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Networking Devices

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Network cards

Network cards, also called Network Interface Cards, are devices that allow computers to connect to the network.

When specifying or installing a NIC, you must consider the following issues:

  • System bus compatibility—If the network interface you are installing is an internal device, bus compatibility must be verified. The most common bus system in use is the Peripheral Component Interconnect (PCI) bus, but some older systems may still use Industry Standard Architecture (ISA) expansion cards.

  • System resources—Network cards, like other devices, need IRQ and memory I/O addresses. If the network card does not operate correctly after installation, there might be a device conflict.

  • Media compatibility—Nowadays, the assumption is that networks use twisted-pair cabling, so if you need a card for coaxial or fiber-optic connections you must specify this. Wireless network cards are also available.

More so even than the assumption that you are using twisted-pair cabling is that the networking system being used is Ethernet. If you require a card for another networking system such as Token Ring, this must be specified when you order.


When working on a Token Ring network, you have to ensure that all network cards are set to transmit at the same speeds. NICs on an Ethernet network can operate at different speeds.

To install or configure a network interface you will need drivers of the device, and may need to configure it, although many devices are now plug and play. Most network cards are now software configured. Many of these software configuration utilities also include testing capabilities. The drivers and software configuration utilities supplied with the cards are often not the latest available and so it is best practice to log onto the Internet and download the latest drivers and associated software.

ISDN adapters

Integrated Services Digital Networking (ISDN) is a remote access and WAN technology that can be used in place of a Plain Old Telephone System (POTS) dial-up link if it is available. The availability of ISDN depends on whether your local telecommunications service provider offers the service, the quality of the line to your premises, and your proximity to the provider's location. ISDN offers greater speeds than a modem and can also pick up and drop the line considerably faster.

If ISDN is available and you do elect to use it, a special device called an ISDN terminal adapter is needed to connect to the line. ISDN terminal adapters can be add-in expansion cards, external devices that connect to the serial port of the system, or specialized interfaces built into routers or other networking equipment. The ISDN terminal adapter is necessary because, although it uses digital signals, the signals are formatted differently from those used on a LAN. In addition, ISDN can create multiple communication channels on a single line.

More information on ISDN is provided in Chapter 6.

System area network cards

System area network cards are interfaces installed for the purpose of connecting computer systems in a cluster. Clustering is a principle by which server systems are configured, and operate, as a single unit. In addition to providing increased processing and storage capabilities, it is also possible to configure servers to be fault-tolerant in either a compensatory or fail-over capacity.

In order for the systems in a cluster to communicate, network interfaces are installed that allow them to communicate directly without the need to use standard network links. These cards are normally high-performance units that utilize either twisted-pair or fiber-optic cabling. If there are only two systems in the cluster, a special cable can connect the two systems directly. If there are more than two, a hub is used to facilitate the connection.


Some clustering configurations allow a standard network link to be used as the communications path. This approach is not recommended, because excessive network traffic or a failure in an intermediary network device will cause network communication to fail and thus make the cluster think that the other system has failed.

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