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Introduction
Advance Mobile Computing
1
Wired Networks
Wired networks, also called Ethernet networks, are the most
common type of local area network (LAN) technology. A
wired network is simply a collection of two or more
computers, printers, and other devices linked by Ethernet
cables. Ethernet is the fastest wired network protocol, with
connection speeds of 10 megabits per second (Mbps) to 100
Mbps or higher.
2
Ethernet Cable

Ethernet cable is a popular type of network cable used for
high-speed networking between two devices. Ethernet
cables have been evolving since the beginning of the
Ethernet standard in 1985. Many different categories of
Ethernet cable have been developed, and each category has
different specifications as far as shielding from
electromagnetic interference, data transmission speed, and
the possible bandwidth frequency range required to
achieve that speed. It is understandable that some
confusion can arise when looking at all the available
options for Ethernet cabling.
3
Types of Ethernet Cable
There are also certain types of cables recognized as common
industry standards.
Category 3
It is also known as Cat 3 or station wire, is one of the oldest forms of Ethernet
cable still in use today. It is an unshielded twisted pair (UTP) cable that is capable
of carrying 10 megabits per second (Mbps) of data or voice transmissions. Its
maximum possible bandwidth is 16 MHz. Cat 3 cable reached the peak of its
popularity in the early 1990s.
4
Category 5

Category 5 ( Cat 5) Ethernet cable is the successor to the earlier Category 3.
Like Cat 3, it is a UTP cable, but it is able to carry data at a higher transfer rate.
Cat 5 cables introduced the 10/100Mbps speed to the Ethernet, which means
that the cables can support either 10 Mbps or 100 Mbps speeds. A 100 Mbps
speed is also known as Fast Ethernet, and Cat 5 cables were the first Fast
Ethernet-capable cables to be introduced. They also can be used for telephone
signals and video, in addition to Ethernet data.
5
Category 5e

The Category 5 e standard is an enhanced version of Cat 5 cable,
which is optimized to reduce crosstalk, or the unwanted
transmission of signals between data channels. This category works
for 10/100 Mbps and 1000 Mbps (Gigabit) Ethernet, and it has
become the most widely used category of Ethernet cable available
on the market. While Cat 5 is common in existing installations, Cat
5e has completely replaced it in new installations. While both Cat 5
and Cat 5e cables contain four twisted pairs of wires, Cat 5 only
utilizes two of these pairs for Fast Ethernet, while Cat 5e uses all
four, enabling Gigabit Ethernet speeds. Bandwidth is also increased
with Cat 5e cables, which can support a maximum bandwidth of
100 MHz. Cat 5e cables are backward compatible with Cat 5
cables, and can be used in any modern network installation.
6
Category 6

One of the major differences between Category 5e and the
newer Category 6 is in transmission performance. While Cat
5e cables can handle Gigabit Ethernet speeds, Cat 6 cables are
certified to handle Gigabit Ethernet with a bandwidth of up to
250 MHz. Cat 6 cables have several improvements, including
better insulation and thinner wires, that provide a higher
signal-to-noise ratio, and are better suited for environments in
which there may be higher electromagnetic interference. Some
Cat 6 cables are available in shielded twisted pair (STP) forms
or UTP forms.
7
Category 6a

Category 6 a cable or augmented Category 6 cable,
improves upon the basic Cat 6 cable by allowing 10,000
Mbps data transmission rates and effectively doubling the
maximum bandwidth to 500 MHz. Category 6a cables are
usually available in STP form, and, as a result, must have
specialized connectors that ground the cable.
8
Category 7

Category 7 cable, also known as Class F, is a fully shielded cable that
supports speeds of up to 10 Gbps (10,000 Mbps) and bandwidths of up to 600
Mhz. Cat 7 cables consist of a screened, shielded twisted pair (SSTP) of
wires, and the layers of insulation and shielding contained within them are
even more extensive than that of Cat 6 cables.
9
Comparisons of Cables
Cable Type
Maximum
Data
Transmission
Speed
Maximum
Bandwidth
Category 3
UTP
10 Mbps
16 MHz
Category 5
UTP
10/100 Mbps
100 MHz
Category 5 e
UTP
1000 Mbps
100 MHz
UTP or STP
1000 Mbps
250 MHz
Category 6 a
STP
10,000 Mbps
500 MHz
Category 7
SSTP
10,000 Mbps
600 MHz
Category 6
10
Topologies


There are three basic network topologies that are most commonly used today.
The star network, a general more simplistic type of topology, has one central
hub that connects to three or more computers and the ability to network
printers. This type can be used for small businesses and even home networks.
The star network is very useful for applications where some processing must be
centralized and some must be performed locally. The major disadvantage is the
star network is its vulnerability. All data must pass through one central host
computer and if that host fails the entire network will fail.
11
Bus Topologies

Bus network has no central computer and all computers are linked on a
single circuit. This type broadcasts signals in all directions and it uses
special software to identify which computer gets what signal. One
disadvantage with this type of network is that only one signal can be
sent at one time, if two signals are sent at the same time they will collide
and the signal will fail to reach its destination. One advantage is that
there is no central computer so if one computer goes down others will
not be affected and will be able to send messages to one another.
12
Ring Topologies

The ring network Similar to the bus network, the ring network
does not rely on a central host computer either. Each computer
in the network can communicate directly with any other
computer, and each processes its own applications
independently. A ring network forms a closed loop and data is
sent in one direction only and if a computer in the network fails
the data is still able to be transmitted.
13
Wireless Networks


A wireless network, which uses high-frequency radio waves
rather than wires to communicate between nodes, is another
option for home or business networking. Individuals and
organizations can use this option to expand their existing wired
network or to go completely wireless. Wireless allows for
devices to be shared without networking cable which increases
mobility but decreases range.
There are two main types of wireless networking; peer to peer or
ad-hoc and infrastructure.
14
Peer-to-Peer wireless network

An ad-hoc, or peer-to-peer wireless network consists of a number
of computers each equipped with a wireless networking interface
card. Each computer can communicate directly with all of the
other wireless enabled computers. They can share files and
printers this way, but may not be able to access wired LAN
resources, unless one of the computers acts as a bridge to the
wired LAN using special software.
15
Infrastructure Based


An infrastructure wireless network consists of an access
point or a base station. In this type of network the
access point acts like a hub, providing connectivity for
the wireless computers. It can connect or bridge the
wireless LAN to a wired LAN, allowing wireless
computer access to LAN resources, such as file servers
or existing Internet Connectivity.
There are two types of access points:
16
Dedicated hardware access points (HAP)
Dedicated hardware access points (HAP) such as Lucent's
WaveLAN, Apple's Airport Base Station or WebGear's
AviatorPRO. Hardware access points offer comprehensive support
of most wireless features.
17
Software Access Points Based

Software Access Points which run on a computer equipped with a
wireless network interface card as used in an ad-hoc or peer-to-peer
wireless network. The Vicomsoft InterGate suites are software
routers that can be used as a basic Software Access Point, and
include features not commonly found in hardware solutions, such
as Direct PPPoE support and extensive configuration flexibility,
but may not offer the full range of wireless features defined in the
802.11 standard.
18
Transmissions standards for wireless


There are four basic types of transmissions standards for wireless networking.
These types are produced by the Institute of Electrical and Electronic Engineers
(IEEE). These standards define all aspects of radio frequency wireless
networking. They have established four transmission standards; 802.11,
802.11a, 802.11b, 802.11g.
The basic differences between these four types are connection speed and radio
frequency. 802.11 and 802.11b are the slowest at 1 or 2 Mbps and 5.5 and
11Mbps respectively. They both operate off of the 2.4 GHz radio frequency.
802.11a operates off of a 5 GHz frequency and can transmit up to 54 Mbps and
the 802.11g operates off of the 2.4 GHz frequency and can transmit up to 54
Mbps. Actual transmission speeds vary depending on such factors as the
number and size of the physical barriers within the network and any
interference in the radio transmissions.
19
Wired vs. Wireless Networking
The biggest difference between these two types of networks
is one uses network cables and one uses radio frequencies.
A wired network allows for a faster and more secure
connection and can only be used for distances shorter than
2,000 feet. A wireless network is a lot less secure and
transmission speeds can suffer from outside interference.
Although wireless networking is a lot more mobile than
wired networking the range of the network is usually 150300 indoors and up to 1000 feet outdoors.
20
Questions.





What is wireless networking?
What is a wireless network made up of?
What is the range of a wireless network?
How many wireless networked computers can
use a single access point?
Can I have more than one access point?
21
Networks
22
Why are networks so useful?
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They facilitate
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They allow for sharing
of resources
Both of the above
Th
1.
33% 33% 33%
23
Network


Uses of communications technologies
 Internet
 Global Positioning System (GPS)
 Short Message Service (SMS)
Network
 Interconnected group of computers and devices connected via
communications devices and media
 Facilitates sharing of resources and supports communications
 Requires
 Sending & receiving devices
 Communications devices
 Communications channel or path
 Network OS (NOS)
24
Networks –
Communications Devices

Communications Device


Hardware capable of sending/receiving data
Convert signals so that they are suitable for the
communications channel


May convert between analog and digital
Common types






Dial-up modems
ISDN and DSL modems
Cable modems
Network interface cards
Wireless access points
Routers
25
Networks –
Communications Devices

Dial-up Modem


Modulate/demodulate
External modem


Internal modem


Connects to serial or RS-232 port
Card inserted to expansion slot/PC Slot
ISDN and DSL Modems
Do not modulate/demodulate
External
Sends and receives data over a digital
telephone line
ISDN line
DSL line

26
Networks –
Communications Devices

Cable modem




Cable television network
Faster than dial-up access or ISDN line
Splitter runs separate cables to TV’s and cable modem
External


USB port or Ethernet NIC via a cable
Network Interface Card (NIC)




Coordinates transmission/receipt of data to/from the device
Card installed in an expansion slot of a PC, printer, PC slot
Wireless transmission includes antenna
Works with a particular network technology

Ethernet or token ring
27
Networks –
Communications Devices

Hub


Router



Connects multiple
computers and routers
together
Transmits packets to
correct destination
May include built-in
firewall


Provides a central point
of connectivity for cables
in a network
May include a router
Wireless access point


Allows computers and
devices to communicate
wirelessly
Allows data transfer to a
wired network
28
Communications devices include
______.
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hubs
modems
NICs
All of the above
20% 20% 20% 20% 20%
ro
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1.
45
29
Networks –
Communications Channels

Channel


Communications path between two devices
Transmission rate


Speed at which data flows through the channel
Bandwidth of the channel


Bits per second (bps), Hertz (cycles per second)
Transmission media

Materials or techniques capable of carrying one or more signals



Physical transmission media


Baseband media – carry one signal at a time
Broadband media – carry multiple signals concurrently
Twisted pair, Coaxial, Fiber Optic
Wireless transmission media

Infrared, Radio Frequency, Infrared, Microwave
30
Networks –
Physical Transmission Media

Twisted-pair cable


Used for network cabling and telephone
systems
One or more twisted-pair wires bundled
together

Each pair has two insulated copper wires
twisted together

Coaxial cable (coax)
Used for network cabling and cable
TV
Single copper wire surrounded by 3
layers

Insulating material
Woven/braided metal
Plastic outer coating

31
Networks –
Physical Transmission Media

Fiber optic cable


Light used to send signals
Thin glass or plastic strands






optical
fiber
core
Surrounded by insulating glass
cladding and a protective
coating
Carries many signals
High speed
Less noise
Smaller size
Expensive, difficult to install
and modify
glass
cladding
Protective coating
32
Networks –
Physical Transmission Media
33
All of the following except ______ are
examples of physical media.
25% 25% 25% 25%
45
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2.
coaxial cable
twisted pair
microwave cable
fiber optic cable
co
1.
34
Networks –
Wireless Transmission Media

Radio Frequency




Antenna, transmitter,
receiver
Bluetooth (2.45 GHz)
802.11b & g (2.4 GHz)
Cellular Radio Waves
 Cell phones, mobile
devices
 High frequency radio
waves
 824 to 849 MHz

Infrared Signals


Microwaves
High-speed signal transmission
Signals sent between microwave
stations
Fixed-point wireless
Requires line-of-sight
Communications Satellites

Satellite receives microwave
signal and amplifies
Retransmits over wide-area, to
a number of land-based stations

IR light waves with line-of-sight transmission
35
Networks –
Wireless Transmission Media
36
All of the following except ______ are
examples of wireless media.
25% 25% 25% 25%
45
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4.
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3.
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w
av
2.
microwaves
satellites
radio frequency
waves
fiber optic waves
m
ic
1.
37
Networks

Classified according to

Geography – Geographic Distribution






LAN
MAN
WAN
Architecture
Topology
Protocol/Communications Technology
38
Networks –
Geographic Distribution

Local Area Network (LAN)


Connects computers in a limited
geographical area
Each computer and device is a
node

Metropolitan Area Network (MAN)


High-speed network that connects LANs in
a metropolitan area
Managed by a consortium of users or a
single network provider
39
Networks –
Geographic Distribution
Wide Area Network (WAN)

Connects computers and devices in a large
geographical area

Connected via many types of media
One large network or two or more
interconnected LANs, MANs


Others
CAN
HAN
TAN

40
A ______ is a network that encompasses a
limited geographic area.
45
25%
25%
PA
N
LA
N
N
4.
W
A
3.
N
2.
25%
MAN
WAN
LAN
PAN
M
A
1.
25%
41
Networks

Classified according to

Geography

Architecture – Broad outline of the network




Peer-to-Peer
Client/Server
Topology
Protocol/Communications Technology
42
Network Architectures –
Client/Server and Peer-to-Peer

Client/Server

client
client
Server controls resources

More storage space, power



client
Serves as a repository
Dedicated servers
Client relies on the server for
access to resources
printer

server
Peer-to-Peer


Share peripheral devices
Up to 10 “peer” computers


Internet Peer-to-Peer (P2P)


NOS & applications software, storage
Users connect directly to each other’s
hard disk
Popular, inexpensive
43
Networks

Can be classified according to

Geography
Architecture

Topology – Physical arrangement of devices

connected to the network



Bus
Ring
Star


Networks often use a combination of topologies
Protocol/Communications Technology
44
Network Topologies –
Bus and Ring Networks
 Bus Network
Single central cable connects computers and
devices
 Transmits in both directions
 If a device fails, network continues to function
Reliable
 Popular, inexpensive


Ring Network





Cable forms a closed ring
Transmits in only one direction
If one device fails, all those after the
device cannot function
Spans larger distance than bus network
LANs and WANs
45
Network Topologies –
Star and Other Networks

Star Network

Devices connect to a central
computer


If one device fails, only that
device is affected


Hub
Hub fails
Other Topologies

Mesh


Redundant interconnections between nodes
Tree

Star networks connected together via a bus
46
With ______ topology, the devices on the
network are connected together in a
closed loop.
25%
45
25%
tr
ee
St
ar
in
g
4.
R
3.
us
2.
25%
bus
ring
star
tree
B
1.
25%
47
Networks

Can be classified according to

Geography
Architecture
Topology

Protocol/Communications Technology –


Standards that govern how data/instructions flow over
the network





Ethernet
Token Ring
TCP/IP
WAP
Others
48
Networks –
Network Communications Technologies

Communications Protocol

Set of rules and procedures for exchanging
information among computers





Ethernet
Token ring
TCP/IP
WAP
Others
49
Network Communications Technologies –
Ethernet

Ethernet


Widely used LAN standard
Developed by Xerox, DEC, Intel - 1976





Fast Ethernet (100Base-T) - 100 Mbps
Gigabit Ethernet - 1000 Mbps
10-Gigabit Ethernet – 10 Gbps
Bus or star topology
PCs in the network to contend for access

Collision
50
Network Communications Technologies –
Token Ring

Token Ring



Ring or star topology
LAN standard
Passes a signal called a token




Special bit pattern
Only device with token can transmit
Device catches the token, attaches message , sends it to
travel around the network to receiving device
Receiving device catches token, strips off the message,
resends token
51
Network Communications Technologies –
TCP/IP

TCP/IP


Used to connect hosts on the Internet
Includes several protocols


Data broken up into small packets





Transmission Control Protocol and Internet Protocol
Origin information
Destination information
Sequence information
Data/information/instructions
Packet switching


Break up message into packets, route packets, destination
reassembles the message
Routers direct packets individually along fastest path
52
Network Communications Technologies –
WAP

Wireless Application Protocol
(WAP)


Access Internet via mobile devices
2.0 Specification


Open Mobile Alliance (OMA)
Web sites provide wireless content
to display on microbrowsers

WML – XML application designed for
small screens
53
Network Communications Technologies –
802.11, Bluetooth, IrDA

IEEE 802.11 (802.11b, g – “WiFi”)

Family of standards used with wireless LANs


Bluetooth


Devices contain special chip
Short-range radio waves transmit between Bluetooth devices


Used for public Internet access points
Short distance
IrDA



IrDA devices contain IrDA ports
Infrared light waves
Line-of-sight transmission
54
With TCP/IP is used to send data over the
Internet, the data is divided into small
pieces or ______.
25%
45
25%
bs
hu
to
k
en
s
s
ck
et
4.
pa
3.
nd
le
s
2.
25%
bundles
packets
tokens
hubs
bu
1.
25%
55
Networks –
Intranets

Intranet

Internal network in an organization used to share
information



Enterprise network
Connects to the Internet


Uses Internet technologies (TCP/IP, Web server, Web pages)
Extranet - Allows outside user access
Firewall

Designed to prevent unauthorized access to a private network



Firewall blocks messages that do not meet security criteria
Uses hardware, software, combination of both
All messages entering or leaving the intranet must pass through
the firewall
56
Networks
Extranet is shared content accessed by groups through cross-enterprise boundaries.
Internet is global communication accessed through the Web.
Intranet is shared content accessed by members within a single organization.
57
Networks –
Home Area Networks (HAN)

Network within a home

Connects digital devices
HomePLC – electrical lines; cables
connect card/USB/parallel port to wall
outlet
Phoneline – telephone lines; cables
connect NIC/PC card to telephone jack

Network card that plugs into
PCI slot and wall outlet for
home power-line network
Howstuffworks.com
HomeRF, 802.11b – radio waves; NIC connects to transceiver with
antenna or to wireless access point
Ethernet – twisted pair cables; Ethernet NIC cards and cables to
connect devices

58
Do you have a home area
network?
o
50%
N
s
2.
Yes
No
50%
Ye
1.
30
59
Networks Summary


Uses of Communications Technology
Networks


Communications Devices
Communications Channels


Geographic



Bus, Ring, Star
Protocols


Peer-to-Peer, Client/Server
Topologies


LAN, MAN, WAN
Architectures


Physical and Wireless Transmission Media
Ethernet, Token Ring, TCP/IP, WAP, 802.11, others
Intranets and Firewalls
Home Networks
60