Concepts for the Final Exam

Chapter 5

Chapter 5: The Link Layer and Local Area Networks

• Layer functionality
  • primary functionality: move data across a single link
  • possible problems
    • noise
    • contention for link
    • node data handling limits
  • possible services
    • framing
    • error handling
    • controlling link access
    • flow control
• Link types
  • point-to-point
  • broadcast
  • distinction between logical and physical type
• Error detection/correction
  • general strategy
  • error detection code schemes
    • parity bit
    • two dimensional parity
    • cyclic redundancy codes
• Multiple access protocols
  • channel partitioning (TDM, FDM)
  • random access
    • use of carrier sense and collision detection
    • Aloha
    • taking turns
    • Ethernet
• Link layer addressing
  • MAC addresses
  • Address resolution protocol
• Ethernet and local area networks
  • physical and logical topology of an ethernet segment
  • LAN organization
    • hubs (physical layer)
    • switches (link layer)
    • routers (network layer)
    • drawbacks of hubs
• Point-to-point protocol (telephone modems)
• Link virtualization
  • ATM and telecommunications
  • ATM links in the internet

Chapter 8: Security in Computer Networks

• Authorization
  • passwords
  • encrypted passwords
  • nonces
• Encryption
  • symmetric key
    • same key used for both encryption and decryption
    • fast algorithms, good for secret connections
    • one-time keys can be obtained from a key distribution center
    DES, AES, for example
  • public key
    • different keys used for encryption and decryption
    • public key is known to all, private key is only known to the owner
    • slower algorithms
    • for secret communication, sender encrypts with the receivers public key
    for digital signatures, signer uses their ow private key
    • typically, message digests are signed rather than the entire message
    • RSA, for example
• Message digest algorithms
  • MD5
  • SHA-1
• Firewalls
  • packet filtering
  • application gateways
• Attacks and countermeasures
  • mapping
  • packet sniffing, switches
  • spoofing, engress filtering
  • denial of service
  • distributed denial of service
  • hijacking

Chapter 9: Network Management (9.1, 9.2)

• What is it?
  • monitoring
  • analysis
  • control
    • reactive
    • proactive
• ISO areas of network management
  • performance management
  • fault management
  • configuration management
  • accounting management
  • security management