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87 Cards in this Set
- Front
- Back
The (most complex) data unit used by Ethernet is?
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Frame
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In Ethernet, the transmitting wires are?
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1 and 2
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In Ethernet, the receiving wires are?
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3 and 6
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How would you recognize a straight-through Ethernet cable?
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Each connector would have the same colored pins in the same place.
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Why is twisted pair used for Ethernet cabling?
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Having the wires in a twisted pair reduces electrical interference.
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In UTP Ethernet, which pairs of wires are twisted together?
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Both sending wires are twisted together, as are both receiving wires.
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What does UTP stand for?
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Unshielded Twisted Pair
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What are the four functions generally performed by the Data Link Layer?
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Arbitration, Addressing, Error detection, and Identification
(note about Identification, it is unusual for a layer to be able to read the header from the layer above it. look into this) |
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What is the name of the algorithm used by Ethernet for Arbitration (prevention of collisions)?
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CSMA/CD
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What does CSMA/CD stand for?
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Carrier Sense Multiple Access with Collision Detection
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What is the type of address used by the Ethernet Data Link layer?
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MAC Address
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What is the type of address used by the Frame Relay Data Link layer?
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DLCI
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What does the MAC in MAC Address stand for?
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Media Access Control
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Error detection by the Data Link layer is performed by sending additional data such as ____?
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CRC or FCS
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What does CRC stand for?
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Cyclical Redundancy Check
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What does FCS stand for?
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Frame check sequence
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T/F: The Ethernet Data Link layer performs error detection and recovery.
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F: only detection
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The data link layer's Identification function is used to determine what?
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What protocol the data received should be passed to.
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What is a reason for the Identification function of the data link layer?
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Multiple protocols being used on a computer. For instance, IPX and TCP/IP.
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In DIX Ethernet, the DIX stands for?
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DEC, Intel, Xerox
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The IEEE spec 802.3 refers to what?
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Ethernet MAC sublayer
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The IEEE spec 802.2 refers to what?
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Ethernet LLC sublayer (also Token Ring and ANSI FDDI LLC sublayers)
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Early 10BASE2 and 10BASE5 networks lacked what common features of modern Ethernet?
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Hubs, switches. (probably routers?)
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A repeater is considered to operate at what layer of the OSI model?
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Physical
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T/F: A repeater operates by amplifying the signal it receives.
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False. It interprets the bits and generates a new signal to avoid repeating noise.
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T/F: 10BASE-T allowed the use of telephone cabling to be used as an Ethernet network.
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True
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The hubs used in 10BASE-T networks functioned as ______ repeaters.
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Multiport
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Hubs used in 10BASE-T networks take the signal received on one port and do what?
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Broadcast it to every port.
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A major weakness of 10BASE5 and 10BASE2 which was fixed by 10BASE-T?
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10BASE-T star topology made it so a break at one point would not cause the entire network to go down.
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10BASE-T has a _____ physical topology, but a _____ logical topology.
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star, bus
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What is one major impact of 10BASE-T with hubs using an electrical bus topology?
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Each computer shares the bandwidth of the network. 10 computers have a total bandwidth of 10Mbps
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What type of Ethernet cable is typically used to connect a computer to a hub? (Straight-through or crossover)
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Straight-through
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Hubs generally receive and send data on the (same/opposite) pins as a PC's network card?
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Opposite
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In order to connect a PC to a PC, or a hub to a hub, you would use what type of cable?
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Crossover
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An Ethernet cable between two hubs or switches is often called a ______.
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Trunk
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Definition of half-duplex?
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once a party begins receiving a signal, it must wait for the transmitter to stop transmitting, before replying
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Definition of full-duplex?
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allows communication in both directions, and, unlike half-duplex, allows this to happen simultaneously
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Land-line telephone networks are (half or full)-duplex?
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full-duplex
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What is a duplex communication system?
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two connected devices that can communicate with one another in both directions
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What is the purpose of NIC's loopback function in detecting collisions? (in a half-duplex 10BASE-T with hubs)
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The signal is not going to be re-broadcast to the sending NIC by the hub, so the NIC loops its own signal back to its receiving wires, so if it detects a different signal as well, it can tell a collision is happening.
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What are two things which have improved Ethernet performance, relating to the reduction of collisions?
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LAN switching and full-duplex Ethernet
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What does the term "collision domain" mean?
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The set of devices for which their frames could collide.
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How do switches differ from hubs?
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They treat each individual port as a separate bus.
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What are memory buffers in switches used for?
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To hold incoming frames in case more than one is sent at a given time on the same bus, they can be sent in turn and the devices do not have to re-transmit.
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Switches operate at which layer of the OSI model?
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Data Link
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Hubs operate at which layer of the OSI model?
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Physical
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Hubs interpret data in what unit?
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Bit
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Switches interpret data in what unit?
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Frame
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What part of the original Ethernet specification made half-duplex communication a necessity?
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Having all computers on the same bus.
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What device made full-duplex Ethernet possible? How?
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Ethernet switches replacing hubs
Eliminated collisions / need for CSMA/CD |
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T/F: CSMA/CD is not used in Full-Duplex Ethernet
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True
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In order for Full-Duplex operation to work, the NIC must _______ its loopback circuitry.
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Disable
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MAC addresses can also be known as?
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Burned-in Address (BIA), Universally Administered Addresses (UAA), LAN addresses, or Ethernet addresses
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What does the term "group address" refer to in the context of Ethernet?
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addresses which identify more than one LAN interface card
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What are the two general categories of Ethernet group addresses?
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Broadcast address
AND Multicast address |
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What is the value of the "Broadcast address"
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FFFF.FFFF.FFFF
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What does the "Broadcast address" signify to the LAN?
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Every device on the LAN should process the frame.
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Multicasting over Ethernet is supported by which protocol?
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IP
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What is the significance of
0100.5exx.xxxx ?? |
It is the format of the MAC address used for multicasting.
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Ethernet framing defines what?
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How a string of binary numbers is interpreted.
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The IEEE 802.3 spec limits the data portion of a frame to ______ bytes?
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1500 bytes
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DSAP stands for?
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Destination Service Access Point
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What is the purpose of DSAP?
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It identifies the type of protocol header which follows the (Ethernet) Data-Link header.
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Where is the DSAP located?
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In the Ethernet Data-Link header.
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Why was the SNAP field introduced?
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They ran out of possible DSAP codes.
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Which DSAP value signifies that a SNAP field follows the 802.2 header?
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AA
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Where is the SNAP field located in an Ethernet frame?
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After the standard 802.2 header, before the data.
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What does SNAP stand for?
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Subnetwork Access Protocol
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What does SSAP stand for?
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Source Service Access Point
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The "Type" field from the original Ethernet specification was replaced by ________ and then by _______
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SSAP + DSAP, SNAP
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T/F: Ethernet + TCP/IP requires the use of SNAP headers.
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True
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Why does Ethernet + TCP/IP require the use of SNAP headers?
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There is no DSAP value for TCP/IP.
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Which function is performed by the FCS field in the Ethernet frame?
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Error-detection.
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The only type of Ethernet which does not use DSAP or SNAP is?
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DIX Ethernet
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IEEE spec 802.3u defines what standard?
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Fast Ethernet
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Fast Ethernet operates at what speed?
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100Mbps
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Autonegotiation in 802.3u Ethernet refers to?
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Devices deciding between 10Mbps and 100Mbps, and between half and full duplex.
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The IEEE spec 802.3z defines what?
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Gigabit Ethernet over optical cabling.
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The IEEE spec 802.3ab defines what?
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Gigabit Ethernet over electrical cabling.
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T/F Gigabit Ethernet retains the option to use CSMA/CD
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True
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True/False: Ethernet uses the same headers and trailers over 10Mbps, 100Mbps, and 1Gbps
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True
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What is the size of the SNAP field?
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2 bytes
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What is the size of the DSAP and SSAP fields?
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1 byte each
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What is the size of a MAC address?
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6 bytes
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Which part of a MAC address identifies the manufacturer of the device?
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The first half
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What does OUI stand for?
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Organizationally Unique Identifier
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What is the meaning of OUI? (not what it stands for)
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The part of a MAC address which is unique to the manufacturer of the device.
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