UNIT 6:
Networks
and
Networking
Objectives:
Networking concepts.
Types of networks.
Describe kinds of network topologies.
Local area network concepts, terminology.
Identify:
sources of data
data communications hardware
transmission media
Connectivity
Connectivity pertains to the
degree to which hardware
devices, software, and databases
can be functionally linked to one
another. It is implemented in
steps & various tools.
Why Networking?
Computer networks enhance the
efficiency and effectiveness of the
interaction between people and
resources in different locations.
Interface (connect) a diverse set of
hardware, software, and databases.
Converge media types so that
information will be more easily
accessible to more people.
Global village NEEDS networks
Networking Concepts
Intranet : Closed or private version of the
Internet. Intranets use Internet technologies on
an in-house network.
A private network whose hosts cannot exchange
messages with hosts outside of the private
network, unless messages pass through socalled firewalls (which control flow of
messages in network) and use same types of
hosts, routers , links and protocols as public
Internet.
Networking Concepts
Extranet Extension of an intranet in
that it is partially accessible to authorized
outsiders, such as customers and
suppliers.
Intracompany
networking
Networks set up within a company.
Intercompany networking
Companies cooperating externally
with other companies and customers.
Another name for this is B2B, or
business-to-business e-commerce.
E-commerce Electronic commerce :
describes business conducted online.
B2B relies on computer networks &
the Internet to transmit data.
Backbone Collective term - a
system of routers, gateways, other
communications hardware, and
the associated transmission
media (cables, wires, and wireless
links) that link the computers in an
organization.
Node Endpoint in a network.
Four (4) main Types of Networks
Networks are classified by the proximity of nodes
(how close nodes are to each other and size of
network)
LAN Local Area Network; connects nodes
in close proximity, such as in a building.
resources can be shared - applications
software, I/O devices, storage devices.
CAN: Campus Area Network - LAN operating
within a single organization that leases
Internet access directly from regional or
national carrier, e.g. The U.W.I.
Types of Networks
WAN Wide area network
biggest type of network
Connects nodes in widely dispersed
geographic areas, such as cities,
states, or countries.
MAN Metropolitan area
network - designed for a city.
MANs are smaller than WANs but
larger than LANs.
Basic hardware components
in LAN(Local Area Network)
1. the NIC,
2. transmission media,
3. servers.
Network Interface Card
(NIC)
Add-on board or PC card that enables
and controls the exchange of data
between the PCs in a LAN.
A card installed in a slot in the PC to
allow communication between the PC
and other PCs in the LAN and beyond
NETWORKS SETUP
Ethernet: In the Ethernet access
method, nodes on the LAN must gain
access to send a message. When two
computers start to send information at the
same time, one must wait until the other
computer is finished. This happens very
quickly.
Network Topology
Description of the possible
physical layout and
connections of nodes within a
network.
Types of Network Topologies
Star topology Centralized host computer connected to
several other computer systems.
Communication is performed through the host.
Ring topology computer systems of about the same
size;
no one computer as the focal point of the network.
Messages passed around the ring until reach their
destination.
Bus topology Includes terminals, peripheral devices &
PCs connected along a common cable called a network
bus.
A message signal is broadcast to the nodes, but only
destination node responds.
Types of Network
topologies
A STAR
TOPOLOGY
B RING
TOPOLOGY
C BUS
TOPOLOGY
Data Communication
HARDWARE:
Data communication
Electronic collection and distribution of
information between two points.
Data communications hardware transmits
digital information :
between terminals and computers or
between one computer and other computers.
A: Client and Server
Computers
A server computer is one or more central
computer(s) in a network. The server
computer manages the network and
performs a variety of functions for the
other computers on the network, the
client computers.
Client computer Usually a PC or
workstation; linked to the server computer.
Client/server computing When a
server computer supports many client
computers.
Client and Server Computers
Proxy server computer
Computer that sits between the client PC
and a normal server and handles as many
client requests as possible, routing only
those requests that it cannot handle to the
real server.
Filters external and internal network
access.
LAN Transmission Media and
Servers
The following figure illustrates how nodes in a
LAN are connected using a bus topology &
popular servers.
The server is the component that can be
shared by users on the LAN.
Three popular servers are the file server,
the print server, and the communications
server.
File server
Usually a dedicated
computer with a
high-capacity hard
disk for storing the
data and programs
shared by the
network users.
Print server
Handles user print
jobs and controls at
least one printer.
Communications
server Provides
communication
links external to the
LAN to other
networks.
Communications
Hardware
The Standard
Telephone-Link
Modem
Most PCs have an internal modem.
Standard telephone lines transmit analog signals
BUT computer data is digital
THUS, a modem is needed to:
convert the digital signals into analog
signals (modulate) while the data travels
through the phone lines
converts the signals back to digital
(demodulates) so the receiver computer
can interpret received data.
Other Modems
Cable modem Modulates digital signals
to radio frequency carrier signals.
DSL (digital subscriber line) Not really
a modem; Rather, it is a DSL transceiver provides connection between the users
computer /network and DSL line.
Satellite modem Device to enable
uplink and downlink from a satellite;
composed of two modems: one for uplink
conversions and the other for downlink
conversions.
Routers
Router Bridges the gap between
incompatible networks by
performing the necessary
protocol conversions to route
messages to their proper
destinations.
Router
A router is the smartest and most
complicated of the bunch.
Routers come in all shapes and sizes from
small broadband routers that are very
popular right now to the large industrial
strength devices that drive the Internet
itself.
All routers include some kind of user
interface for configuring how the router will
treat traffic.
Example : LinkSys 160n Router
LinkSys Router WRT160N
with 2 WRT54 Antenna.
Hubs
Multi-port device that expands the number
of nodes that can be linked to a network.
least expensive, least intelligent, and least
complicated of the three.
simple hubs WHY? Gives quick and easy
ways to connect computers in small
networks.
Hubs
very simple job : anything that comes in one
port is sent out to the others.
Every computer connected to the hub "sees"
everything that every other computer on the
hub sees.
The hub itself is ignorant of data being
transmitted.
Hubs
Switch
Multi-port device for a LAN, similar to a
hub.
Full-duplex, enables transmission in both
directions at the same time to improve
overall network performance.
A switch does essentially what a hub does
but more efficiently.
Special-Function Terminals:
ATMs and POSs
Terminals enable input to and output
from a remote computer system.
Special-function terminals are
designed for a specific purpose, such
as is the case with ATMs (automatic
teller machine) and POS (point-ofsale) terminals.
Data Communications
Channels OR Transmission
Media
Communication
s channel
Medium through
which digital
information must
pass to get from
one location in a
computer
network to the
next.
Data Transmission in
Practice
Physical Transmission Media
using wire
Twisted-Pair Wire:
Telephone Line
Cat5 & Cat5e cabling
4 twisted pairs of wire : 100 Mbps, 1 G bps.
Twisted-pair wire is regular phone wire - two
copper wires twisted together.
Both dialup Internet service and DSL (digital
subscriber line) are delivered over POTS (plain old
telephone service).
Coaxial Cable
Commonly known as
cable in cable television.
Coaxial cables have a very wide pipe
A copper wire -permits high-speed data
transmission
minimal signal distortion.
hundreds of times faster than POTS
Fiber Optic Cable
Light Pulse - Carries data as laser-generated
pulses of light.
made of bundles of very thin, transparent,
almost hair-like fibers
transmits data more inexpensively and much
more quickly than do copper wire
transmission media.
The Internet backbone is mostly fiber optic
cable.
Wireless Communication /
Transmission Media
(No physical wire)
Microwave signals
Radio signals
Wireless Application Protocol allows
wireless Internet access via handheld
devices, such as cellular phones.
Communications Satellites:
Microwave signals are bounced off
satellites, avoiding obstructions
Wireless Communication /
Transmission Media
(No physical wire)
Cellular, digital cellular, satellite
Wireless LAN PC card
Transceiver with a limited range (about 50 to
300 feet).
It links computers via omnidirectional radio
waves to communications hubs, called access
points.
WHY?? Down to Earth Wireless:
Wi-Fi and Wireless-a/g
Popular communications standards used to
enable devices and PCs to talk to one another:
Wi-Fi or Wireless-B (IEEE 802.11b standard),
Wireless-A/G (IEEE 802.11a/g standard),
Eliminates biggest expenses in a
computer network of installing physical
links between the components.
Wi-Fi and Bluetooth
Wi-Fi excellent range up to 300 ft
Most popular longwire replacement
technology in LANs
reasonable transmission speed (11 M bps)
High-speed, fixed broadband wireless LAN
Bluetooth range of 30 feet.
Considerably slower (1 M bps) shortwire
replacement technology
Low-speed, short range connection
Summary Media Transmission Types
Cable
Physical wire
Twisted pair, coaxial, fiber optic
Wireless
There are three types of cable
Twisted pair - Originally used to connect a
telephone to a wall jack
Optical fiber
Coaxial - The cable in cable TV
Wireless technology
