ClickArray Networks Inc.s Array 1000 appliance integrates several Web traffic acceleration components into one device saving smaller companies money as well as simplifying network management. However, for sites where a one-box system isnt a good fit—such as those that cannot afford a single point of failure in their Web infrastructures—other types of content accelerators, such as the line of devices from NetScaler Inc., offer a compelling alternative for maintaining and scaling an enterprise Web presence.
Armed with what the company calls Request Switching Technology, NetScalers accelerated traffic management appliances manage Internet connections between clients and the Web servers to ensure faster user response time, increase server productivity and cache efficiency, and protect against illegitimate traffic surges such as DoS (denial-of-service) attacks.
The Request Switching Technology maintains persistent or "keep alive" HTTP 1.1 connections between Web browsing clients and the Web servers. Web servers can allow persistent connections to speed Web page downloads and minimize latency because only a single connection is needed to load the contents of a page. Without persistent connections, clients must usually open several TCP connections to fetch all the objects in a Web page, creating more latency on the client and requiring the Web server to process additional connection request.
Most IT managers disable persistent connection on their Web servers to serve more clients and avoid idle connections. In addition, DoS attacks and other illegal traffic generators over these connections can quickly bring activity at a site to a screeching halt.
A NetScaler appliance sits in front of a companys Web server farm and maintains persistent connections while protecting the servers against surges and attacks. The appliance manages the traffic and allows persistent connections to the servers, which frees up server CPU cycles to handle other tasks.
The NetScaler appliance multiplexes multiple client connections—combining multiple signals or information streams into a single, complex signal and sending it over a single line—to a smaller number of persistent connections that the Web servers behind it can handle efficiently, thus increasing the overall performance of the Web site. IT managers can use the NetScaler appliance to scale the traffic a site can handle without upgrading or adding more Web servers.
Larger sites also employ caching appliances and content delivery network to minimize WAN latency by localizing content to the clients. This strategy works well for static content but because a large portion of the content in todays Web sites is dynamic, the cost of these systems might not justify the performance they provide.
For sites that employ caching solutions, NetScalers Request Switching Technology provides caching redirection, enabling noncacheable content to bypass the caching devices and be quickly redirected to the servers. By offloading noncacheable content, the NetScaler appliance optimizes cache hits and enables enterprises to more effectively use their caching devices.