Ch. 9 Key Terms

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Ch. 9 Key Terms
2011-12-12 17:55:39
Chapter Nine Ethernet Network Fundamentals CCNA Exploration Companion Guide

Chapter Nine Ethernet, Network Fundamentals, CCNA Exploration Companion Guide
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  1. asynchronous
    Communication that does not use a common clock between the sender and receiver.

    Additional info is sent to maintain timing, synch and receive circuit to the incoming data.

    10Mbps Ethernet device does not send sync signals.
  2. ARP table / cache
    Logical storage in host's RAM to store ARP entries.
  3. ARP spoofing / poisoning
    Technique to attack an Ethernet network by sending fake ARP messages to an Ethernet LAN.

    Frames contain false MAC addresses that "confuse" network devices (ex: switches).

    Causes frames intended for one node could be sent to another by mistake.
  4. bridge
    Device that connects multiple network segments at the data link layer of the OSI model.

    Predecessor to the LAN switch.
  5. bridge table
    Used by a switch or bridge that associates MAC addresses with the outgoing port.

    Uses table as reference for forwarding & filtering.
  6. bridging
    Process of forwarding frames in a switch or bridge from one port to another port from segment to segment.
  7. BIA
    Burned-In Address

    MAC address that is permanently assigned to a LAN interface or NIC.

    • Burned onto the chip on the card.
    • Can not be changed.

    aka UAA (Universally Administered Address)
  8. CSMA/CD
    Carrier Sense Multiple Access / Collision Detect

    MAC algorithm used by Ethernet devices in a shared media.

    Protocol requires a node listen for existing signal on the media before attempting to send its data.

    If signal is found the node waits until the media is clear before transmit.

    If collision occurs and/or is detected the sending node issues a back-off algorithm before retransmitting.
  9. collision domain
    Physical or logical area in a LAN where the signal sent by the interfaces may be subject collision.

    Every device in the same collision domain receives frames sent out by other devices on that same segment.

    • Hubs increase the size of the collision domain.
    • Switches separate them.
  10. delimiter
    Field of a frame signals the beginning or end of a frame.
  11. extended star
    Network topology characterized by a central location connected to multiple hubs.

    Hierarchical topology but typically drawn w/ central site in the center.

    aka hierarchical star
  12. Ethernet PHY
    Physical interface transceivers.

    Deals with Layer 1 of Ethernet.
  13. flooding
    Switch/bridge process to forward broadcasts & unknown destination unicasts out all ports except the one frame is received on.
  14. filtering
    Ethernet switch/bridge process that decides not to forward a frame out another port.
  15. forwarding
    Ethernet switch/bridge process that decides to forward a frame out another port.
  16. FastEthernet
    Common name for Ethernet technology that operates at 100 Mbps.
  17. Gigabit Ethernet
    Ethernet that transmits data at 1,000,000,000 (1billion) bits per second.
  18. host group
    Group defined by a class D address

    (multicast, ranging -

    Hosts can pertain to multicast groups.

    Groups = hosts with same multicast address
  19. hub
    Ethernet device that receives an electrical signal in one port -interprets the bits- regenerates the signal out all ports.

    • Several ports
    • Extends networks - collision domains
    • Repeaters
    • Usually RJ-45
  20. interframe spacing
    Time period between Ethernet frames that inserts a space between frames.

    {allows fairness with the CSMA/CD algorithm }
  21. jam signal
    A shared media Ethernet network signal generated when a collision is detected.

    Lasts long enough for all devices to receive.

    Part of CSMA/CD.
  22. LAA
    Locally Administered Address

    MAC address that can be configured on a device.

    Can be used in place of BIA.

    Allows NIC to be replaced or device substituted w/o changing the address used by the network to access the station.
  23. latency
    Time that passes while some event occurs.

    Refers to the time that occurs between when something is sent in a network until it is received by another device.
  24. MAC table
    Table on a switch that lists all known MAC addresses and the association port for forwarding frames.
  25. MAN
    Metropolitan-Area Network

    Networks geographic size - between LAN and WAN [in size].

    Used by ISPs to create high-speed networks in metropolitan areas.
  26. OUI
    Organizational Unique Identifier

    First half of MAC address.

    Manufacturers must register the value of the OUI with the IEEE.

    Identifies manufacturer of Ethernet NIC or interfaces.
  27. Pad
    Part of the Ethernet frame that fills in the data field to ensure that the data field meets the minimum size requirement of 46 bytes.
  28. proxy ARP
    Process that uses the same ARP messages as normal ARP however a router replies instead of the host listed in the request.

    Router acts on behalf of the host to respond to the ARP request with the router's MAC address listed in the ARP reply so that the device can reach the intended host that it otherwise would not be able to reach.
  29. PAM
    Pulse Amplitude Modulation

    Form of signal modulation where the message information is encoded in the amplitude of a series of signal pulses.

    Transmits data by varying the amplitudes (voltage/power levels) of the individual pulses.

    Obsolete: replaced by PCM (Pulse Code Modulation)
  30. ROM
    Type of memory on which data has been prerecorded.

    Can not be removed - only read.
  31. RAM
    Main working area [temporary storage] used by the CPU for most processing and operations.

    Requires electrical power to maintain data storage. (Power turned off before saving - data is lost.)

    aka read-write memory
  32. runt frames
    Ethernet frame that is less than 64 bytes in size

    Caused by collisions

    • aka collision fragments
    • { minimum frame size = 64 bytes }
  33. selective forwarding
    Decisions to forward packets are made dynamically, hop by hop based on conditions on downstream nodes.
  34. store & forward
    Internal processing by LAN switches.

    Switch must receive the entire frame before it sends the first bit of the frame.

    (Cisco switches)
  35. switch table
    Associates MAC addresses with their corresponding port.

    see also bridge table.
  36. synchronous
    Communication that uses a common clocking signal.

    One of the communicating devices generates a clock signal into the circuit - additional timing info is not required in the header.
  37. slot time
    Minimum time a NIC or interface can take to send an entire frame.

    Slot time, then implies a minimum frame size.
  38. Thicknet
    Common term for 10BASE5 Ethernet.

    Thicker than 10BASE2 coax cable used for Thinnet.
  39. Thinnet
    Common term for 10BASE2 Ethernet.

    Thinner than 10BASE5 cable for Thicknet.
  40. transparent bridging
    Device learns source addresses of incoming frames and adds them to the bridging table (switch table, etc.)

    For forwarding frames received on one of the interfaces.
  41. UAA
    Universally Administered Address

    • aka
    • BIA - burned in Address
    • MAC Address
  42. VoIP
    Voice data encapsulated in an IP packet that allows it to traverse already implemented IP networks w/o needing its own network infrastructure.
  43. VLAN
    Network of computers that behave as if they are connected to the same network segment - even if they are located on different segments of a LAN.

    • Configured through software on the switch and router.
    • (IOS on Cisco routers/switches)