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Media and Medium

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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Media and Medium

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  1. Media and Medium Chapter 10

  2. 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

  3. 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

  4. 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

  5. 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

  6. 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

  7. 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

  8. Comparison ofWired Transmission Media

  9. 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

  10. 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.

  11. 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

  12. 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 continued…

  13. 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

  14. 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

  15. 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

  16. 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

  17. 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

  18. 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)

  19. 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

  20. 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

  21. 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

  22. 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)

  23. Encryption • 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

  24. 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

  25. Destruction of Media • Physically destroy the media • Erase the data

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