ch. 7 Telecommunications & Network

  1. OSI & TCP/IP model
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  2. Application
    Protocols: FTP, TFTP, SNMP, SMTP, Telnet, HTTP
  3. Presentation
    • Translation into standard formats
    • Deals with Encryption and Compression
    • No protocols in this layer - just services and standards:

    • ASCII
    • EBCDIC
    • TIFF
    • JPEG
    • MPEG
    • MIDI
  4. Session

    half duplex
    full duplex
    • Set up connection Between applications
    • NFS
    • NetBIOS
    • SQL
    • RPC

    • Simplex - Communication takes place in one direction
    • Half duplex - Communication takes place in both directions but only one at a time
    • Full duplax - both directions, communicate at the same time
  5. Transport
    Handle end-to-end transmission and segmentation

    Responsible for handling computer to computer communication

    Describes the data transfer between the applications, flow control, and error detection and correction

    • TCP
    • UDP
    • SSL
    • SPX

    Two computers agree on communication and hand shake process
  6. Network
    Include internetworking service, addressing, routing

    • Describes the data transfer between networks i.e. moves data between two hosts that are not physically connected
    • Uses Internet Protocol from TCP/IP suite for addressingRouters read information on layer 3 packet and use their routing table to determine the next hop on the network

    • IP
    • ICMP
    • IGMP
    • RIP
    • OSPF
    • IPX
  7. Data Link
    Convert data into LAN or WAN frames for transmissions - converts messages to bits

    Devided into two:

    • LLC (logical Link control) - Error detection
    • MAC (Media Access Control) - Transmits and receives frames from peers that are physically connected

    • Protocols:
    • ARP - address resolution protocol
    • RARP - reverse address resolution protocol
    • PPP - Point-to-Point Protocol
    • SLIP - Serial Line Internet Protocol
  8. Physical
    • Converts bits into electrical signals - controls the physical aspects of the data transmission.
    • HSSI - High speed serrial interface
    • X.21
    • EIA/TIA-232 & EIA/TIA-449
  9. OSI Model - working parts - communication, frame,
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  10. UPD - TCP Stack
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  11. Analog Transmission
    Analog Transmission Signals - Electromagnetic waves - through a process of modulation and a pre-determined frequency for the carrier

    • Amplitude - height of signal
    • Frequency - number of waves for a period of time
  12. Digital Signals
    • Digital Signals - represent binary digits with electrical pulses
    • Bandwidth - The maximum number of pulses that can be transmitted over a link
  13. Asynchrounous Communication
    Synchrounous Communication
    • Asynchrounous Communication - communication is not synchronized. Sender can send anytime and receiver must be ready
    • Synchrounous Communication - communication between two devices that are synchronized usually through clocking mechanism
  14. Broadband
    • Broadband - splits communication channel into individual channels so that different data types can be communicated simultaneously
    • Baseband - Uses entire communication for transmission
  15. Physical Layer - Cabling
    • Copper Cable
    • Coax – bulky, heavy, but relatively immune to noise
    • Twisted pair – thinner, lighter, cheaper, and okay about noise

    • Fiber Optic Cable
    • Multi-mode – good for relatively short distances (a couple of km) and moderate speeds (< 10 Gbps)
    • Single-mode – good for short and long distances (100+ km) and virtually any speed

    Radio, Microwaves, Satellite, others
  16. Data Link Layer - Logical Topology
    • Ethernet
    • Token Ring
    • FDDI
    • ATM
    • SLIP/PPP
    • Frame Relay
    • SONET
    • Waxed String
  17. Ethernet
    IEEE Standard
    • Ethernet
    • Ethernet has a very simple transmission control protocol


    • Listen to the network
    • If someone is talking, wait your turn
    • If no one is talking, send your data
    • If someone starts talking while you are talking, stop talking and scream at them!

    Ethernet uses CSMA/CD - Carrier Sense Multiple Access with Collision Detection
  18. TCP
    • Transmission Control Protocol
    • Connection-oriented
    • Stream based
    • Reliable - In order, Once and only once
    • “Heavy weight” - 3-way handshake

    • Common uses:Remote login (Telnet, RSH/Rlogin, SSH)
    • File Transfer (FTP, SCP, HTTP)Newer NFS
  19. UDP
    • UDP – The User Datagram Protocol
    • Connectionless
    • Datagram based
    • Unreliable“Quick & Dirty”

    Common uses:Domain Name System (DNS)Simple Network Management Protocol (SNMP)Older Network File System (NFS)
  20. unicast transmission

    broadcast transmission

    multicast transmission
    Unicast transmission - Occurs when a packet is sent from one source computer to one destination computer

    Broadcast transmission - occurs when a packet is sent from one source computer to all computers on a certain network segment

    Multicast Cattransmission - Occurs when a packet is sent from one source computer to several specific computers
  21. Bus Topology
    Uses linear, single cable for all computers. All traffic travels the full cable. All data can be viewed by users.

    Problems - if one segment goes down it can negitavely affect computers on the same line

  22. Ring
    All computers are connected in a unidirectional communication link.

    The cable is a closed loop

    PRoblem - one station goes down it can affect other computers on same ring

  23. Star
    All computers are connected to a central hub

    PROBLEM - the central device is a single point of failure

    Logical bus (Ethernet) and ring topolgies (Token Ring)
  24. Tree
    A bus topology that does not have one linear cable but instead uses branches of cables

    PROBLEM - none

  25. MESH
    Computers are connected to each other - more redundancy

    PROBLEM - Expensive

  26. Types of Ethernet
    10Base2 - ThinNet - Coax Cable - maximum cable length of 185 meters, requires BNC connectors

    Speed 10bps
  27. Types of Ethernet
    • Thicker cable than 10Base2
    • Coax cables
    • BNC connectors
    • Usually used as network backbone
    • * more resistent to electric interference
  28. Types of Ethernet
    • twisted pair copper wiring
    • RJ-45 Connector
    • usually implemented in a star topology
    • 10 Mbps
  29. Types of Ethernet
    Fast Ethernet
    • uses CSMA/CD
    • 100 Mbps
  30. Token Ring
    Active Monitor
    • IEEE Standard 802.5
    • Uses token passing technology
    • Uses star-configured topology - ring - how the signal travels

    Each computer is connected to cenral hub - MAU - Multi-Station-Unit

    Token-passing technology - Cannot communicate unless a machine has a token ( a control frame) that travels in a logical circle.

    Active Monitor- Removes tokens that are endlessly circling the network
  31. FDDI
    • high-speed token passing media access technology
    • 100 mbps - typically backbone network using fiber optic cable

    Fault tolerance - counter rotating fiber ring - if one goes down, the othe ring will be activated
  32. Coaxial cable
    • 10Base2
    • 10Base5

    • Higher bandwidth
    • resistent to electromagnetic interference (EMI)

    baseband (one channel) and broadband (multi-channel) methods
  33. Twisted Pair
    Cross Talk
    • Shielded Twisted Pair - add resistents to radio frequency and EMI
    • Unshielded Twisted Pair - Less resistence to radio frequency and EMI

    The more twisted the wire, the more resistent the cable is interference and attenuation

    Cross-Talk - UTP can electrical signals spill from one wire to another
  34. UTP cable ratings
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  35. Fiber Optic
    • Glass that carries light waves
    • More resistent to attenuation and EMI than copper wires
    • Does not radiate signals
    • higher speeds and longer distances

    Used as backbone to networks
  36. LAN protocols
    ICMP - Loki Attack
    • ARP - knows IP and broadcasts to find MAC - ARP table poisoning masquerading
    • RARP - knows MAC broadcasts to find IP
    • DHCP
    • ICMP - Loki Attack - send data within ICMP packet to compromised system - backdoor
  37. Routing Protocols -
    Distance Vector
    • Dynamic - Router updates routing table and makes decision of routing path
    • Static - Admin has to update
    • Distance Vector - dicsion based on number of hops and vector (direction)
    • Link-state - database of network topology - look at packet size, speed, delay, ... etc.
  38. Interior Routing Protocols
    • Routing Information Protocol - How routers share information
    • - not in use - no authentication, slow performance
  39. Interior Routing Protocols
    • Open Shortest Path
    • link-state algorithms to send out routing table information - smaller more frequent routing table updates
    • requires more memory and CPU

    Authentication in clear text or hashed
  40. Interior Routing Protocols
    Interior Gateway Routing Protocol - distance vector routing protocol - Cisco systems - 5 criteria to determine best route.
  41. Exterior Routing Protocol
    Border Gateway Protocol - How border routers share information with other networks. Uses link-state and distance-vector routing algorithms.
  42. Worm hole attack
    An attacker can capture a packet at one end of a network and tunnel it to another location on the network

    two attackers

    countermeasure - leash - data on on header of packet - restricts packet distance
  43. Repeaters
    • Repeaters - physical
    • Bridge - data link
    • Switch - data link - network
    • Router - network

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  44. Difference between Bridges and Routers

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  45. MLPS
    Multi-Level Protocol Switching - Used to address service requiremest for different kinds of packets - VOIP or video conferencing
  46. Stateful inspection firewalls
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  47. Pros and Cons of Proxy firewalls
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  48. Applicaton Level - vs. circuit levle proxy firewall characteristics
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  49. Firewall Types
    Packet filtering
    application-level Proxy
    circuit-level Proxy
    Kernel Proxy
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  50. Firewall Architecture
    Dual Homed
    Screened Host
    Screened Subnet
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  51. MAN
    • Metropolitan Area Network
    • SONET or FDDI - provided by telecommunication providers .

    SONET - Synchronous Optical Networks - dual rings - redundancy
  52. WAN Technologies:
    Channel Service Unit/Data Service Unit - required to connect a LAN to a WAN
  53. WAN Technologies
    Switching - Circuit vs. Packet
    Circuit Switching - Acts like a dedicated link

    Packet Switching - traffice can pass through a various number of hops

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  54. WAN Protocol: Frame Relay
    • Works on Data-Link layer
    • Cost based on amount of bandwidth - Commited information rate (CIR)
    • DTE - Data Terminal Equipment - Company owned router
    • DCE - Data Circuit-Terminating Equipmentd - Service Provider network equipment - performes the traffic movement
    • Costs less than leased line
  55. Multiplexing
    Combining multiple channels of data over a single transmission path.

    • Statistical time-division multiplexing (STDM)
    • Uses statistics for the workload of each inputdevice and determines the real time how much each device should be allocated for data transmission

    • Frequency-division multiplexing
    • - each frequency in a wireless spectrum is used to move data
  56. CSU/DSU
    Channel Service Unit/Data Service Unit - Requried when digital equpment will be used to connect a LAN to a WAN.
  57. Virtual Circuits - used in frame relay and X.25
    • PVC - Permanent Virtual Circuit - works like a privite line - agreed upon badwidth adn availalbility. Path established
    • SVC - Switched virtual Circuit - Circuit must be built - required bandwidth
  58. WAN Protocol
    • Older WAN protocol - how devicesa dn entworks establish and maintain conenctions.
    • data devided into 128 bytes and enca;uslated in High-level Data Link Control (HDLC) frames
    • Not very efficient
  59. WAN Technology
    • Asynchronous Transfer Mode (ATM) -
    • Uses cell-switching instead of packet switching. Data segmented int fixed size cells of 53 bytes. (instead of variable size packets).
    • Uses virtual circuits
    • Good for voice and video
  60. QoS
    Quality of Service - protocol can distinguish between different classes of messages - priority level

    CBR - Constant Bit Rate - Connection oriented channel - provides a consistent data through put of rtiem-sensitive applciations. customers specify bandwidth

    VBR - Connection oriented channel - customers specify requried peak and sustatied rate of data throughput - variable bandwidth and speed

    UBR - A connectionless channel that does not promise data through put

    ABR- Connection oriented channel - allows the bit rate to be adjusted. Customers are given the bandwidth remaining
  61. QoS levels
    • Best Effort
    • Differentiated service - less drops, more bandwidth, shorter delays
    • guaranteed servcie - time sensitive data - voice and video
  62. SMDS
    • Switched Multimegabit Data Service - High speed packet-switched thecnology used to enable customers to extend their LANs acros MANs and WANs.
    • Connectionless -- REPLACED by FRAME RELAY
  63. SDLC
    Synchronouse Data Link Control protocol - networks that use didicated, leased, or permanent physical connections. Used mainly for IBM hosts and mainframes to communicate to remote locations.
  64. HDLC
    HDLC (High-Level Data Link Control) - protocol - extension of SDLC - high throughput, full-duplex .. point to point or multipoint networks
  65. HSSI -
    • High-Speed Serial Interface - interface used to connect multiplexers and routers to high-speed communication servcies - such as ATM and frame relay
    • Physical Layer
  66. Multiservice Access Technologies
    Multiservice Access Technologies - combine several types of communication categories over one transmission line
  67. Wan Technology Summary
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  68. ISDN

    Integrated Services Digital Network - Communication protocol provided by telephone companies and IPSs - uses equipment to transport digital data over phone lines.

    • BRI - two channels that enable data to be transfeered adn one D channel tha provides for call setup ... ID .. etc
    • PRI - 23 B channels and 1 D channel - used in corporations as a backup communication solution

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  69. DSL

    Digital Subscriber Line - 6 to 30 times faster than ISDN - 52 MBPS

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  70. Tunneling Protocols

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  71. Authentication Protocols
    CHAP vs. PAP
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  72. Spread Spectrum Types
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  73. Wireless standards
    • 802.11b - most common
    • 802.11a - in 'dirty range of frequency' - must be close to AP, may not work in other countries
    • 802.11e - implemented QoS
    • 802.11f - Allows users to roam - APs can talk to each other and make sure a user is authenticated
    • 802.11g - higher transfer rates - up to 54 MBPS
    • 802.11h - builds upon 802.11a - adapts type of data transmission for European wireless rules
  74. 802.11i
    • 802.11i - use of EAP (Extensible Authentication Protocol) and 802.11x to enforce user authentication and mutual authentication.
    • TKIP - Temperal Key Integrity Protocol
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ch. 7 Telecommunications & Network
Telecommunications & Network, Cissp