fn211_chapter_1_-_2
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CHAPTER 1
INTRODUCTION TO NETWORKINGPrinciples Of Communication
ETHERNET Network (LAN)
Improved by W.N.Wahidah
Dec20131
Department of Information and
Communication Technology
DIPLOMA IN INFORMATION TECHNOLOGY(NETWORKING)
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Data Communications Data communications are the exchange of data between two
devices via some form of transmission medium such as wire
cable.
The effectiveness of data communications system depends on
four fundamental characteristics:
1. Delivery. The system must deliver data to the correct destination.
Data must be received by the intended device or user and only bythat device or user.
2. Accuracy. The system must deliver data accurately. Data that
have been altered in transmission and left uncorrected are
unusable.
3. Timeliness. The system must deliver data in timely manner. Data
delivered late are useless.2
DATA
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COMPONENTS
Messageinformation/data to be communicated. Consist of text,
numbers, pictures, sound or video. Senderdevice that sends the data message. Can be computer,
workstation, telephone, video etc.
Receiverdevice that receives the message. Can be computer,workstation, telephone, video etc.
Mediumphysical path which a message travels from sender to
receiver, wired or wireless. Example of wired medium include : twisted-pair wire, coaxial cable, fiber optic cable, and wireless medium such asra
dio waves.
Protocolset of rules that governs data communication. Representagreement between communicating devices.
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1. Communication devicesi. wired devices eg data terminal equipment (DTE), data circuit-terminating
equipment (DCE);
ii. wireless devices eg 3G, GPRS, mobile phone, laptop, netbook
2. Data elementsi. encapsulationeg frames, packets, datagrams;
ii. addresses; sequence numbers
3. Electronic communication methodsExample: simplex, duplex, half-duplex communication, parallel, universal serial
bus, serial, infra red,
Bluetooth, WiFi, 3G
4. Transmission mediumExample: coaxial, optical fibre, unshielded twisted pair (UTP), shielded twisted pair
(STP), infrared,
radio, microwave, satellite
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emen s o a a ommun ca onSystems
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emen s o a a ommun ca onSystems
Communication devices
wired devices eg data terminal equipment (DTE), data circuit-terminatingequipment (DCE);
wireless devices eg 3G, GPRS, mobile phone, laptop, netbook
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Concepts:
a) Analog and Digital Signaling
Data moves in the form of electromagnetic signals across atransmission medium.
Data can be analog or digital.
Analog data refers to information that is continuous; Example:
Digital data refers to information that has discrete states. Example:
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Analog signal Digital signal
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b) Data modulation
i. Modulation is the technique by which data is turned into an analog
wave or a digital signal.
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A computer with an online or Internet connection that connects over a
regular analogphone line includes a modem. This term is derived by combining
beginning letters from the words modulator and demodulator.
In a modem, the modulation process involves the conversion of the digital computersignals (high and low, or logic 1 and 0 states) to analog audio-frequency (AF)tones.
A mechanism that accepts a sequence of data bits and applies modulation to a
carrier wave according to the bits is called a modulator
A mechanism that accepts a modulated carrier wave and recreates the sequence of
data bits that was used to modulate the carrier is called a demodulator
http://searchcio-midmarket.techtarget.com/definition/analoghttp://searchmobilecomputing.techtarget.com/definition/modemhttp://searchmobilecomputing.techtarget.com/definition/modemhttp://searchcio-midmarket.techtarget.com/definition/analog -
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SIMPLEX
The communication
is unidirectional asa one-way street.
HALF-DUPLEX
Each station can both transmit and
receive, but notat the same time.
It is like a one-lane road with trafficallowed in both directions.
Example: the walkie-talkie systems.
c) Simplex, half-duplex, and full-duplex transmission
FULL-DUPLEX
Both stations can transmit and receive data
simultaneously. It is like a two-way street withtraffic flowing in both directions at the same
time.
Example: Telephone network. When two people
are communicating by a telephone line, both
can talk and listen at the same time.
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d) Multiplexing
Multiplexing is the process of transmitting several
different signals or information streams via a single
carrier. The transmissionof all these signals or streams takes
place simultaneously by combining the several signals
into one common signal that will efficiently moves
through the carrier bandwidth.
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e) Point-to-point transmission
f) Broadcast transmissionIn broadcasting communication, the relationship between the
source and the destination is ONE-TO-ALL. There is only one
source but all the other hosts are the destinations.
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Point-to-point provides a dedicated link between two devices. The
entire capacity of the link is reserved for transmission between
those two devices.
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g) Bluetooth and 3G Bluetooth technology is a short-range wireless
communications technology intended to replace
the cables connecting many different types of
devices, from mobile phones and headsets toheart monitors and medical equipment.
The key features of Bluetooth technology are
robustness, low power, and low cost. The Bluetooth
Specification defines a uniform structure for a wide
range of devices to connect and communicate with
each other. When two Bluetooth enabled devices connect to
each other, this is called pairing. The structure and
the global acceptance of Bluetooth technology means
any Bluetooth enabled device, almost everywhere in
the world, can connect to other Bluetooth enabled
devices located in proximity to one another.
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3G, short for third Generation, is the third generation of mobile
telecommunications technology.
3G technologygenerally refers to the standard of accessibility and speed of
mobile devices. It was first used in Japan in the year 2001. The standards of
the technology were set by the International Telecommunication Union (ITU).
This technology enables use of various services like GPS (Global Positioning
System), mobile television and video conferencing. It not only enables them to
be used worldwide, but also provides with better bandwidth and increasedspeed. 4G ?
http://www.engineersgarage.com/articles/what-is-3g-technology-specificationshttp://www.engineersgarage.com/articles/global-positioning-system-gpshttp://www.engineersgarage.com/articles/global-positioning-system-gpshttp://www.engineersgarage.com/articles/video-conferencinghttp://www.engineersgarage.com/articles/video-conferencinghttp://www.engineersgarage.com/articles/global-positioning-system-gpshttp://www.engineersgarage.com/articles/global-positioning-system-gpshttp://www.engineersgarage.com/articles/what-is-3g-technology-specifications -
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h) ThroughputNetwork Throughput refers to the volume of data that can flow
through a network. Network Throughput is constrained by
factors such as the network protocols used, the capabilities of
routers and switches, and the type of cabling, such asEthernet and fiber optic, used to create a network.
In communication networks, such as Ethernet or packet radio,
throughput or network throughput is the average rate of
successful message delivery over a communication
channel.This data may be delivered over a physical or
logical link, or pass through a certain network node. The
throughput is usually measured in bits per second (bit/s or
bps), and sometimes in data packets per second or data
packets per time slot.
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i) BandwidthBandwidth describes the maximum data transfer rateof
a networkor Internetconnection. It measures how
much data can be sent over a specific connection in
a given amount of time.
For example, a gigabit Ethernetconnection has abandwidth of 1,000 Mbps, (125 megabytes per
second). An Internet connection via cable
modemmay provide 25 Mbps of bandwidth.
A link may have a bandwidth of B bps, but we can only
send T bps through this link with T always less than B.(T
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Transmission Flaws
Signals travel through transmission media, whichare not perfect. The signal at the beginning of the
medium is not the same as the signal at the end of
the medium. The causes of the flaws or impairment
are: NOISE and ATTENUATION
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NOISE
There are several types of noise, such as
thermal noise, induced noise, crosstalk,
and impulse noise which, may corrupt the
signal.
1. Thermal noise : The random motion ofelectrons in a wire which creates an extra
signal not originally sent by the
transmitter.
2. Induced noise : It comes from sourcessuch as motors and appliances. These
devices act as a sending antenna, andthe transmission medium acts as a
receiving antenna.
3. Crosstalk: It is the effect of one wire onthe other. One wire acts as a sending
antenna and the other as the receiving
antenna.4. Impulse noise : It is a spike (a signal
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Noise can be defined as an unwanted signal that interferes with the communication or
measurement of another signal. A noise itself is a signal that conveys information regarding
the source of the noise. For example, the noise from a car engine conveys informationregarding the state of the engine.
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ATTENUATIONAttenuation is a loss of signal strength measured
in decibels (dB). It also means a loss of energy.
When a signal travels through a medium, it loses
some of its energy in overcoming the resistance
of the medium. That is why a wire carrying
electric signals gets warm after a while.
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RULES OF COMMUNICATION In any conversation between two people, there are
many rules, or protocols, that the two must follow inorder for the message to be successfully deliveredand understood.
Among the protocols for successful humancommunication are: Identification of sender and receiver
Agreed-upon medium or channel (face-to-face,telephone, letter, photograph)
Appropriate communication mode (spoken, written,illustrated, interactive or one-way)
Common language
Grammar and sentence structure
Speed and timing of delivery
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RULES OF COMMUNICATION
Protocols are specific to the characteristics of the source,
channel and destination of the message. The rules used to communicate over one medium, like a
telephone call, are not necessarily the same ascommunication using another medium, such as a letter.
Protocols define the details of how the message istransmitted, and delivered. This includes issues of:
Message format
Message size
Timing
Encapsulation Encoding
Standard message pattern
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RULES OF COMMUNICATION
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RULES OF COMMUNICATION(1) Message Encoding
Encoding - process of converting thoughts into the language,symbols, or sounds, for transmission.
Decoding - reverses this process in order to interpret the thought.
Encoding between hosts must be in an appropriate form for the
medium.
Messages sent across the network are first converted into bits bythe sending host.
Each bit is encoded into a pattern of sounds, light waves, or
electrical impulses depending on the network media over which
the bits are transmitted.
The destination host receives and decodes the signals in order tointerpret the message.
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RULES OF COMMUNICATION(2) Message Formatting
Depend on the type of message and the channel that is usedto deliver the message.
Each computer message is encapsulated in a specific format,called a frame, before it is sent over the network.
Frame - provides the address of the intended destination andthe address of the source host.
The format and contents of a frame are determined by thetype of message being sent and the channel over which it iscommunicated.
Messages that are not correctly formatted are notsuccessfully delivered to or processed by the destinationhost.
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RULES OF COMMUNICATION
(2) Message Formatting
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RULES OF COMMUNICATION
- ACTIVITY(2) Message Formatting
Place the components of the following voice message into
the proper location within a frame. Mizi calls his friend
Yanti and leaves her a voice message about their
homework assignment.
Yanti tel no: 012 345 6789
Mizi tel no: 012 987 6543
Voice message: Hi Yanti. Can you help me on question
number 2? Thank you.
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RULES OF COMMUNICATION
(3) Message Size When a long message is sent from one host to another
over a network, it is necessary to break the message
into smaller pieces.
The rules that govern the size of the pieces, or frames,
communicated across the network are very strict.
They can also be different, depending on the channel
used.
Frames that are too long or too short are not delivered.
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RULES OF COMMUNICATION
(3) Message Size The size restrictions of frames require the source host to
break a long message into individual pieces that meet
both the minimum and maximum size requirements.
Each piece is encapsulated in a separate frame with the
address information, and is sent over the network.
At the receiving host, the messages are de-
encapsulated and put back together to be processed
and interpreted.
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RULES OF COMMUNICATION
(4) Message TimingAccess method
Determines when is able to send a message.
Based on the environment.
Hosts on a network need an access method to know when to
begin sending messages and how to respond when errors occur.
Flow control
How much information can be sent and the speed that it can be
delivered.
A sending host can transmit messages at a faster rate than thedestination host can receive and process.
Source and destination hosts use flow control to negotiate correct
timing for successful communication.
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RULES OF COMMUNICATION
(4) Message Timing Response timeout
Hosts on the network also have rules that specify how long to
wait for responses and what action to take if a response timeout
occurs.
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RULES OF COMMUNICATION
(5) Message Patterns Unicast
A one-to-one message pattern.
There is only a single destination for the message.
Multicast
A host needs to send messages using a one-to-many pattern.
Delivery of the same message to a group of host destinations
simultaneously.
Broadcast
All hosts on the network need to receive the message at thesame time.
Represents a one-to-all message pattern.
Hosts have requirements for acknowledged versus
unacknowledged messages.
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RULES OF COMMUNICATION(6) Message Patterns
Protocol use in communication
All communication, both human and computer, is governed by
pre-established rules, or protocols.
These protocols are determined by the characteristics of the
source, channel and destination. Based on the source, channel and destination, the protocols
define the details for the issues of message format, message
size, timing, encapsulation, encoding and standard message
pattern.
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RULES OF COMMUNICATION
- ACTIVITY Determine if the communication problem described
deals with message format, timing, message pattern
or message size.
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IMPORTANCE OF PROTOCOLS
Computers use rules, or protocols, in order tocommunicate.
In a wired environment, a local network is defined
as an area where all hosts must "speak the same
language" or in computer terms "share a commonprotocol".
If devices in a local network did not use the same
protocols they would not be able to communicate.
Ethernet - The most common set of protocols
used on local wired networks.
The Ethernet protocol defines many aspects of
communication over the local network, including:30
STANDARDIZATION OF
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STANDARDIZATION OF
PROTOCOL
As networks became more widespread,standards were developed that defined rules by
which network equipment from different vendors
operated.
Standards are beneficial to networking in manyways:
Facilitate design
Simplify product development
Promote competition
Provide consistent interconnections
Facilitate training
Provide more vendor choices for customers31
STANDARDIZATION OF
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STANDARDIZATION OF
PROTOCOL
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STANDARDIZATION OF
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STANDARDIZATION OF
PROTOCOL
IEEE The Institute of Electrical and Electronic Engineers
Maintains the networking standards, including
Ethernet and wireless standards.
Responsible for approving and maintaining thestandards for connections, media requirements and
communications protocols.
Each technology standard is assigned a number
that refers to the committee that is responsible forapproving and maintaining the standard.
Eg:
Ethernet standards is 802.3.
100BASE-T33
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Local Area Network (LAN)
ETHERNET Network
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PHYSICAL ADDRESSING
For identifying source and destination hosts. Every Ethernet network interface has a physical
address assigned to it - Media Access Control
(MAC) address.
The MAC address identifies each source and
destination host on the network.
Ethernet network
Are cable based, meaning that a copper or fiberoptic cable connects hosts and networking devices.
This is the channel used for communications
between the hosts.
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PHYSICAL ADDRESSING
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ETHERNET COMMUNICATION
When messages are sent between hosts on anEthernet network, the hosts format the messages
into the frame layout that is specified by the
standards.
Frames, also referred to as Protocol Data Units(PDUs).
The format for Ethernet frames specifies the
location of the destination and source MAC
addresses, and additional information including:
Preamble for sequencing and timing
Start of frame delimiter / Frame Header Section
Length and type of frame / Data Section
Frame Check Se uence FCS to detect37
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ETHERNET COMMUNICATION
Preamble Defined pattern of alternating 1 and 0 bits used to
synchronize timing.
Frame Header Section
Marks the end of the timing information and start ofthe frame.
Destination MAC Address
Contains the destination MAC address (receiver).
Can be unicast, multicast or broadcast.38
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ETHERNET COMMUNICATION
Source MAC Address Contains the source MAC address (sender).
This is the unicast address of the Ethernet node
that transmitted the frame.
Length / Type Support two different uses.
Type - indicates which protocol will receive the data.
Length - indicates the number of bytes of data that
follows this field.39
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ETHERNET COMMUNICATION
Encapsulated Data Contains the packet of information being sent.
Ethernet requires each frame to be between 64 and
1518 bytes.
Frame Check Sequence Contains 4-byte value that is created by the device
that sends data and is recalculated by the
destination device to check for damaged frames.
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ETHERNET COMMUNICATION
Build a standard IEEE 802.3 Ethernet frame baseon the source and the destination device.
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HIERARCHICAL ETHERNET
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HIERARCHICAL ETHERNET
NETWORK DESIGN
Access layer Distribution layer
Core layer
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LOGICAL ADDRESS
Physical address It is physically assigned to the host NIC
MAC address does not change
IP address/network address
Also known as logical address
Assigned to each host by a network administrator
based on the local network, where the host is
located.
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LOGICAL ADDRESS
IP addresses contain two parts:(1) Identifies the local network.
The network portion of the IP address will be the same for
all hosts connected to the same local network.
(2) Identifies the individual host. Within the same local network, the host portion of the IP
address is unique to each host.
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To be continue
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