Cable specifications

Cables have different specifications and expectations. Important considerations related to performance are as follows: 

.                      •           What speeds for data transmission can be achieved? The speed of bit transmission through the cable is extremely important. The speed of transmission is affected by the kind of conduit used.

.                      •           Will the transmissions be digital or analog? Digital or baseband transmission and analog or broadband transmission require different types of cable.  

•           How far can a signal travel before attenuation becomes a concern? If the signal is degraded, network devices might not be able to receive and interpret the signal. The distance the signal travels through the cable affects attenuation of the signal.

Wide-area networks (WANs)

WANs interconnect LANs, which then provide access to computers or file servers in other locations. Because WANs connect user networks over a large geographical area, they make it possible for businesses to communicate across great distances. WANs allow computers, printers, and other devices on a LAN to be shared with distant locations. WANs provide instant communications across large geographic areas. 

Collaboration software provides access to real-time information and resources and allows meetings to be held remotely. WANs have created a new class of workers called telecommuters. These people never have to leave their homes to go to work. 

WANs are designed to do the following: 

.                      • Operate over a large and geographically separated area 

.                      • Allow users to have real-time communication capabilities with other users 

.                      • Provide full-time remote resources connected to local services 

Local-area networks (LANs)

LANs consist of the following components: 

.                      • Computers

.                      • Network interface cards 

.                      • Peripheral devices 

.                      • Networking media 

.                      • Network devices

LANs allow businesses to locally share computer files and printers efficiently and make internal communications possible. A good example of this technology is e-mail. LANs manage data, local communications, and computing equipment.

Some common LAN technologies include the following: 

.                      • Ethernet

.                      • Token Ring

• FDDI The next page will introduce wide-area networks (WANs).

Network topology

Network topology defines the structure of the network. One part of the topology definition is the physical topology, which is the actual layout of the wire or media. The other part is the logical

that are commonly used are as follows:

•           A bus topology uses a single backbone cable that is terminated at both ends. All the hosts connect directly to this backbone. 

.                      •           A ring topology connects one host to the next and the last host to the first. This creates a physical ring of cable. 

.                      •           A star topology connects all cables to a central point. 

.                      •           An extended star topology links individual stars together by connecting the hubs or switches.

.                      •           A hierarchical topology is similar to an extended star. However, instead of linking the hubs or switches together, the system is linked to a computer that controls the traffic on the topology.               

Testing connectivity with ping

Ping is a utility used to verify Internet connectivity. It is named after the sonar operation used to locate and determine the distance to an underwater object. 

The ping command works by sending multiple IP packets to a specified destination. Each packet sent is a request for a reply. The output response for a ping contains the success ratio and round-trip time to the destination. From this information, it is possible to determine if there is connectivity to a destination. The ping command is used to test the NIC transmit/receive function, the TCP/IP configuration, and network connectivity.

Overview of high-speed and dial-up connectivity

In the early 1960s, modems were introduced to provide connectivity for dumb terminals to a centrally based computer. Many companies used to rent computer time due to the expense of owning an on-site system, which was cost prohibitive. The connection rate was very slow, 300 bits per second (bps), translating to about 30 characters per second.

As PCs became more affordable in the 1970s, Bulletin Board Systems (BBS) appeared. These BBSs allowed users to connect and post or read messages on a discussion board. Running at 300 bps was acceptable, as this exceeds the speed at which most people can read or type. In the early 1980s, use of bulletin boards increased exponentially and the 300 bps speed quickly became too slow for the transfer of large files and graphics. By the 1990s modems were running at 9600 bps and reached the current standard of 56 kbps (56,000 bps) by 1998.Inevitably the high-speed services used in the corporate environment, such as Digital Subscriber Line (DSL) and cable modem access, moved to the consumer market.

Network interface card

A network interface card (NIC) is a printed circuit board that provides network communication  capabilities to and from a personal computer.

Also called a LAN adapter, it resides in a slot on the motherboard and provides an interface connection to the network media. The type of NIC must match the media and protocol used on the local network.

The NIC communicates with the network through a serial connection and with the computer through a parallel connection. The NIC uses an Interrupt Request (IRQ), an I/O address, and upper memory space to work with the operating system. An IRQ is a signal informing the CPU that an event needing attention has occurred. An IRQ is sent over a hardware line to the microprocessor when a key is pressed on the keyboard. Then the CPU enables transmission of the character from the keyboard to RAM. An I/O address is a location in the memory used to enter data or retrieve data from a computer by an auxiliary device. Upper memory refers to the memory area between the first 640 kilobytes (KB) and 1 megabyte (MB) of RAM.