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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.

    3

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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

    4

    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

    5

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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:

    6

    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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    http://www.wisegeek.org/what-is-a-transmission.htmhttp://www.wisegeek.org/what-is-bandwidth.htmhttp://www.wisegeek.org/what-is-bandwidth.htmhttp://www.wisegeek.org/what-is-a-transmission.htm
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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

    14

    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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    http://compnetworking.about.com/od/wireless80211/g/decibel_db.htmhttp://compnetworking.about.com/od/wireless80211/g/decibel_db.htm
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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.

    22

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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