Transcript - PebblePad

Networks
What is a network ?
A group of computers
and associated devices
connected by
communications facilities
(both hardware and
software) to share
information and
peripheral devices, such
as printers and modems.
LAN?
WAN?
PAN?
MAN?
LAN or WAN ?
LAN
Local area network
WAN
Wide area network
PAN
Personal area network
MAN
Metropolitan area network
Network protocol
A protocol is a set of rules that governs the communication
Between computers on a network
Network protocols include:
•Ethernet (most widely used)
•Localtalk
•Token ring
Ethernet

Each computer listens along the cable to see if it is
clear before they transmit data through the network,if
the network is clear the node (usually a computer)
will transmit or wait for the line to be clear.

If 2 nodes (computers) attempt to transmit at the
same time a collision will occur, each computer will
then back off, wait and retransmit
Network Topologies - Bus
Server
PC
PC
PC
Bus topology
Advantages


Easy to connect pc or
peripheral
Requires less cabling than
other topologies
Disadvantages



Entire network breaks down
if there is a break in the main
cable
Difficult to identify where the
problem is coming from if
network crashes
Cannot be used as a stand
alone solution in large
buildings
Network Topologies - Ring
PC
PC
PC
Server
PC
Ring topology
Advantages



All nodes have equal access
Growth in the system has
minimal effect on
performance
Because data travels in one
direction high data
transmission speeds are
enabled
Disadvantages


Often the most expensive
topology
Failure of one computer may
affect others
Network Topologies - Star
PC
Hub or
Switch
PC
PC
Server
PC
Star topology
Advantages



Easy to install and wire
No disruption to the the
network when connecting or
removing devices
Easy to detect faults and
remove parts
Disadvantages



Requires more cable than a
bus
If the hub fails the nodes
attached are disabled
More expensive than a bus
Network Topologies - Wireless
PC
PC
Wireless Hub or
Switch
Server
PC
Wireless topology
Advantages



No cables
Can use remote access
points (hotspots)
Can convert wired networks
to become wireless relatively
inexpensively
Disadvantages


Data transfer speeds can be
slower than cable networks
Signal strength can
sometimes be weak
depending on location
Network Topologies - Hybrid
PC
Wireless
Hub or
Switch
Hub or
Switch
Server
PC
PC
Network Topologies - Hybrid
PC
Wireless
Hub or
Switch
Hub or
Switch
Server
PC
Classroom / Office
Hybrid topology
Advantages


One company can combine
benefits of several different
types of topology
Workgroup efficiency can be
customised
Disadvantages

Devices on one topology
can’t be placed onto another
topology without some
hardware changes
Network Interface Cards
Allows a computer to be connected to a network.
Must be the right type for the network (e.g. Ethernet,
Token Ring).
RJ45 Connector
Network Cabling
•Depends on the network type, speed of operation
and distance covered.
Common types are:
Twisted pair wire (Ethernet)
Fibre Optic (FDDI)
Bluetooth
PAN – Personal area network
• Named (bizarrely) after a 10th century Danish king
• Replacing infrared as the instant transfer mode of
choice with a better range and no line of sight
restrictions
• Allows up to 8 devices to connect as a mini network
(short range of 30ft)
• Devices include – Mobile phones, printers, PDA’s,
GPS, digital cameras, keyboards and mice
Centrino technology
Intel has branded a combination of
technologies used in laptops under one
name
Pentium M (mobile) chip
Wireless network connection capability
855 chipset (including graphics chip)
Only Centrino if all 3 components
included
Cable vs wireless
Cabled network
Pro’s
• Inexpensive
• Capabilty included on most
pc’s
Wireless networks
Pro’s
• No cabling
• Can use wireless access
points anywhere (Hotspots)
Cons
• Requires cabling
• Additional hardware
required for bigger
networks such as hubs and
switches
Cons
• Data speeds slower than
Cabled networks
• Wireless capability only
available on newer pc’s
Range
• 91m (300ft) per segment
Range
• 30m (100ft)
Sharing Information
Once PCs are networked, users may share each
other files, printers and Internet connection.
PC
Hub or
Switch
PC
Printer
PC
Internet
Network Operating System
For much greater control over the sharing, access
and security of files on a network.
Familiar systems are:
MS Windows 2000 Professional.
Novelle Netware.
Internet
The interconnection of a number of
networks across the globe.
Connected by a backbone of
telephone lines, high speed ISP cable,
satellite, undersea cable and wireless
links.
The different parts of the Internet (or
any large WAN) are connected
together using a number of devices
including: Bridges, Routers,
Repeaters and Switches.
Connecting to the Internet
There are two types of Internet connection:
Analogue – via a modem (typically 56 kBps)
Broadband – via a broadband modem (typically
256 kbps, 512 kbps, 1 Mbps or 2 Mbps)
Installing Broadband
• You need to be in an area of broadband
coverage (i.e you need an Asynchronous
Digital Subscriber Network – ADSN –
and BT need to reconfigure you to it).
• You need to sign up with a company to
give you broadband (e.g. BT, Telewest).
• You need a Broadband modem.
Typical Broadband Configuration
Modem could be wireless
Internet website suffixes
.com or .co
Commercial site, generally going to shed a
Positive light on its product as always money behind it
.edu or .ac
Academic or educational institutions
.org
Traditionally non-profit organisations, such as the
Red cross, though sometimes there may be commercial
Interests if the site is being sponsored
.gov
Government sites
.net
Network, any kind of site can have this suffix as it
Acts as a catch all for any sites not fitting into the other
catorgories
Example country domain suffixes
.uk United Kingdom
.au Australia
.in India
.br Brazil
.it Italy
.ca Canada
.mx Mexico
.fr France
.tw Taiwan
.il Israel
Exercise / Activity
This week – Exercise 1 (network questions).
Next week - Construct a small network.