Ethernet switches, also known as bridges, are basic building blocks of networks, and are so commonly used that you may not give them a second thought. It’s possible to build networks without knowing very much about how switches work. However, when you build larger network systems, it helps to understand both what goes on inside a switch and how the standards make it possible for switches to work together.

Ethernet is used to build networks from small to large, and from simple to complex. Ethernet connects your home computers and other household devices; switches for home networks are typically small, low cost, and simple. Ethernet also connects the Internet worldwide, and switches for Internet Service Providers are large, high cost, and complex.

Campus and enterprise networks often use a mix of switches: simpler and lower-cost switches are usually found inside wiring closets and used to connect devices on a given floor of a building; larger and higher-cost switches are found in the core of the network and are used to connect all the building switches together into a larger network system. Data center networks have their own special requirements, and typically include high performance switches that can be connected in ways that provide highly resilient networks.

According to industry estimates, the worldwide market for enterprise switches recorded revenues of over $5 billion per quarter in 2012, with total revenues exceeding $20 billion for the year. For the second quarter of 2012, there were 55 million Gigabit Ethernet ports shipped, and 3 million 10-Gigabit ports. At that rate, over 230 million enterprise switch ports were sold in 2012. Aside from the enterprise market, there were annual revenues of roughly $14 billion for service provider switches, resulting in total Ethernet switch revenues of roughly $34 billion for 2012. To satisfy the large and ever-increasing market for Ethernet switches, there are many varieties of switches offered at many price points.

The many kinds of switches and the many features that can be found in those switches are both very extensive topics. Covering the entire range of technology and the various ways switches can be used in network designs would require an entire book, or even several books. Instead, we will provide an introduction and a brief tutorial on how switches function, as well as how they are used in network designs. We will also provide an overview of the most important features found in switches—from the basics, to the more advanced features found in higher-cost and specialized switches.

Figure 1 shows the topics discussed in this guide. Chapter 1 provides a tutorial on basic switch operation and the spanning tree protocol. In Chapter 2, we look at the management of switches, and at some of the most widely used switch features. Chapter 3 describes the advantages of switches in network designs, and how implementing a hierarchical network design can help maintain stable operations. Chapter 4 looks at the development of specialized switches to meet the more complex requirements of large networks, data center networks, and Internet Service Providers, while Chapter 5 describes some advanced switch features. Appendix A lists resources for further information.

Figure 1. Topics discussed in this guide