A computer
network or data network is a telecommunications network which allows computers
to exchange data. In computer networks,
networked computing devices exchange data with each other using a data link.
The connections between nodes are established using either cable media or
wireless media.
The network operates by
connecting computers and peripherals using two pieces of equipment; switches
and routers. Switches and routers, essential networking basics, enable the
devices that are connected to your network to communicate with each other, as
well as with other networks.
The Purpose of Networks
Consider a sampling of
applications that can travel over a network’s connections:
- File sharing between two computers
- Video chatting between computers located in different parts of the world
- Surfing the web (for example, to use social media sites, watch streaming video, listen to an Internet radio station, or do research for a school term paper)
- Instant messaging (IM) between computers with IM software installed
- Voice over IP (VoIP), to replace traditional telephony systems
Overview of
Network Components
• Designing,
installing, administering, and troubleshooting a network requires the ability
to recognize various network components and their functions.
• The
components to consider for now are client, server, hub, switch, router, media,
and wide-area network (WAN) link.
Client:
• The
term client defines the device an end user uses to access a network.
• E.g.
workstation, laptop, smartphone with wireless capabilities, or a variety of
other end-user terminal devices.
Server:
• A
server , as the name suggests, serves up resources to a network.
• E.g.
e-mail access as provided by an e-mail server, web pages as provided by a web
server, or files available on a file server.
Hub:
• A
hub is an older technology that interconnects network components, such
as clients and servers.
• However,
for scalability, hubs can be interconnected, up to a point.
• If
too many hubs are chained together, network errors can result.
• A
hub does not perform any inspection of the traffic it simply receives traffic
and repeats that traffic out all of the other ports.
Switch:
• A
switch interconnects network components, and they are available with a
variety of port densities.
• A
switch does not simply take traffic, rather it learns which devices reside off
of which ports.
• As
a result, when traffic comes in a switch port, the switch interrogates the
traffic and forwards the traffic out of the appropriate port, and not out all
of the other ports.
• A
switch makes forwarding decisions based on addresses that are physically burned
into a network interface card (NIC) installed in a host (that is, any
device that transmits or receives traffic on a network).
• This
burned-in address is a Media Access Control (MAC) address.
Router:
• A
router makes forwarding decisions based on logical network addresses.
• Most
modern networks use Internet Protocol (IP) addressing.
• Routers
know what logical IP networks reside off of which router interfaces.
• Then,
when traffic comes into a router, the router examines the destination IP
address of the traffic and, based on the router’s database of networks (that
is, the routing table), the router intelligently forwards the traffic out the
appropriate interface.
TYPES OF NETWORK
Networks Defined by Geography
One criterion by which we can classify networks is
how geographically dispersed the networks components are.
• Local-area
network (LAN)
• Wide-area
network (WAN)
• Campus-area
network (CAN)
• Metropolitan-area
network (MAN)
• Personal-area
network (PAN)
1) LAN
• A
LAN interconnects network components within a local region (for example, within
a building).
• Examples
of common LAN technologies you’re likely to encounter include Ethernet (that
is, IEEE 802.3) and wireless networks (that is, IEEE 802.11).
2) WAN
• A
WAN interconnects network components that are geographically separated.
• E.g.
two or more campuses with multiple WAN
connected to the main campus using Multiprotocol Label Switching (MPLS),
Asynchronous Transfer Mode (ATM), and Frame Relay.
3) CAN
(Campus Area Network)
• Universities
may have several dozen buildings each having a LAN.
• However,
those building-centric LANs were interconnected.
• By
interconnecting these LANs, another network type was created, a CAN.
• Besides
an actual
• university
campus, a CAN might also be found in an industrial park or business park.
4) MAN
(Metropolitan Area Network)
More widespread than a CAN and less widespread than a
WAN, a MAN interconnects locations scattered throughout a metropolitan area.
Imagine that a business in Abuja had a location near
Airport, another location near the Aso Rock, and another location in the Area
I.If a service provider could interconnect those locations using a high-speed
network, the interconnection of those locations would constitute a MAN.
One example of a MAN technology is Metro Ethernet
5) PAN
(Personal Area Network)
A PAN is a network whose scale is even smaller than a
LAN.
As an example, a connection between a PC and a
digital camera via a universal serial bus (USB) cable could be
considered a PAN.
Another example is a PC connected to an external hard
drive via a FireWire connection.
A PAN, however, is not necessarily a wired
connection. A Bluetooth connection between your cell phone and your car’s audio
system is considered a wireless PAN (WPAN).
The main distinction of a PAN, however, is that its
range is typically limited to just a few meters.
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