ADCs Take Over Where Server Load Balancers Leave Off
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Overview: Application delivery controllers evolved from load balancers. Beyond addressing scalability and availability problems, an ADC understands applications, and optimizes server performance, offloading compute-intensive tasks that swamp CPUs, slowing the server’s ability to quickly deliver applications.
In the last decade, server load balancers were hailed as the solution to website scalability and availability problems. These devices balanced traffic across servers to ensure the site was available and could handle traffic spikes. If one server went down, the load balancer redirected traffic. When a site got "slashdotted" you could add more servers transparently.
Flash forward to 2010… Web servers aren't just delivering static content, they're delivering applications. Businesses are using web-based applications to deliver mission-critical functionalities to employees and customers. Simple load balancing is no longer sufficient. Fortunately, load balancers have evolved into Application Delivery Controllers. This new species understands application specific traffic, and can optimize application server performance by offloading many of the compute-intensive tasks that would otherwise bog down CPUs, thus, slowing down the server’s ability to quickly deliver applications.
While, incredibly valuable to the data center, server load balancers lack the advanced application-aware functions that today’s data centers require. For example, they are unable to support persistent sessions based on cookies and HTTP headers; they lack application layer routing capabilities; they are unable to perform TCP and HTTP protocol connection management; and they can become a performance bottleneck when they multitask the many server offloading and acceleration functions.
Today’s advanced application delivery controllers have evolved from server load balancers. This white paper discusses how Application Delivery Controllers have taken over where load balancers left off.