Network Fundamentals

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Network Fundamentals

• Terminology
• Topologies
• Types of Networks
• OSI model
• TCP/IP Concepts
• Types of Networks
• By
• Adwoa Afful (Mrs)

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Networking Terminology
End-user devices provide users with a connection
to the network. Also referred to as hosts.
Allow users to share, create, and obtain
information.
Network devices provide transport for data
between end-user devices. Provide cable
connections, extensions, concentration.
Conversion of data formats, and management of
data transfers
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Physical Topologies

• Physical topology is the actual layout of the
  wire or media
• Examples are Bus, Ring, Star, Extended Star,
  Tree and Mesh toplolgy

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Structure
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Logical Topology

• Logical topology defines how media is accessed
  by hosts

• Broadcast means that each host sends its data to
  all other hosts on the network medium.
• Non-deterministic - there is no order that the
  stations must follow to use the network. First
  come, first served.
• Example

Ethernet

• Token Passing controls network access by passing
  an electronic token sequentially to each host.
• When a host receives the token, that host can
  send data on the network.
• If the host has no data to send, it passes the
  token to the next host and the process repeats
  itself.
• Examples

Token Ring, FDDI
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• LAN
• MAN
• WAN
• SAN
• VPN

• Operate within limited geographical area
• Allow multi-access to high bandwidth media
• Control network privately under local
  administration
• Provide full-time connectivity to local services
• Connect physically adjacent devices
• Spans a metropolitan area such as a city or
  suburban area
• Usually consists of LANs in a common geographic
  area
• Example a bank with multiple branches may
  utilize a MAN
• Operate over a large geographical area
• Allow access over serial interfaces operating at
  lower speeds
• Provide full-time and part-time connectivity
• Connect devices separated over wide areas
• High-performance network to move data to/from
  storage areas
• Separate, dedicated network avoids traffic
  conflict
• Private network constructed within public
  network such as Internet

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Types of VPN

• The following are the three main types of VPNs
• Access VPNs provide remote access for mobile and
  small office, home office (SOHO) users to an
  Intranet or Extranet over a shared
  infrastructure.
• Access VPNs use analog, dialup, ISDN, DSL, mobile
  IP, and cable technologies to securely connect
  mobile users, telecommuters, and branch offices.
• Intranet VPNs use dedicated connections to link
  regional and remote offices to an internal
  network over a shared infrastructure.
• Intranet VPNs differ from Extranet VPNs in that
  they allow access only to the employees of the
  enterprise.

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Contd

• Extranet VPNs use dedicated connections to link
  business partners to an internal network over a
  shared infrastructure.
• Extranet VPNs differ from Intranet VPNs in that
  they allow access to users outside the
  enterprise.

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Bandwidth

• Bandwidth is limited by physics and technology
• Bandwidth is not free
• Bandwidth requirements are growing at a rapid
  rate
• Bandwidth is critical to network performance

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Contd

• Bandwidth is defined as the amount of information
  that can flow through a network connection in a
  given period of time. It is important to
  understand the concept of bandwidth for the
  following reasons

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FINITE

• Bandwidth is finite. Regardless of the media used
  to build a network, there are limits on the
  network capacity to carry information. Bandwidth
  is limited by the laws of physics and by the
  technologies used to place information on the
  media.
• For example, the bandwidth of a conventional
  modem is limited to about 56 kbps by both the
  physical properties of twisted-pair phone wires
  and by modem technology. DSL uses the same
  twisted-pair phone wires.

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Contd

• However, DSL provides much more bandwidth than
  conventional modems. So, even the limits imposed
  by the laws of physics are sometimes difficult to
  define.
• Optical fiber has the physical potential to
  provide virtually limitless bandwidth. Even so,
  the bandwidth of optical fiber cannot be fully
  realized until technologies are developed to take
  full advantage of its potential.

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NOT Free

• Bandwidth is not free. It is possible to buy
  equipment for a LAN that will provide nearly
  unlimited bandwidth over a long period of time.
  For WAN connections, it is usually necessary to
  buy bandwidth from a service provider.
• In either case, individual users and businesses
  can save a lot of money if they understand
  bandwidth and how the demand will change over
  time.

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Contd

• A network manager needs to make the right
  decisions about the kinds of equipment and
  services to buy.
• Bandwidth is an important factor that is used to
  analyze network performance, design new networks,
  and understand the Internet.

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Contd

• A networking professional must understand the
  tremendous impact of bandwidth and throughput on
  network performance and design. Information flows
  as a string of bits from computer to computer
  throughout the world.
• These bits represent massive amounts of
  information flowing back and forth across the
  globe in seconds or less.

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Contd

• The demand for bandwidth continues to grow. As
  soon as new network technologies and
  infrastructures are built to provide greater
  bandwidth, new applications are created to take
  advantage of the greater capacity. The delivery
  of rich media content such as streaming video and
  audio over a network requires tremendous amounts
  of bandwidth.

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Contd

• IP telephony systems are now commonly installed
  in place of traditional voice systems, which
  further adds to the need for bandwidth.
• The successful networking professional must
  anticipate the need for increased bandwidth and
  act accordingly.

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Digital versus analog

• Radio, television, and telephone transmissions
  have, until recently, been sent through the air
  and over wires using electromagnetic waves.
• These waves are called analog because they have
  the same shapes as the light and sound waves
  produced by the transmitters.

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Contd

• As light and sound waves change size and shape,
  the electrical signal that carries the
  transmission changes proportionately.
• In other words, the electromagnetic waves are
  analogous to the light and sound waves

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Analog Measurements

• Analog bandwidth is measured by how much of the
  electromagnetic spectrum is occupied by each
  signal.
• The basic unit of analog bandwidth is hertz (Hz),
  or cycles per second. Typically, multiples of
  this basic unit of analog bandwidth are used,
  just as with digital bandwidth.

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Contd

• Units of measurement that are commonly seen are
  kilohertz (KHz), megahertz (MHz), and gigahertz
  (GHz). These are the units used to describe the
  frequency of cordless telephones, which usually
  operate at either 900 MHz or 2.4 GHz.
• These are also the units used to describe the
  frequencies of 802.11a and 802.11b wireless
  networks, which operate at 5 GHz and 2.4 GHz.

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Contd

• While analog signals are capable of carrying a
  variety of information, they have some
  significant disadvantages in comparison to
  digital transmissions.
• The analog video signal that requires a wide
  frequency range for transmission cannot be
  squeezed into a smaller band. Therefore, if the
  necessary analog bandwidth is not available, the
  signal cannot be sent.

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Contd

• In digital signaling all information is sent as
  bits, regardless of the kind of information it
  is. Voice, video, and data all become streams of
  bits when they are prepared for transmission over
  digital media.
• This type of transmission gives digital bandwidth
  an important advantage over analog bandwidth.

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Contd

• Unlimited amounts of information can be sent over
  the smallest or lowest bandwidth digital channel.
  Regardless of how long it takes for the digital
  information to arrive at its destination and be
  reassembled, it can be viewed, listened to, read,
  or processed in its original form.

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Throughput
Throughput refers to actual measured bandwidth,
at a specific time of day, using specific
Internet routes, and while a specific set of data
is transmitted on the network. Often far less
than the maximum possible digital bandwidth.

• Factors that determine throughput
• Internetworking devices
• Type of data being transferred
• Network topology
• Number of users on the network
• User computer
• Server computer
• Power conditions

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TCP/IP Description

• TCP/IP is a set of protocols developed to allow
  computers to share resources
• TCP/IP can be configured using the operating
  system tools

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Contd

• TCP/IP is a set of protocols or rules that have
  been developed to allow computers to share
  resources across a network.
• The operating system tools must be used to
  configure TCP/IP on a workstation. The process is
  very similar for Windows or Mac operating
  systems.

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Networking Models

• The historical and technical standard of the
  Internet is the TCP/IP model
• The U.S. Department of Defence created the TCP/IP
  reference model, to design a network that could
  survive any conditions, including a nuclear war

• Application layer handles issues of
  representation, encoding, and dialog control.
• Transport layer deals with the quality of
  service issues of reliability, flow control, and
  error correction
• Internet layer is to divide TCP segments into
  packets and send them from any network. Best path
  determination and packet switching occur at this
  layer
• Network Access layer (aka host-to-network layer)
  concerned with all components, both physical and
  logical, that are required to make a physical
  link

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Why a Layered Network Model

• Reduces complexity
• Standardizes interfaces
• Facilitates modular engineering
• Ensures interoperable technology
• Accelerates evolution
• Simplifies teaching and learning

• The OSI reference model was released in 1984 to
  help network builders implement networks that
  could communicate (interoperability)
• The OSI reference model is the primary model for
  network communications
• The process of moving information between
  computers is divided into seven smaller and more
  manageable steps

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Source
Destination
DATA
Application
Application
Presentation
Presentation
DECAPSULATION
Session
Session
ENCAPSULATION
SEGMENT
Transport
Transport
PACKET
Network
Network
FRAME
Data-Link
Data-Link
BITS
Physical
Physical
0101010101010101010
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OSI Top 3 Layers Application issues

• Application
• provides network services to the user's
  applications
• file, print, message, database and application
  services
• HTTP, SMTP, FTP
• Presentation
• responsible for manipulating datas appearance as
  needed by the Application layer
• Data encryption, compression and translation
  services
• JPEG, MIDI, QuickTime, EBCDIC to ASCII
• Session
• establish and maintain communication between two
  hosts
• Dialogue control
• NFS, SQL, RPC, X Window

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OSI Lower 4 Layers Data Transport issues

• Transport
• PDU Segment
• the transport layer establishes, maintains, and
  tears down virtual circuits
• Windowing
• TCP and UDP
• Network
• PDU - Packet
• Routing
• Data packets and route update packets
• connectivity and path selection between two hosts
• Data-Link
• PDU - Frame
• Ethernet LCC and MAC layers
• physical addressing, network topology, network
  access, error notification, ordered delivery of
  frames, and flow control
• Physical
• PDU bits
• Cabling, standards