Primer: Application Switching

Keith Ferrell

Jun. 02, 2003
1 min read

What is it? A way of handling network traffic by identifying and analyzing packets of information before they reach the server. Also known as content switching, application switching can identify legitimate requests, deny attacks and, in some cases, rank traffic by priority. A financial transaction or important database query, for example, might be given priority over a page-surf.

How does it work? The International Organization for Standardization’s (ISO) model divides networks into seven layers, each handling a specific aspect of network communications. Layer 1 is where physical operations take place. Layer 4 handles data connections and transfers between clients and servers; the protocols here examine the header messages of requests to learn how to steer the requests to the right server. Applications directly involving the user are executed at Layer 7.

Switches act as guides for the different layers, which have evolved to reflect the increasingly sophisticated ways in which networks are being used. The typical Layer 7 application switch sits between the user’s network and the server from which the user is requesting information. The switch reviews and analyzes incoming information packets in order to block false requests, guide legitimate requests to servers and prioritize traffic. These switches may also compress and encrypt data, thus ensuring security and privacy.

What’s the business benefit? A network that’s faster, more secure, and easier and cheaper to manage. Layer 7 switches can analyze more of the information that accompanies a packet of data—such as the type of device or application that sent the packet—than can switches based on lower layers. Because of this, these switches are able to follow more-complicated business rules. An application switch also conducts more checks on requests before they reach the server; it can catch a greater number of false requests and lighten the load the server bears. Those checks also look for signs of security breaches or attacks.

With fewer requests to process and less likelihood of an attack, server administration becomes simpler. And, of course, users notice an improvement because application switches are better able to handle traffic surges and usage spikes than their predecessors.

Doesn’t my network already do these things? Perhaps, but probably not well. The explosion in Web-based applications prompted many vendors and network managers to graft new functions onto the infrastructure at Layer 4 and lower. But those layers are ill- prepared to examine packet information deeply or to make complicated decisions. Accelerator cards and the like promise higher speeds but still fail to make use of all the information available at Layer 7. Earlier approaches also have trouble sorting out the flurry of requests in a traffic surge, and managing the add-ons makes administering the network more difficult.

Who’s using it? High-traffic Web sites such as MSN, Yahoo and eBay, along with telecommunications firms such as NTT, are the first to put the switches to work. Established application-switch vendors—including Cisco, NetScaler, Redline, Nortel, Radware, and F5—are offering products ready to install from the low $20,000s to the upper $70,000s.