POLITEKNIK MALAYSIA

CHAPTER 3: DATACHAPTER 3: DATA
TRANSMISSION &TRANSMISSION &
NETWORKING MEDIANETWORKING MEDIA

DATATRANSMISSIONDATATRANSMISSION

Transmission BasicsTransmission Basics
Transmission has two meanings:
◦ Refers to process of issuing data signals on a medium
◦ Refers to progress of data signals over a medium
On a data network, information can be
transmitted via one of two methods:
◦ Analog
◦ Digital

Transmission BasicsTransmission Basics
Both analog and digital signals are generated
by electrical current, pressure of which is
measured in volts
In analog signals, voltage varies continuously
In digital signals, voltage turns off and on
repeatedly

 Electronic signal that varies directly with time
changes for an infinite range of time. (
 Your speech, a siren, and live music are all examples
of analog waves.
 using of continuous signals to represent
information/data.
 An analog signal is characterized by four fundamental
properties: amplitude, frequency, wavelength, and
phase.
Analog Signaling

 amplitude is a measure of its strength at any given
point in time.)
 frequency is a number of wave cycles in one second
(f=1/t). t=The times of wave’s amplitude cycles from
its starting point, through its highest amplitude and
its lowest amplitude.
 Wavelength is a distance between corresponding
points on a wave’s cycle
 phase refers to the change or movement of the
signal in the form of angle.
Analog Signaling…Cont…

amplitude frequency
wavelength
phase

 Digital signals are composed of pulses of precise,
positive voltages and zero voltages.
 A pulse of positive voltage represents a 1.A pulse of
zero voltage represents a 0.
 Every pulse in the digital signal is called a binary digit,
or bit.
 A bit can have only one of two possible values: 1 or
0. Eight bits together form a byte.
Digital Signaling

 using of discrete signals to represent
information/data.
 Number, letters or icons are all examples of digital
signal.
 Advantage:
◦ more reliable than analog transmission
◦ noise affects digital transmission less severely
Digital Signaling…Cont

Differences between analog & Digital
 Analog signals are continuous where digital signals
are discrete
 TV, some telephones, and tape recorders all use
analog signals while the digital signal is numbers,
letters or icons

NETWORKING MEDIANETWORKING MEDIA
a. Throughput
b. Noise immunity
c. Size and scalability
d. Cost

TRANSMISSION MEDIATRANSMISSION MEDIA

 Twisted-pair cable consists of color-coded pairs of
insulated copper wires.
 Every two wires are twisted around each other to
form pairs and all the pairs are encased in a plastic
sheath.
 The more twists per inch in a pair of wires, the more
resistant the pair will be to crosstalk.
 It is relatively inexpensive, flexible, and easy to install.
 Twisted-pair cable falls into one of two categories:
STP (shielded twisted-pair) or UTP (unshielded
twisted-pair)
Twisted Pair Cable

Common Network CablesCommon Network Cables
Twisted Pair is used for Ethernet

 surrounded by a shielding made of a metallic
substance such as foil.
 The shielding acts as a barrier to external
electromagnetic forces, thus preventing them from
affecting the signals traveling over the wire inside the
shielding
Twisted Pair Cable… STP (Shielded Twisted-Pair)

 UTP does not contain additional shielding for the twisted
pairs.
 Only consists of one or more insulated wire pairs
encased in a plastic sheath.
Twisted Pair Cable… UTP (Unshielded Twisted-Pair)

Unshielded twisted pair (UTP) is the most commonly
encountered type of network cable in North America
to connect hosts, workstations, and other networking
devices

 Throughput—STP and UTP can both transmit data
at 10, 100, and 1000 Mbps (1Gbps), depending on the
grade of cabling and the transmission method in use.
 Cost—STP is more expensive than UTP because it
contains more materials and it has a lower demand.
 Connector—STP and UTP use RJ-45 (Registered
Jack 45) and RJ-11 (Registered Jack 11).

 Noise immunity—Because of its shielding, STP is
more noise-resistant than UTP. (disebabkan ia mengandungi pelindung, STP
lebih tahan hingar(noise) daripada UTP)
 Size and scalability—The maximum segment length
for both STP and UTP is 100 m, or 328 feet. (Panjang
maksimum segmen bagi kedua-dua STP dan UTP adalah 100 m, atau 328 kaki)

 CAT 5e (Enhanced Category 5)—A higher-grade
version of CAT 5 wiring that contains high-quality
copper, offers a high twist ratio, and uses advanced
methods for reducing crosstalk. Enhanced CAT 5 can
support a signaling rate as high as 350 MHz, more than
triple the capability of regular CAT 5.
 CAT 6 (Category 6)—A twisted-pair cable that
contains four wire pairs, each wrapped in foil
insulation.Additional foil insulation covers the bundle
of wire pairs, and a fire-resistant plastic sheath covers
the second foil layer.The foil insulation provides
excellent resistance to crosstalk and enables CAT 6 to
support a 250-MHz signaling rate and at least six
times the throughput supported by regular CAT 5.

version of CAT 6 wiring that reduces attenuation and
crosstalk, and allows for potentially exceeding
traditional network segment length limits. CAT 6e is
capable of a 550 MHz signaling rate and can reliably
transmit data at multi-Gigabit per second rates.
contains multiple wire pairs, each surrounded by its
own shielding, then packaged in additional shielding
beneath the sheath. CAT 7 cabling is that it can
support signal rates up to 1 GHz.

version of CAT 5 wiring that contains high-quality copper,
offers a high twist ratio, and uses advanced methods for
reducing crosstalk. Enhanced CAT 5 can support a
signaling rate as high as 350 MHz, more than triple the
capability of regular CAT 5.
contains four wire pairs, each wrapped in foil insulation.
Additional foil insulation covers the bundle of wire pairs,
and a fire-resistant plastic sheath covers the second foil
layer.The foil insulation provides excellent resistance to
crosstalk and enables CAT 6 to support a 250-MHz
signaling rate and at least six times the throughput
supported by regular CAT 5.

 Coaxial cable consists of a central copper core
surrounded by an insulator, a braided metal shielding,
called braiding, and an outer cover, called the
sheath or jacket.
 The core carries the electromagnetic signal, and the
braided metal shielding acts as both a shield against
noise.
 all types have been assigned an RG (radio guide)
specification number.
Coaxial cable

Provides improved shielding compared to UTP, so
has a lower signal-to-noise ratio
More difficult to install
Coaxial cable

Coaxial cable
Coaxial cable F-Type connector

 Have two categories: Thicknet and Thinnet.
 Thicknet
◦ Its diameter is approximately 1 cm
◦ IEEE has designated Thinnet as 10BASE-5 Ethernet
◦ maximum segment length are 500 meters.
 Thinnet
◦ Its diameter is approximately 0.64 cm
◦ IEEE has designated Thinnet as 10BASE-2 Ethernet
◦ maximum segment length are 185 meters (or roughly 200)
Coaxial cable…

 Fiber-optic cable, or simply fiber, contains one or
several glass or plastic fibers at its center, or core.
 Surrounding the fibers is a layer of glass or plastic
called cladding.
 Outside the cladding, a plastic buffer protects the
cladding and core.
Fiber-optic Cable

Provides improved shielding compared to UTP, so has a
lower signal-to-noise ratio and can therefore carry more
data
Used in enterprise environments and large data centers
Fiber-optic Cable

Fiber-optic Cable
 Many extremely thin
strands of glass or plastic
bound together in a
sheathing which transmits
signals with light beams
 Can be used for voice, data,
and video
Fiber-optic Cable

 To prevent the cable from stretching, and to protect
the inner core further, strands of Kevlar (an
advanced polymeric fiber) surround the plastic buffer.
 Finally, a plastic sheath covers/outer jacket the
strands of Kevlar.
 Have two categories: single-mode and multimode.
Fiber-optic Cable

 SMF (single-mode fiber) uses a narrow core (less
than 10 microns in diameter) through which light
generated by a laser travels over one path, reflecting
very little.
 Because it reflects little, the light does not disperse
as the signal travels along the fiber.
 accommodate high bandwidths and long distances.
Fiber-optic Cable…SMF (Single-Mode Fiber)

 MMF (multimode fiber) contains a core with a
larger diameter than single-mode fiber (between 50
and 115 microns in diameter; the most common size
is 62.5 microns) over which many pulses of light
generated by a laser or LED travel at different angles.
 It is commonly found on cables that connect a router
to a switch or a server on the backbone of a
network.
Fiber-optic Cable…MMF (Multimode Fiber)

Fiber-optic Cable…Connector
(a) ST (Straight Tip) (b) SC (Standard Connector)
(c) LC (Local Connector) (d) MT-RJ (Mechanical Transfer
Registered Jack)

 Throughput—Fiber has proved reliable in
transmitting data at rates that exceed 10 Gigabits (or
10,000 Megabits) per second.
 Cost—Fiber-optic cable is the most expensive
transmission medium.
 Noise immunity—Because fiber does not conduct
electrical current to transmit signals, it is unaffected
by EMI.
 Size and scalability—Depending on the type of
fiber-optic cable used, segment lengths from 150 to
40,000 meters.
Fiber-optic Cable…characteristics

Network CablingNetwork Cabling Some TipsSome Tips
 A straight-thru cable has identical ends.
 A crossover cable has different ends.
 A straight-thru is used as a patch cord in Ethernet
connections.
 A crossover is used to connect two Ethernet devices
without a hub or for connecting two hubs.
 A crossover has one end with the Orange set of wires
switched with the Green set.
 Looking at the RJ-45 with the clip facing away from you,
Brown is always on the right, and pin 1 is on the left.

Straight-through UTP cable
The TIA/EIA 568-A standard which was ratified
in 1995, was replaced by the TIA/EIA 568-B
standard in 2002 and has been updated since.
Both standards define the T-568A and T-568B
pin-outs for using Unshielded Twisted Pair
cable and RJ-45 connectors for Ethernet
connectivity.

GW, G, OW, B, BW, O, BW, B OW, O, GW, B, BW, G, BW, B
Illustration of TIA/EIA 568-A Illustration of TIA/EIA 568-B

Cross-over UTP cable
 If you require a cable to connect two Ethernet
devices directly together without a hub or when
you connect two hubs together, you will need to
use a Crossover cable instead.

BASIC CONCEPT OFBASIC CONCEPT OF
INTERNETINTERNET
CONNECTIONCONNECTION

Internet Service Providers (ISPs)Internet Service Providers (ISPs)
Internet Service Providers
◦ Give users access to internet resources
◦ Allow organizations and individuals to publish
information on the internet

Internet Service Providers (ISP’s)Internet Service Providers (ISP’s)
 ISP is a business or organization that provides
access to Internet and related services to
consumers.
 Mostly, an ISP is a telephone company.
 Telecommunications companies that provide
home or business users with a connection to
the Internet.
 Organisations that provide Internet Services
 Must have a local Point of Presence (PoP)
 Charges and service vary considerably

ISPISP
Two reasons to have one
◦ Dial up to connect to the internet
◦ Web space, email, domain name etc.
Home users these are usually the same ISP
Business Users may not be the same
◦ Different services, different rates

What services?What services?
Connection to The Internet
Email accounts (how many)
Web Space (how much)
Technical Help(free?)
Fixed / varied IP Address
Other Items?

Internet Services (Cont)Internet Services (Cont)
Other facilities they offer such as web page space
and support
◦ Most offer web space
◦ Basic services (restricted /cgi-bin access, and logging if
you’re very lucky).
◦ Dedicated games servers
◦ Web filtering for family usage
◦ Anti-spam protection
◦ Portal-type home pages etc.

Internet ConnectionsInternet Connections
 Internet service provider (ISP) A company that
provides other companies or individuals with access to
the Internet
 There are various technologies available that you can
use to connect a home computer to the Internet
◦ A phone modem converts computer data into an analog
audio signal for transfer over a telephone line, and then a
modem at the destination converts it back again into data
◦ A digital subscriber line (DSL) uses regular copper
phone lines to transfer digital data to and from the phone
company’s central office
◦ A cable modem uses the same line that your cable TV
signals come in on to transfer the data back and forth

15-51
Internet ConnectionsInternet Connections
Broadband A connection in which transfer
speeds are faster than 128 bits per second
◦ DSL connections and cable modems are broadband
connections
◦ The speed for downloads (getting data from the
Internet to your home computer) may not be the
same as uploads (sending data from your home
computer to the Internet)

Explain What the Internet IsExplain What the Internet Is
The Internet is a network of networks that
connects users in every country in the
world.
Users are connected to ISPs
ISPs are connected to other ISPs

The ISPs Relationship With theThe ISPs Relationship With the
InternetInternet
ISPs use a POP to provide service to end
users
There are many POPs in an ISPs network

Options for Connecting to the ISPOptions for Connecting to the ISP
Identify and describe the different
connection options that ISPs can provide

Options for Connecting to the ISPOptions for Connecting to the ISP
Dialup (56 Kb Modem)
Cable
Digital Subscriber Line
Leased Line (T-1)
Satellite
Cell Modem (Air Card)

ISP Levels of ServicesISP Levels of Services
 Various services are available
(see graphic)
 Most ISPs offer two different
contract levels: home service or
business class service.
 Asymmetric
◦ Different upload and
download speeds
◦ Used for home
 Symmetric
◦ Same upload and download
speeds
◦ Used for business

Importance of the Internet Protocol (IP)Importance of the Internet Protocol (IP)
Must run Internet Protocol (IP) software to
communicate on Internet
IP protocol is one of the TCP/IP (Transmission
Control Protocol / Internet Protocol) Protocols
As Ethernet uses Frames, IP uses Packets
Each IP packet must contain a valid source and
destination IP address.

Importance of the Internet ProtocolImportance of the Internet Protocol
(IP)(IP)
The IP Packet (datagram)
• Has a header which
contains the source
and destination IP
addresses
• IP addresses must be
unique on the
Internet.
• Computers in homes,
small businesses and
other organizations
obtain their IP
configuration from
their ISP.

How ISPs Handle PacketsHow ISPs Handle Packets
 Messages are divided into packets – size between 64 to 1500 bytes
for Ethernet
 Downloading a single 1 MB song would require over 600 packets o
1500 bytes.
 Each individual packet must have a source and destination IP
address.
 Packets or datagrams contain IP address and control information
 IP addresses are granted to ISPs from a regional Internet registry
(RIR)
 Internet Assigned Numbers Authority: responsible for IP addressing
 Internet Corporation for Assigned Names and Numbers:
responsible for names and IP addressing

How ISPs Handle PacketsHow ISPs Handle Packets
 NOC controls the flow of traffic
 Sends traffic to remote networks if necessary
 Contains services: e-mail, web

 ping - tests end-to-end connectivity between source and destination
 traceroute - traces the route from source to destination, displays each
router and 3 Round Trip Times (RTT)
 Packets are sent from router to router until they reach their destination
 PACKET TRACER 4.2.3.2
Forwarding Packets Across the Internet

Devices in Internet CloudDevices in Internet Cloud
DSL Access Multiplexer (DSLAM)
Cable Modem Termination System (CMTS)

Physical and Environmental RequirementsPhysical and Environmental Requirements
Physical requirements of a home network versus
an ISP

Protocols are rules that allow computer
systems to connect with different systems to
transfer data.
Protocols are rules
This is important because the Internet
involves many different types of
devices.
And it’s vital as rules are needed for how the
Internet transfers data using packets
packets
Internet ProtocolsInternet Protocols

Together they’re called TCP/IP
IP
All that is controlled by two
protocols that make the Internet
possible:
TCP

Is responsible for breaking data into packets
Then assembling the packets again when
they arrive
Transmission Control Protocol (TCP)Transmission Control Protocol (TCP)

Is responsible for handling the routing of
packets
That’s addressing, sending and receiving packets
over the Internet
Every device on the Internet has a special
numerical address
It is called an IP address
212.58.244.71
4 numbers (up to 255) divided with dots
Internet Protocol (IP)Internet Protocol (IP)

Internet Protocol – IP AddressesInternet Protocol – IP Addresses
• IP addresses can be ‘private’ or ‘public’
• For example, computers on our school
network use private IP addresses because
they only work on our LAN
• IP addresses can also be ‘static’ (permanent)
or ‘dynamic’ (temporary)
• For example, your ISP will give your home
router a temporary IP address
• But today’s networks are smart enough to use
all kinds of IP addresses to deliver packets to
the right devices!
• Without protocols, the Internet would be
chaos!

TCPTCP
IP
TCP
Internet ProtocolInternet Protocol

Packet SwitchingPacket Switching
 To improve the efficiency of transferring information over a
shared communication line, messages are divided into fixed-
sized, numbered packets
 Network devices called routers are used to direct packets
between networks
Figure 15.4
Messages
sent by
packet
switching
15-18

Trace Route (Tracert)Trace Route (Tracert)
Trace Route (tracert) is a command-line diagnostic
utility that is used to determine the route a packet
uses to get to a destination.
Traces a packet from your computer to an
Internet host, showing how many hops the
packet requires to reach the host and how long
each hop takes.
Tracert determines the route by sending Internet
Control Message Protocol (ICMP) packets to the
destination that you specify, either by IP address or
DNS name.

Using Tracert for TroubleshootingUsing Tracert for Troubleshooting
Use tracert to determine where packet traffic is
being stopped.
Tracert can be used to show routers with
configuration problems or that are offline.
It can also indicate that an incorrect IP address is
being used or that a specific network does not exist.
It can also pinpoint bottlenecks in the network.
If you're visiting a Web site and pages are appearing
slowly, you can use trace route to figure out where
the longest delays are occurring.

Tracert ResultTracert Result
Hop 1: my home LAN router
Hops 2: Psmza LAN

PINGPING
Stands for "Packet INternet Groper.“
An Internet utility used to determine
whether a particular IP address is
reachable online by sending out a packet
and waiting for a response.
Ping is used to test and debug a network
as well as see if a user or server is online.

PINGPING
The PING utility is used to see if the TCP/IP protocol is
functioning correctly on a host computer and to check
connectivity between devices.
Like tracert, PING uses the Internet Control Message
Protocol (ICMP) echo function to send a packet through
the network to another host.
If there is a good connection between the hosts, a good
return packet will be received. .
PING can also report the number of router hops
between the two computers and the amount of time it
takes for a packet to make the complete trip.
You can PING a host by DNS name or IP address

Using PING for TroubleshootingUsing PING for Troubleshooting
PING can be used to test a local host or a connection to
another host.
 Always begin by PINGing the local computer, that is, the
computer you are currently using. You can PING the actual
machine IP address, or PING the machine using the local
loopback address of 127.0.0.1.
 Once you determine that the local machine’s IP address is
functioning correctly, PING your default gateway. This will
determine whether or not you have connectivity across your
side of the network.
 Once you can successfully PING the default gateway, PING a
host on the far side of the router. For example, you may
choose to PING a host on another network segment within
your own company or a popular Web site.
PING can also be used to test name resolution services
Syntax: ping IP address or domain

Ping resultsPing results
1. The command to ping www.psmza.edu.my four times
2. The replies took between 5 and 18 milliseconds
3. No packets were lost
4. The average ping time was 10 milliseconds

NslookupNslookup
Nslookup is a program that allows you to directly query
a DNS server by host name or IP address.
lets an Internet server administrator or user enter a
host name (for example, www.yahoo.com) and find
out the corresponding Internet address.
It will also do reverse name lookup and find the host
name for an IP address you specify.

NslookupNslookup
Nslookup sends a domain name query packet
to a designated (or defaulted) Domain Name
System (DNS) server.
Depending on the system you are using, the
default may be the local DNS name server at
your service provider, some intermediate name
server, or the root name server (at InterNIC)
for the entire domain name system hierarchy.
Syntax: nslookup IP address or domain

Nslookup ResultNslookup Result

Nslookup Modes of OperationNslookup Modes of Operation
Interactive mode allows the user to query name servers
for information about various hosts and domains.
◦ Additionally, interactive mode allows you to specify
additional parameters when using nslookup.
◦ Interactive mode is entered automatically when no
arguments are given.
◦ You will know you are using interactive mode by
looking at the command prompt.

Nslookup Modes of OperationNslookup Modes of Operation
(continued)(continued)
Noninteractive or command-line mode
◦ Used to return just the name or other requested
information for a host or domain.
◦ When noninteractive mode is used, you supply the
name or Internet address of the host as an argument.

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