Specifications
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Switches typically indicate their performance in per port rates and in backplane or internal rates
(both in bit rates and in packets per second). The port rates indicate the maximum rates on
specic ports. This means that the speed of a switch, for example 100 Mbit/s, is often the per-
formance of each port.
Figure 9.1c With a network switch, data transfer is managed very eciently as data trac can be directed from one
device to another without aecting any other ports on the switch.
A network switch normally supports dierent data rates simultaneously. The most common rates
used to be 10/100, supporting 10 Mbit/s as well as Fast Ethernet. However, 10/100/1000 are
quickly taking over as the standard switch, thus supporting 10 Mbit/s, Fast Ethernet and Gigabit
Ethernet simultaneously. The transfer rate and mode between a port on a switch and a connected
device are normally determined through auto-negotiation, whereby the highest common data rate
and best transfer mode are used. A switch also allows a connected device to function in full-duplex
mode, i.e. send and receive data at the same time, resulting in increased performance.
Switches may come with dierent features or functions. Some switches include the function of a
router (see section 9.2). A switch may also support Power over Ethernet or Quality of Service (see
section 9.4), which controls how much bandwidth is used by dierent applications.
CHAPTER 9 - NETWORK TECHNOLOGIES