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Media and Medium Chapter 10 Transmission Media Coaxial cable - Two types (not interchangeable) 50-ohm - Uses unmodulated signal over a single channel 75-ohm - For analog signaling and high-speed digital signaling Twisted pair copper cable Shielded Unshielded Fiber-optic cable

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transmission media
Transmission Media
  • Coaxial cable - Two types (not interchangeable)
    • 50-ohm - Uses unmodulated signal over a single channel
    • 75-ohm - For analog signaling and high-speed digital signaling
  • Twisted pair copper cable
    • Shielded
    • Unshielded
  • Fiber-optic cable
  • Wireless connections
50 ohm coaxial cable
50-Ohm Coaxial Cable
  • Advantages
    • Simple to implement and widely available
    • Low cost alternative that provides relatively high rates of data transmission
  • Disadvantages
    • Can only carry data and voice
    • Limited in distance it can transmit signals
  • 10Base2 (ThinNet) – 180 Meters, 10 nodes
  • 10Base5 (ThickNet) – 500 meters, 100 nodes
75 ohm coaxial cable
75-ohm Coaxial Cable
  • Advantages
    • Allows for data, voice, and video capabilities
    • Can cover greater distances and offers more bandwidth
  • Disadvantages
    • Requires hardware to connect via modems
    • More difficult to maintain
twisted pair copper cable
Twisted Pair Copper Cable
  • Individual copper wires are twisted together to prevent cross talk between pairs and to reduce effects of EMI and RFI
  • Inexpensive alternative to coaxial cable, but cannot support the same distances
  • Long been used by telephone companies
  • Types
    • Unshielded twisted pair (UTP) – used for voice and data
    • Shielded twisted pair (STP) – used for LANs
twisted pair categories
Twisted Pair Categories
  • Category 3 (CAT 3) - For voice and data transmission
  • Category 5 (CAT 5) - Supports fast Ethernet – 8 pin configuration
  • Category 6 (CAT 6) - Supports Gigabit Ethernet, Offers backwards compatibility
fiber optic cable
Fiber-Optic Cable
  • Advantages
    • Capable of transmitting more data much further than other wiring types
    • Completely immune to effects of EMI
    • Nearly impossible to splice without detection
  • Disadvantages
    • Expensive
    • Difficult to install and manipulate
unguided transmission
Unguided Transmission
  • Uses various technologies (microwave, radio and infrared) to receive and transmit through the air
  • Vulnerable to security breaches in which unauthorized users intercept data flow
  • Difficult to secure; unguided connections cannot be physically contained easily
securing transmission media
Securing Transmission Media
  • The most vulnerable aspect of a network is the data flow as cable spans large areas and are easily compromised when a wire or cable is tapped or spliced. Common Attacks:
    • Interception of traffic usually involves the tampering of physical media as it crosses nonsecure areas
    • Interruption of traffic is caused by rendering network access devices inoperable.
securing network transmission
Securing Network Transmission
  • More difficult attacks involve unauthorized eavesdropping or sniffing of network traffic because it typically requires physical access. Common scenarios include:
    • Inserting a node that has the ability to intercept network traffic using a sniffer or some other packet analyzer
    • Modifying switch or router configurations to bypass network security devices such as firewalls
    • Resetting an interior node so that its data flows are exported to an external path
    • War driving, a common problem with wireless transmissions
securing transmission media12
Securing Transmission Media
  • Use lock and key
  • Install closed circuit security cameras
  • Use equipment that limits or eliminates signal leaks – Fiber optic
  • Use dry methods for fire extinguishing


securing transmission media13
Securing Transmission Media
  • Deploy an uninterruptible power supply
  • Implement a redundant network
  • Utilize a VPN or other encryption technology when using wireless LANs
  • Map out cabling and deploy fiber optics in unsecured areas
storage media
Storage Media
  • Provides a way to hold data at rest
  • Hard disk drive
    • Developed by IBM in 1970s
    • Ubiquitous
  • Removable storage media
    • Magnetic
    • Optical
    • Solid-state
magnetic storage media
Magnetic Storage Media
  • Coated with iron oxide
  • When data is recorded:
    • Electromagnet inside disk drive rearranges the iron oxide particles into a series of patterns that represent 0s and 1s
  • When data is retrieved:
    • Reading disk drive uses a magnetic field to read the pattern
    • Pattern is translated into data that is sent to computer in binary form
optical storage media
Optical Storage Media
  • Light and reflection transmit data
  • Most common: CD
    • Plastic disc covered by a layer of aluminum and a layer of acrylic
    • Typically can store 700 MB of data
    • Commonly used to store multimedia
compact disc
Compact Disc
  • Data is recorded by creating very small bumps in the aluminum layer on long tiny tracks
  • Data is read by a laser beam, detected by an optoelectronic sensor, and the pattern translated into bits and sent to the computer
compact disc recordable cd r
Compact Disc-Recordable (CD-R)
  • User records data onto surface of a blank disc
  • Has layer of light-sensitive dye on top of layer of reflective gold
  • High-powered laser beam burns data on the disc
    • Changes color of light-sensitive dye by pulsing in patterns
  • Write once, read many (WORM) type of media
  • Next step: compact disc-rewritable (CD-RW)
digital versatile disc dvd
Digital Versatile Disc (DVD)
  • Can store much more data than a CD
    • Tracks are thinner and closer to each other
    • Readable on both sides of the disc
  • Made out of plastic with a layer of gold, covered by a thin layer of clear polymer
  • Used to store full-length feature films
solid state storage media
Solid-State Storage Media
  • Uses a microchip upon which data is recorded directly in digital form
  • Reliable and durable; no moving parts
  • Very small
  • CompactFlash card, SmartMedia card, Memory Sticks
    • Used primarily in digital cameras, digital video cameras, digital audio recorders
secure digital multimedia cards
Secure Digital/Multimedia Cards
  • Commonly used in MP3 players and digital cameras
  • Developed to help enforce copyright protections for publishers of music and images
  • Range in size from 4 MB to 128 MB
avoiding catastrophic loss
Avoiding Catastrophic Loss
  • Make backup copies of sensitive information and store them at a separate, secure location, preferably in a fire safe
  • Use a type of media that is less likely to be corrupted or damaged (ie, solid-state)
  • Implement a thorough encryption policy to guarantee that sensitive information does not fall into the wrong hands
  • Educate the entire organization about the importance of safeguarding sensitive data
storing media
Storing Media
  • Have a policy that tracks content and location of each disk
  • Mark each medium using a standardized naming scheme
  • Store copies in a secure location
destruction of media
Destruction of Media
  • Physically destroy the media
  • Erase the data