Definition: Web switch

A network device that routes traffic to the appropriate Web server based on the content of the packet. Also known as a "URL switch," "Web content switch," "content switch," "layer 7 switch" and "layer 4-7 switch," the Web switch is designed to provide improved load balancing for a website, because different requests can be routed to the servers configured to handle them.

For example, streaming audio and video have long-lived "sticky" connections and may be better served from a dedicated server or one that is closer to the user. Requests for static data can be directed to cache servers, while dynamic requests bypass the cache server.

Layer 7 Digs Deeper
The Web switch examines layer 4 and layer 7 in the network packet. Although any layer 4 switch can examine the TCP/IP port number and differentiate HTTP traffic (Web traffic) from the rest, the Web switch also inspects layer 7, which contains the details of the HTTP request. For example, an HTTP request for a static image would be directed to a cache server, while an HTTP request for a search would go to the Web server handling ad hoc queries. See well-known port, Content Smart Web Switch and TCP splicing.

 TCP/IP SWITCHING/ROUTING DECISIONS

  Layer and      Forwarding
  Protocol       Decision
  Inspected      Based on

  2 - Ethernet   MAC address

  3 - IP         Network address
  3 - IP         Service quality

  4 - TCP/UDP    Traffic type
      socket     (HTTP, FTP, etc.)

  7 - HTTP       HTTP request type

The First Web Switches

ArrowPoint Communications pioneered Web switching in 1998 with its Content Smart switch. The CS-100 (left) supported 16 Fast Ethernet ports, while the CS-800 (right) supported 32 Gigabit Ethernet ports. (Image courtesy of Cisco Systems, Inc.)