CCNA SEMESTER 1 V 3.0

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CCNA SEMESTER 1 V 3.0

• CHAPTER 2

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Students completing this chapter should be able
to

• Explain the importance of bandwidth in
  networking.
• Use an analogy from their experience to explain
  bandwidth.
• Explain the difference between bandwidth and
  throughput.
• Calculate data transfer rates.
• Explain why layered models are used to describe
  data communication.
• Explain the development of the Open System
  Interconnection model (OSI).
• List the advantages of a layered approach.
• Identify each of the seven layers of the OSI
  model.
• Identify the four layers of the TCP/IP model.
• Describe the similarities and differences between
  the two models.
• Briefly outline the history of networking.
• Identify devices used in networking.
• Understand the role of protocols in networking.
• Define LAN, WAN, MAN, and SAN.
• Explain VPNs and their advantages.
• Describe the differences between intranets and
  extranets.
•     

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Networking Fundamentals
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Evolution of Networking
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Local Area Networks (LAN)

• Businesses needed a
• solution that would
• successfully address the
• following three problems
• How to avoid duplication of equipment and
  resources
• How to communicate efficiently
• How to set up and manage a network

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Wide-area networks (WANs)

• A way for information to move efficiently and
  quickly
• WANs could connect user networks over large
  geographic areas

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Examples of data Networks
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Networking Devices

• Equipment that connects directly to a network
  segment is referred to as a device. These devices
  are broken up into two classifications.
• Network Devices
• end-user devices

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End user devices

• End-user devices that provide users with a
  connection to the network are also referred to as
  hosts
• These devices allow users to share, create, and
  obtain information.
• Host devices are physically connected to the
  network media using a network interface card
  (NIC)

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Network interface card(NIC)

• A NIC is a printed circuit board that fits into
  the expansion slot of a bus on a computer
  motherboard, or it can be a peripheral device.

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Network interface card(NIC)

• Laptop or notebook computer NICs are usually the
  size of a PCMCIA card.
• Each individual NIC carries a unique code, called
  a Media Access Control (MAC) address

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End User Devices
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Network devices

• Network devices provide transport for the data
  that needs to be transferred between end-user
  devices. Network devices provide extension of
  cable connections, concentration of connections,
  conversion of data formats, and management of
  data transfers.

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Network Devices
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Repeater

• A repeater is a network device used to regenerate
  a signal. Repeaters regenerate analog or digital
  signals distorted by transmission loss due to
  attenuation.

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Bridges

• convert network transmission data formats as well
  as perform basic data transmission management.
• provide connections between LANs.
• perform a check on the data to determine whether
  it should cross the bridge or not. This makes
  each part of the network more efficient

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Bridges
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Switches

• Workgroup switches add more intelligence to data
  transfer management.
• They can determine whether data should remain on
  a LAN or not
• They can transfer the data only to the connection
  that needs that data.

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Switches
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Routers

• Routers have all the capabilities listed above.
• regenerate signals
• concentrate multiple connections
• convert data transmission formats, and manage
  data transfers
• They can also connect to a WAN, which allows them
  to connect LANs that are separated by great
  distances

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Network topology

• Network topology defines the structure of the
  network. One part of the topology definition is
  the physical topology, which is the actual layout
  of the wire or media. The other part is the
  logical topology, which defines how the media is
  accessed by the hosts for sending data

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Logical topology

• The logical topology of a network is how the
  hosts communicate across the medium
• - broadcast
• Ethernet
• - token passing
• Token Ring
• Fiber Distributed Data
  Interface (FDDI)

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Different topologies
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A protocol

• A protocol is a formal description of a set of
  rules and conventions that govern a particular
  aspect of how devices on a network communicate.
• Protocols determine the format, timing,
  sequencing, and error control in data
  communication

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Protocols

• Protocols control all aspects of data
• communication, which include the following
• (IEEE, ANSI , TIA , EIA , ITU )
• How the physical network is built
• How computers connect to the network
• How the data is formatted for transmission
• How that data is sent
• How to deal with errors

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Local-area networks (LANs)

• LANs consist of the
• following components
• Computers
• Network interface cards
• Peripheral devices
• Networking media
• Network devices

• Some common LAN
• technologies are
• Ethernet
• Token Ring
• FDDI

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LANs technologies
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Wide-area networks (WANs)

• WANs interconnect LANs, which then provide access
  to computers or file servers in other locations.

• Some common WAN
• technologies are
• Modems
• Integrated Services Digital Network (ISDN)
• Digital Subscriber Line (DSL)
• Frame Relay
• US (T) and Europe (E) Carrier Series T1, E1,
  T3, E3
• Synchronous Optical Network (SONET)

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WANs and WAN Devices
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Metropolitan-area networks (MANs)

• A MAN is a network that spans a metropolitan area
  such as a city or suburban area. A MAN usually
  consists of two or more LANs in a common
  geographic area .

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Storage-area networks (SANs)

• A SAN is a dedicated, high-performance network
  used to
• move data between servers and storage resources
• SANs offer the following features
• Performance SANs enable concurrent access of
  disk or tape arrays by two or more servers at
  high speeds.
• Availability SANs have disaster tolerance built
  in, because data can be mirrored using a SAN up
  to 10 kilometers (km) or 6.2 miles away.
• Scalability Like a LAN/WAN, it can use a
  variety of technologies. This allows easy
  relocation of backup data, operations, file
  migration, and data replication between systems.

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Storage-area networks (SANs)
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Virtual private network (VPN)

• A VPN is a private network that is constructed
  within a public network infrastructure such as
  the global Internet. Using VPN, a telecommuter
  can access the network of the company
  headquarters through the Internet by building a
  secure tunnel between the telecommuters PC and a
  VPN router in the headquarters

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Types of VPNs

• Access VPNs Access VPNs provide remote access
  to a mobile worker and small office/home office
  (SOHO) to the headquarters of the Intranet or
  Extranet over a shared infrastructure.
• Intranet VPNs Intranet VPNs link regional and
  remote offices to the headquarters of the
  internal network over a shared infrastructure
  using dedicated connections
• Extranet VPNs Extranet VPNs link business
  partners to the headquarters of the network over
  a shared infrastructure using dedicated
  connections

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Benefits of VPNs

• A VPN is a service that offers secure, reliable
  connectivity over a shared public network
  infrastructure such as the Internet.
• They are the most cost-effective method of
  establishing a point-to-point connection between
  remote users and an enterprise customer's network

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Intranets and extranets

• Intranets are designed to permit access by users
  who have access privileges to the internal LAN of
  the organization.
• Extranets refer to applications and services that
  are Intranet based, and use extended, secure
  access to external users or enterprises.

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Importance of bandwidth

• Bandwidth is defined as the amount of information
  that can flow through a network connection in a
  given period of time.

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Pipe Analogy for Bandwidth
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Highway Analogy for Bandwidth
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Measurement

• In digital systems, the basic unit of bandwidth
  is bits per second (bps). Bandwidth is the
  measure of how much information, or bits, can
  flow from one place to another in a given amount
  of time, or seconds.

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Limitations

• Bandwidth varies depending upon the type of media
  as well as the LAN and WAN technologies used. The
  physics of the media account for some of the
  difference.
• The actual bandwidth of a network is determined
  by a combination of the physical media and the
  technologies chosen for signaling and detecting
  network signals.

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Distance and bandwidth
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File Transfer Time Calculations
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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

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Digital versus analog

• Electromagnetic waves are called analog because
  they have the same shapes as the light and sound
  waves produced by the transmitters
• 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.
• 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.
• Unlimited amounts of information can be sent over
  the smallest or lowest bandwidth digital channel.

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Networking Models

• The concept of layers is used to describe
  communication from one computer to another
• As the data passes between layers, each layer
  adds additional information that enables
  effective communication with the corresponding
  layer on the other computer
• The OSI and TCP/IP models have layers that
  explain how data is communicated from one
  computer to another.

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Network Comparisons
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Layer Communication

• Layer 4 on the source computer communicates with
  Layer 4 on the destination computer. The rules
  and conventions used for this layer are known as
  Layer 4 protocols.

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OSI model
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OSI layers

• The OSI reference model explains how packets
  travel through the
• various layers to another device on a network
• Dividing the network into seven layers provides
  the following
• advantages
• It breaks network communication into smaller,
  more manageable parts.
• It standardizes network components to allow
  multiple vendor development and support.
• It allows different types of network hardware and
  software to communicate with each other.
• It prevents changes in one layer from affecting
  other layers.
• It divides network communication into smaller
  parts to make learning it easier to understand.

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The OSI Model - Layer 1
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The OSI Model - Layer 2
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The OSI Model - Layer 3
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The OSI Model - Layer 4
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The OSI Model - Layer 5
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The OSI Model - Layer 6
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The OSI Model - Layer 7
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Peer-to-peer communications

• Each layer of the OSI model at the source
  communicate with its peer layer at the
  destination
• The protocols of each layer exchange information,
  called protocol data units (PDUs).
• Each layer depends on the service function of the
  OSI layer below it.
• The lower layer uses encapsulation to put the PDU
  from the upper layer into its data field then it
  adds whatever headers and trailers the layer
  needs to perform its function.

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Peer-to-peer communications
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TCP/IP model

• Application layer handles issues of
  representation, encoding, and dialog control.
• The transport layer deals with the quality of
  service issues of reliability, flow control, and
  error correction
• Internet layer divides TCP segments into packets
  and send them from any network
• Network layer is concerned with all of the
  components, both physical and logical, that are
  required to make a physical link

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Common TCP/IP Protocols
The relationship between IP and TCP is an
important one. IP can be thought to point the way
for the packets, while TCP provides a reliable
transport
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Comparing TCP/IP with OSI
TCP
IP
Ethernet
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Detailed encapsulation process

• If one computer (host A) wants to send data to
  another computer (host B), the data must first be
  packaged through a process called encapsulation.
• Encapsulation wraps data with the necessary
  protocol information before network transit.

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Data Encapsulation
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Data Encapsulation example
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An understanding of the following key points
should have been achieved

• Understanding bandwidth is essential when
  studying networking
• Bandwidth is finite, costs money, and the demand
  for it increases daily
• Bandwidth is measured in bits per second, bps,
  kpbs, Mbps, or Gbps
• Limitations on bandwidth include type of media
  used, LAN and WAN technologies, and network
  equipment
• Throughput refers to actual measured bandwidth,
  which is affected by factors that include number
  of users on network, networking devices, type of
  data, users computer and the server
• The formula TS/BW (transfer time size of file
  / bandwidth) can be used to calculate data
  transfer time
• Comparison of analog and digital bandwidth

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An understanding of the following key points
should have been achieved

• Network communication is described by layered
  models
• The OSI and TCP/IP are the two most important
  models of network communication
• The International Organization for
  Standardization developed the OSI model to
  address the problems of network incompatibility
• The seven layers of the OSI are application,
  presentation, session, transport, network, data
  link, and physical
• The four layers of the TCP/IP are application,
  transport, internet, and network access
• The TCP/IP application layer is equivalent to the
  OSI application, presentation, and session layers
  
• Fundamental networking devices are hubs, bridges,
  switches, and routers
• The physical topology layouts include the bus,
  ring, star, extended star, hierarchical, and mesh
  
• A WAN consists of two or more LANs spanning a
  common geographic area

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An understanding of the following key points
should have been achieved

• A SAN provides enhanced system performance, is
  scalable, and has disaster tolerance built in
• A VPN is a private network that is constructed
  within a public network infrastructure
• Three main types of VPNs are access, Intranet,
  and Extranet VPNs
• Intranets are designed to be available to users
  who have access privileges to the internal
  network of an organization
• Extranets are designed to deliver applications
  and services that are Intranet based, using
  extended, secured access to external users or
  enterprises

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