Networking Basics CCNA 1 Chapter 2

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Networking Basics CCNA 1Chapter 2
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Networking Basics and Terminology

• A Brief History of the Networking Universe
• Earliest commercial computers were large
  mainframes, run by computer scientists
• Terminals were invented, allowing users to
  interact with the computers
• Eventually (1960s), some terminals were located
  to allow remote access

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Networking Basics and Terminology

• A Brief History of the Networking Universe
• By late 1960s minicomputers entered marketplace
• Minis were smaller, less powerful and less
  expensive than mainframes
• Mid 1970s First personal computers (PCs) built
  by researchers

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Networking Basics and Terminology

• A Brief History of the Networking Universe
• 1977 Apple introduces the Apple-II
• 1981 IBM introduces its first PC
• Mid 1980s Computer users with standalone
  computers start sharing data through the use of
  modems connecting to another computer (dialup,
  point-to-point)

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Networking Basics and Terminology

• The Need for Networking Protocols and Standards
• 1960s to 1980s Each vendor set its own
  proprietary protocols and standards
• Equipment from different vendors would not
  interoperate
• Eventually, open standards were agreed upon
• Open standards allow more competition, which
  increases speed of development

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Networking Basics and Terminology

• Popular Network Standards Organizations

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Networking Basics and Terminology

• Ethernet LANs and LAN Devices
• Ethernet LANs originally used coaxial cable
  (similar to Cable TV cable)
• Network Interface Cards (NICs) would attach to a
  length of cable called a segment

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Networking Basics and Terminology

• Ethernet LANs and LAN Devices
• In early Ethernet LANs, all devices sent their
  data on one wire
• All other devices on the segment received the
  signal
• These types of Ethernet are said to be
  broadcast media, because any signal sent by one
  device is received by all other devices

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Networking Basics and Terminology

• Characteristics of Early Ethernet LANs
• Limited to a relatively small geographic area
• Allows multiple devices access to high-speed
  media
• Administrative control rests within a single
  company
• Provides full-time connectivity
• Typically connects devices that are close together

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Networking Basics and Terminology

• Cisco Networking Device Icons

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Networking Basics and Terminology

• Ethernet Repeaters
• When a signal is sent over a wire, it degrades
• 10BASE5 limited a single segment to 500 meters
  10BASE2 to a little less than 200 meters (185
  meters) hence their names (the 5 and the 2 the
  10 is for 10Mbps)
• To extend the distance of LANs, repeaters were
  developed

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Networking Basics and Terminology

• Features of Ethernet Repeaters
• Typically had two ports connecting two different
  Ethernet segments
• Interpreted the incoming signal on one port as
  1s and 0s
• Sent a regenerated clean signal out the other port

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Networking Basics and Terminology

• Repeated Ethernet Signal
• See Conceptual View on next slide
• Betty sends a clean signal
• The signal degrades by the time it reaches the
  repeater
• The repeater regenerates a new, clean signal and
  sends it out its other port

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Networking Basics and Terminology

• Repeated Ethernet Signal

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Networking Basics and Terminology

• Ethernet Hubs and 10BASE-T
• Coax cables were expensive and difficult to work
  with
• If the cable broke, everyone on the LAN had
  problems
• Lead to the creation of 10BASE-T

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Networking Basics and Terminology

• Ethernet Hubs and 10BASE-T
• The 10 means it runs at 10Mbps
• The T means that it uses twisted-pair cable
• The cable is Unshielded Twisted-Pair (UTP), which
  is cheaper than coax cable
• Smaller diameter than coax cable
• Terminated with RJ-45 connectors

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Networking Basics and Terminology

• 10BASE-T with a Hub Star Topology

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Networking Basics and Terminology

• Functions of a Hub
• Provides RJ-45 jacks so cables with RJ-45
  connectors can be attached
• Repeats any incoming signal out all other ports
• Was originally called a multiport repeater

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Networking Basics and Terminology

• Ethernet Bridges
• Examine incoming signal, interpret signal as 0s
  and 1s, find the destination MAC address listed
  in the frame
• If destination MAC address is reachable via a
  different interface than the one on which it was
  received, then clean, regenerate and forward the
  frame out that interface
• If the destination is reachable on the same
  interface on which it was received, discard the
  frame (this is called filtering)

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Networking Basics and Terminology

• A Bridge Making a Filtering Decision

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Networking Basics and Terminology

• A Bridge Making a Forwarding Decision

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Networking Basics and Terminology

• Ethernet Frames
• An Ethernet frame is the data sent by an Ethernet
  NIC or interface
• The first bits sent are the header contains info
  such as the destination and source MAC addresses
• Includes headers from other protocols, such as IP

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Networking Basics and Terminology

• Conceptual View of an Ethernet Frame

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Networking Basics and Terminology

• Unicast and Broadcast Ethernet Frames and
  Addresses
• Before the introduction of bridges, the LAN acted
  as a broadcast medium
• The term unicast MAC address identifies a single
  NIC or Ethernet interface
• Sometimes a computer needs to send a frame that
  will reach all devices on the LAN it uses a
  broadcast address FFFF.FFFF.FFFF
• All devices must process data sent to this address

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Networking Basics and Terminology

• LAN Switches
• Like a hub, a switch provides a large number of
  ports/jacks to plug in cables
• Forms a physical star topology
• When forwarding a frame, the switch regenerates a
  clean signal
• Like bridges, switches use the same
  filtering/forwarding logic on a per-port basis

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Networking Basics and Terminology

• A Switch Making a Forwarding Decision

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Networking Basics and Terminology

• Wide-Area Networks (WANs)
• Cover a large geographic area
• WAN Technologies
• Modems
• Integrated Services Digital Network (ISDN)
• Digital Subscribe Line (DSL)
• Frame Relay
• T1 or E1 leased lines T1, E1, T3, E3, etc.
• Synchronous Optical Network (SONET) synchronous
  transport Level 1(STS-1) optical carrier OC-1,
  STS-3 (OC-3), etc.

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Networking Basics and Terminology

• Point-to-Point Leased Lines
• A point-to-point leased line extends between two
  locations
• The line is not owned by the user it is leased
  from a service provider
• The service provider is often a telephone company
  (telco)
• Often, the term link is used to describe a
  point-to-point leased line

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Networking Basics and Terminology

• Point-to-Point Leased Lines
• Leased lines are drawn like lightning bolts

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Networking Basics and Terminology

• Routers and Their Use with LANs
• Routers perform a basic but very important
  forwarding process in which they receive data
  packets and then forward the packets toward the
  destination
• Routers can send and receive traffic on most any
  kind of physical networking media
• Routers are the perfect device to connect a LAN
  to a WAN

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Networking Basics and Terminology

• Metropolitan Area Networks (MANs)
• A medium-sized network geography, perhaps
  city-wide
• Usually very high speed
• Optical media used between routers can move data
  at 10 Gbps or even 40 Gbps

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Networking Basics and Terminology

• High-Speed City-Wide MAN

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Networking Basics and Terminology

• Storage-Area Networks (SANs)
• Allow computers to communicate with storage
  devices
• Features of SANs
• Performance concurrent access of disk or tape
  arrays
• Availability used to back up data to offsite
  locations
• Scalability easy relocation of backup data,
  operations, file migration, and data replication
  between systems

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Networking Basics and Terminology

• Typical SAN Used by a Server Farm

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Networking Basics and Terminology

• Virtual Private Networks (VPNs)
• Companies can use the Internet to send data
  between sites, instead of using leased lines
• Often less expensive than leased lines
• Can be less secure than leased lines

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Networking Basics and Terminology

• Virtual Private Networks (VPNs)

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Networking Basics and Terminology

• Intranet VPNs
• Packets are encrypted before they leave for the
  Internet
• Not practical for a hacker to break the
  encryption
• Intranet VPNs are used inside a single
  organization

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Networking Basics and Terminology

• Intranet VPN

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Networking Basics and Terminology

• Comparing Intranet VPNs to Extranet
• and Access VPNs
• Intranet VPN A VPN between sites of a single
  organization
• Extranet VPN A VPN between sites of different
  organizations
• Access VPN A VPN between individual users and
  an enterprise network, allowing access while
  working from home or traveling

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Networking Basics and Terminology

• Extranet and Access VPNs

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Networking Basics and Terminology

• Physical Network Topologies

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Networking Basics and Terminology

• Physical Bus Topology
• 10BASE2 and 10BASE5 use a bus topology
• Looks like a city street where each of the
  computers is a bus stop
• A frame sent by one device is received by all
  other devices

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Networking Basics and Terminology

• Physical Star Topology
• 10BASE-T Ethernet connects with a hub
• The hub is the device at the center, so it
  resembles a start
• The actual physical layout of the cable may not
  be in a star pattern

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Networking Basics and Terminology

• Logical Bus Topology
• Logical refers to how the network operates, not
  where the cables run
• 10BASE-T is a logical bus, because all devices
  see any signal sent by other devices on the
  network

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Networking Basics and Terminology

• Physical versus Logical Topology
• Physical Topology The topology is determined by
  the physical layout of the cabling and
  transmission media
• Logical Topology The topology is determined by
  the media access control logic and how the
  devices collectively send traffic over the network

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Networking Basics and Terminology

• Typical Modern LAN and Its Similarities to a
  Star Topology

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Networking Basics and Terminology

• Typical Modern LAN Design for a Single Building

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Networking Basics and Terminology

• Ring Topologies
• Cable is installed from first device to second
  device, second device to third device, and so on,
  until the last device connects to the first
  device
• Each device cleans up the signal, so fewer
  repeaters are needed
• Can have single or dual rings

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Networking Basics and Terminology

• Ring Topology
• R1 and R2 detect that cable between them is cut
• R1 and R2 loop the primary ring to the backup
  ring using circuitry in the routers
• One ring still works, assuring connectivity

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Networking Basics and Terminology

• Hierarchical and Extended Star Topologies
• A central device or site connects to several
  other sites
• Much like a star topology
• The other sites then connect to still more sites
• Extended star topologies have the same features
  as a hierarchical topology, but are not drawn in
  a hierarchy

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Networking Basics and Terminology

• Hierarchical Network Design

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Networking Basics and Terminology

• Mesh Full and Partial
• Most often refers to WAN topologies
• Full mesh all devices connect to all other
  devices highly reliable Frame Relay is an
  example
• Partial mesh Each device connects to many, but
  not all, other devices

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Networking Basics and Terminology

• Mesh Full and Partial

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Bandwidth

• Bandwidth Number of bits per second that can
  be sent by a device across a particular
  transmission medium
• Names and Units of Digital bandwidth

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Bandwidth

• LAN and WAN Bandwidth
• Actual speed is limited by 3 factors cabling,
  cable length, and the speed at which the devices
  on the end of the cable try to send data
• Ethernet standards call for Category 5 (Cat 5)
  UTP cabling, for speeds of 10, 100 and even 1000
  Mbps
• The cable can handle higher speeds, but is
  hardware limited

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Bandwidth

• Bandwidths for Various Ethernet Standards and
  Cables

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Bandwidth

• WAN Bandwidths
• Vary significantly, as do LAN bandwidths
• Engineers need to worry about details such as
  cable length restrictions and required equipment
• Customers need to worry about how fast the WAN
  link is, how much it costs, and the type of
  technology used

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Bandwidth

• WAN Bandwidth Standards

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Bandwidth

• WAN Bandwidth Standards (continued)

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Bandwidth

• Throughput Versus Bandwidth
• Throughput is how many bits are actually
  transferred between two computers in a given time
• Two points to consider when comparing throughput
  to bandwidth
• Throughput rate may vary over time due to network
  conditions bandwidth does not vary over time
• Bandwidth defines the speed of a single link
  throughput measures the speed of the end-to-end
  connection

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Bandwidth

• Two Examples of Throughput

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Bandwidth is What You Pay for, Throughput is What
You Get

• Factors That Affect Throughput
• Networking devices in the route being used
• Type of data being transferred
• Protocols used to transfer the data
• Topology of the network
• Congestion level in the network
• Speed and current workload of the computers
• Time of day ( of active concurrent users)

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Bandwidth

• Calculating Data Transfer Time Two Methods

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Bandwidth

• Calculating Data Transfer Time
• Four Examples from the Two Examples of
  Throughput Slide

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Bandwidth

• Analog Bandwidth
• In the analog world, a number of consecutive
  frequencies (a band of frequencies) defined how
  much information could be sent with an analog
  signal
• The wider the band of frequencies, the more
  information could be sent
• With digital transmission, the range of
  frequencies does not affect the speed, but the
  term bandwidth is still used to describe the
  speed of the bits across a link

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Bandwidth

• Analog Bandwidth (continued)
• Analog transmission requires a set frequency band
  to work
• The figure below shows a 3-hertz signal

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Bandwidth

• Planning for Bandwidth
• Neither LAN nor WAN bandwidth is free
• On enterprise networks, WAN costs can be 30-40
  of the total budget
• LAN links cost money, due to wiring costs and the
  costs of networking devices such as switches
• Bandwidth is not infinite, and it costs money to
  upgrade

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Bandwidth

• Planning for Bandwidth (continued)
• Four reasons why bandwidth is important
• Bandwidth is finite
• Bandwidth is not free
• Network engineers need to plan for bandwidth
• Bandwidth demand is ever-increasing

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The OSI and TCP/IP Networking Models

• Networking models define a related set of
  standards and protocols
• When used together, these protocols and standards
  allow the creation of a working network
• The two most commonly used models are the Open
  Systems Interconnection (OSI) model and the
  Transmission Control Protocol/Internet Protocol
  (TCP/IP) model

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The OSI and TCP/IP Networking Models

• In the 1960s, vendors each used their own set of
  standards and protocols
• These proprietary networking models would not
  allow equipment from one company to work with
  equipment from another company
• To overcome this problem, the OSI model was
  developed beginning in 1984

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The OSI and TCP/IP Networking Models

• The OSI Model
• Goal was to be the one open networking model that
  all vendors would implement
• The term open means that all vendors have
  access to the protocols and rules for building
  products
• Most vendors worked toward adopting the OSI model
  in the late 1980s and early 1990s
• Many vendors and networking professionals adopted
  the OSI terminology to hold meaningful
  conversations about different networking models,
  making those conversations a little easier

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The OSI and TCP/IP Networking Models

• The OSI Model (continued)
• The OSI model might have been the final standard
  for networking, but TCP/IP proved to be more
  widely accepted
• Computers today rarely implement the OSI model as
  their model for networking
• Why use OSI? The terminology is still used, and
  it is useful in troubleshooting networking
  problems

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The OSI and TCP/IP Networking Models

• The OSI Layers
• General networking functions are defined in
  layers
• Allows better standardization of different
  components
• Opens up competition in marketplace
• Standardizes components
• Standardizes interfaces between different layers,
  allowing companies to focus on one layer
• Prevents changes in one layer from affecting
  other layers
• Breaks network communication into smaller
  components

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The OSI and TCP/IP Networking Models

• The OSI Layers

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The OSI and TCP/IP Networking Models

• Memorizing the Order of the OSI Layers
• Starting with Layer 1
• Please Do Not Take Sausage Pizza Away
• Pew! Dead Ninja Turtles Smell Pretty Awful

• Starting with Layer 7
• All People Seem To Need Data Processing

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The OSI and TCP/IP Networking Models

• Functions of the OSI Layers
• Layer 7 (application layer)
• Provides services to end users applications
• Does not provide services to any other OSI layer
• Layer 6 (presentation layer)
• Ensures info from one systems application layer
  can be read by another system
• Translates among multiple data formats
• Does encryption and decryption
• Handles graphics standards such as PICT, TIFF,
  JPEG, MIDI and MPEG

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The OSI and TCP/IP Networking Models

• Functions of the OSI Layers (continued)
• Layer 5 (session layer)
• Establishes, manages and terminates sessions
  between two hosts
• Layer 4 (transport layer)
• Segments data given to it by the session layer
  into smaller chunks
• Defines error-recovery services

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The OSI and TCP/IP Networking Models

• Functions of the OSI Layers (continued)
• Layer 3 (network layer)
• Provides connectivity and path selection between
  two host systems
• Concerned with logical addressing
• Layer 2 (data link layer)
• Provides transit of data across a physical link
  by defining the rules about how the link is used
• Concerned with physical addressing
• Layer 1 (physical layer)
• Defines electrical, mechanical, procedural, and
  functional specifications for activating,
  maintaining, and deactivating the physical link
  between end systems

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The OSI and TCP/IP Networking Models

• Relationship of OSI Layers and Devices

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The OSI and TCP/IP Networking Models

• The TCP/IP Networking Model
• Began as part of a research project for the US
  Dept. of Defense (DoD) in the 1970s.
• The structure remains the same today, but many
  new protocols have been added
• Can be easily compared to the OSI model uses 4
  layers instead of 7

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The OSI and TCP/IP Networking Models

• The TCP/IP Reference Model Layers

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The OSI and TCP/IP Networking Models

• Encapsulation
• Application headers are added
• Data is segmented
• IP address information is added
• Data link header and trailer are added
• Bits are transmitted

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The OSI and TCP/IP Networking Models

• Segments, Packets, Frames, and PDUs
• Important to know the terminology for the group
  of bytes at each layer
• The generic term is protocol data unit (PDU)

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The OSI and TCP/IP Networking Models

• De-encapsulation
• Physical layer interprets incoming electrical
  signal
• Contents of Ethernet header and trailer analyzed
  IP packet extracted
• Network layer verifies IP header is okay,
  extracts contents of data field
• Segments are reassembled and error recovery
  performed
• Data is given to application

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The OSI and TCP/IP Networking Models

• Layer Interactions
• Same layer interaction creation of headers, and
  possibly trailers, by a protocol at one
  networking layer on one computer, with the goal
  of communicating to the same layer and protocol
  on another computer
• Adjacent layer interaction On a single
  computer, the interaction of protocols that sit
  at adjacent layers of their networking model.
  Includes exchange of data during encapsulation
  and de-encapsulation, and how a lower layer
  protocol provides service to an upper layer
  protocol

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Networking Fundamentals

• Summary
• Network devices (hubs, repeaters, bridges,
  switches, routers) connect host devices to allow
  them to communicate
• Protocols provide sets of rules for communication
• The physical topology is the actual layout of the
  wire or media
• Common physical topologies are bus, ring,
  star,extended star, hierarchical, and mesh
• A LAN is designed to work in a limited
  geographical area, providing multi-access to
  high-bandwidth media
• LANs are controlled privately under local
  administration
• LANs provide full-time connectivity to services
  and connect physically adjacent devices

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Networking Fundamentals

• Summary
• WANs operate over large geographical areas
• WANs allow access serial interfaces that operate
  at lower speeds, provide full- and part-time
  connectivity to local services and connect
  devices separated over large areas
• A MAN is a network that spans a metropolitan area
  such as a city
• A SAN is a dedicated, high performance network
  used to move data between servers and storage
  resources
• SANs are scalable and have disaster tolerance
  built it
• A VPN is a private network constructed with a
  public network infrastructure such as the
  Internet
• The three main types of VPNs are access, intranet
  and extranet

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Networking Fundamentals

• Summary
• Access VPNs provide mobile workers connectivity
• Intranet VPNs are only available to users who
  have access privileges to the internal network of
  an organization
• Extranet VPNs are design to provide applications
  and services to external users or enterprises
• Bandwidth equals number of bits per second (bps)
  that can theoretically be sent through a network
  connection
• Throughput is the amount of data that actually
  passes through a connection in a give time, and
  is constrained by the slowest link between the
  two end devices
• Analog bandwidth is a measure of how much of the
  electromagnetic spectrum is occupied by each
  signal
• Digital bandwidth is measured in bits per second

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Networking Fundamentals

• Summary
• Layers are used to describe communication from
  one computer to another because it
• Reduces complexity
• Standardizes interfaces
• Facilitates modular engineering
• Ensures interoperability
• Accelerates evolution
• Simplifies teaching and learning
• Two models are the OSI model and the TCP/IP model
• The OSI model has seven layers the TCP/IP model
  has four some layers have the same name but do
  not correspond exactly

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Networking Fundamentals

• Summary
• Data is encapsulated with these steps
• Images and text are converted to data
• Data is packaged into segments
• Each data segment is encapsulated in a packet
  with source and destination addresses
• Each packet is encapsulated in a frame with the
  MAC address of the next directly connected device
• Each frame is converted to a pattern of 1s and 0s
  and transmitted on the media