The All-New Switch Book: The Complete Guide to LAN Switching Technology, Second Edition

4.5. A Switch Is a Switch Is a Switch Except When ...

A switch is a switch is a switch except when it is not a switch (at least in the traditional Layer 2 switching environment). So far, we really have covered the basics of switching from a LAN perspective, but it is important to mention the so-called Layer 4-7 switching that many are deploying in their networks.

Many vendors have started marketing equipment that performs Layer 4-7 functions as a Layer 4-7 switch. In the case of the Layer 4-7 switch, you are not really seeing a switch, and multiple vendors use the definition loosely so it may not really be exactly the same between vendors. You might come across some terms to describe the Layer 4-7 switching that use the word "switch" but that do not perform a switching function are Layer 4-7 switch, web switch, application switch, and content switch. Heck, there was even a VPN switch there for a little while.

The phrase "Layer 4-7 switching" is a term that is usually misrepresented. Several vendors market the Layer 4-7 switch, but don't always define it in the same manner. In Chapter 3, we discussed Layer 4 switching and how that term relates to MultiLayer Switching. In the Layer 4-7 Switching category, Layer 4 services are used to assist in balancing data destined for servers within a network.

Refer back to section 1.1.4 of this book. Layer 4 switches operate at the TCP/UDP level and will make decisions about where to send traffic based on information that is stored at the transport ...