology in virtualization.
Application delivery controllers and advanced functionality
An ADC can also accelerate the performance of applications delivered over the wide area network (WAN) by implementing optimization techniques such as compression and reverse caching. The basic role of compression is to reduce the amount of traffic transmitted over the WAN. With reverse caching, new user requests for static or dynamic Web objects can often be delivered from a cache in the ADC rather than having to be regenerated by the servers.
Read more about application delivery and the WAN.
Another way that an ADC improves application performance is by performing computationally intensive tasks -- such as SSL or TCP processing -- by freeing up server resources.
In addition to that basic set of functions, some ADCs perform advanced functionality such as scripting, which allows the IT organization to directly classify and modify the traffic of any IP-based application. Other advanced functionalities that some ADCs provide include application response time monitoring and security functionality such as application layer firewalls.
Application delivery controller technology selection considerations
When selecting an ADC, IT organizations need to evaluate how well it provides the functionality described above and how well it performs in the environment in which it will be deployed. In addition, IT organizations often have to balance goals that are in conflict. For example, IT organizations must ensure that the ADC can provide all of the functionality that is currently needed at the lowest possible cost.
IT organizations also need to ensure that the application delivery controller technology will provide the performance that is currently needed even when a feature such as security is enabled. IT shops also have to take into account anticipated future demands in order to ensure that the ADCs that they acquire today don’t quickly become obsolete, either because they don’t offer the functionality that the organization will need in the future or they can’t provide the additional performance that will be required.
Read about virtual application delivery controller technology in the second part of this series.