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categories are recommended for network video systems. Most interfaces are backwards compat-
ible with 10 and 100 Mbit/s Ethernet and are commonly called 10/100/1000 interfaces.
For transmission over longer distances, fiber cables such as 1000BASE-SX (up to 550 m/1,639 ft.)
and 1000BASE-LX (up to 550 m with multimode optical fibers and 5,000 m with single-mode
fibers) can be used.
Figure 9.1b Longer distances can be bridged using fiber optic cables. Fiber is typically used in the backbone of a
network and not in nodes such as a network camera.
10 Gigabit Ethernet
10 Gigabit Ethernet is the latest generation and delivers a data rate of 10 Gbit/s (10,000 Mbit/s),
and a fiber optic or twisted pair cable can be used. 10GBASE-LX4, 10GBASE-ER and 10GBASE-SR
based on an optical fiber cable can be used to bridge distances of up to 10,000 m (6.2 miles). With
a twisted pair solution, a very high quality cable (Cat-6a or Cat-7) is required. 10 Gbit/s Ethernet
is mainly used for backbones in high-end applications that require high data rates.
9.1.2. Switch
When only two devices need to communicate directly with one another via a twisted pair cable,
a so-called crossover cable can be used. The crossover cable simply crosses the transmission pair
on one end of the cable with the receiving pair on the other end and vice versa.
To network multiple devices in a LAN, however, network equipment such as a network switch is
required. When using a network switch, a regular network cable is used instead of a crossover
cable.
The main function of a network switch is to forward data from one device to another on the
same network. It does it in an efficient manner since data can be directed from one device to
another without affecting other devices on the same network.
How it works is that a switch registers the MAC (Media Access Control) addresses of all devices
that are connected to it. (Each networking device has a unique MAC address, which is made up
of a series of numbers and letters that is set by the manufacturer and the address is often found
on the product label.) When a switch receives data, it forwards it only to the port that is con-
nected to a device with the appropriate destination MAC address.
NETWORk TECHNOLOGIES - CHAPTER 9
