Tom's Hardware and Que Publishing are partnering up to give you four chapters from Scott Mueller's Upgrading And Repairing PCs, 20th Edition. This forth installment is a continuation of the third chapter we're making available from Scott's book, which covers Local Area Network (LAN) hardware and assembly. Don't forget to check out the previous chapters published on Tom's Hardware, Computer History 101: The Development Of The PC, Hard Drives 101: Magnetic Storage and LAN 101: Networking Basics. In the days to come, we'll also present a comprehensive look at Power Supplies.

The choice of a data-link protocol affects the network hardware you choose. Because the various flavors of Ethernet and other data-link protocols use different hardware, you must select the architecture before you can select appropriate hardware, including NICs, cables, and switches.

NICs for Wired Ethernet Networks

On most computers, a wired Ethernet network adapter is integrated into the motherboard. If the integrated component fails or is not fast enough, a replacement NIC can be added through the PCI or PCI Express slot (desktop computers), USB, CardBus PC Card (PCMCIA), or ExpressCard slot on a laptop.

Network adapters (both wired and wireless) have unique hardware addresses coded into their firmware. The hardware address is known as the MAC address. You can see the MAC address on a label on the side of the adapter, or you can view it after the adapter is installed with an OS utility such as the Windows ipconfig.exe command. The data-link layer protocol uses these addresses to identify the other systems on the network. A packet gets to the correct destination because its data-link layer protocol header contains the hardware addresses of both the sending and receiving systems.

Most motherboards have wired Ethernet adapters built-in, whereas discrete Ethernet network adapters range in price from less than $10 for client adapters to more than $100 for single or multiport server-optimized adapters.

Although you can connect two computers directly to each other via their Ethernet ports with a crossover cable, larger networks need a switch, which is frequently incorporated into a router. The network runs at the speed of the slowest component, so if you use a switch that runs at a slower speed than the network clients, the clients connected to that switch will run at that slower speed. Many wireless routers now include 1000 Mb/s gigabit Ethernet ports instead of slower 100 Mb/s Fast Ethernet ports.

When connecting systems on wired Ethernet networks, the following sections contain my recommendations on the features you need.

Speed

Your NIC should run at the maximum speed you want your network to support. Most gigabit Ethernet and Fast Ethernet cards also support slower speeds, meaning, for example, that a 1000 Mb/s (gigabit Ethernet) card also supports 100 Mb/s (Fast Ethernet) speed or standard Ethernet’s 10 Mb/s speed, allowing the same card to be used on both older and newer portions of the network. To verify multispeed operation, look for network cards identified as 10/100 or 10/100/1000 Ethernet. All modern Fast or gigabit NICs should also support full-duplex operation:

• Half-duplex means that the network card can only send or only receive data in a single operation.
• Full-duplex means that the network card can both receive and send simultaneously. Full-duplex options boost network speed if switches are used in place of hubs. For example, 1000 Mb/s gigabit Ethernet cards running in full-duplex mode have a maximum true throughput of 2000 Mb/s, with half going in each direction.

Note: Unlike hubs, which broadcast data packets to all computers connected to them, switches create a direct connection between the sending and receiving computers. Therefore, switches provide faster performance than hubs; most switches also support full-duplex operation, doubling the rated speed of the network when full-duplex network cards are used.

For more information about switches, see Scott Mueller's Upgrading And Repairing PCs, 20th Edition, “Switches for Ethernet Networks,” p. 816 (this chapter).

Bus Type

If you need to install a network adapter for use with a gigabit Ethernet (10/100/1000 Mb/s) network, any of the following buses have more than adequate performance:

• PCI/PCIe. The integrated NIC built in to most motherboards are either PCI or PCIe devices.
• CardBus/ExpressCard (laptop computers).

All of these buses support gigabit Ethernet adapters without limiting throughput. Integrated network adapters use either the PCI or PCI Express bus to connect to the system, both of which have more than enough bandwidth. Note that USB 2.0 (480 Mb/s) is not on that list because it is simply not fast enough to fully support gigabit Ethernet’s 1000 Mb/s bandwidth; however, 100 Mb/s Ethernet connections will work on USB 2.0 with no problems. USB 3.0 would be more than fast enough to support a gigabit Ethernet adapter, however there aren’t any network adapters I know of using USB 3.0.