CS 228 Networking Test #1

  1. A computer network is
    1. Just the software that connects computers.
    2. Transmits analog and digital data.
    3. Only transmits digital data (or analog data in digital form).
    4. None or all of the above are true.
  2. Bandwidth is
    1. The rate at which a computer net can accept and deliver data.
    2. The time it takes to get data from source to destination.
    3. The accuracy with which a network transmits data (error rate).
    4. The likelyhood that a computer network will be up and functional at any needed time.
    5. All or none of the above.
  3. Latency is
    1. The rate at which a computer net can accept and deliver data.
    2. The time it takes to get data from source to destination.
    3. The accuracy with which a network transmits data (error rate).
    4. The likelyhood that a computer network will be up and functional at any needed time.
    5. All or none of the above.
  4. Availability is
    1. The rate at which a computer net can accept and deliver data.
    2. The time it takes to get data from source to destination.
    3. The accuracy with which a network transmits data (error rate).
    4. The likelyhood that a computer network will be up and functional at any needed time.
    5. All or none of the above.
  5. (True/False) Baud is the number of bits a network connection can carry per unit time.
  6. (Half/Full) duplex means that the link cannot carry data in both directions at once.
  7. Please write a formula that tells how long a packet needs to go from a source to a destination.  You may use the variables SIZE, LATENCY, and BANDWIDTH.

    8. ________________________________________________________________

    General Layering Questions

  8. Why do we use layering in network design?

    9. _______________________________________________________________
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  9. As a general rule, how much data does the lower layer send in comparision to the upper layers.
    1. More
    2. Same
    3. Less
  10. Connect the columns with lines.
    11. Layer Function
    Data Link Describes wire connections and volts
    Physical Routes data between nodes.  Controls congestion and such.
    Network Offers reliable datagrams to higher layers

    Classes of Communication Services

  11. An example of an asynchronus service is
    1. A file server transfering data.
    2. A print server printing a file.
    3. A web server offering web pages.
    4. All or none of the above.
  12. Synchronus data services ...
    1. Can handle data with no fixed maximum arival rate.
    2. Might corrupt or loose data in transit.
    3. Always sends data as single packets, and has no idea of connections.
    4. All or none of the above.
  13. The central most important concept with expidited data
    1. Is data that cannot tollerate corruption.
    2. Is data that cannot tollerate latency variation or latency jitter.
    3. Is data that the sender wants to arrive out of order with respect to other data in the stream (connection).
    4. All or none of the above.
  14. On demand video is an example of
    1. Asynchronus data.
    2. Synchronus data.
    3. Expidited data.

    Physical Layer

  15. Signals (light or electrical) move thru cable at what speed?
    1. Speed of light (300,000km/sec).
    2. Speed of light in the cable (200,000 km/sec in copper).
    3. Speed of sound (750 miles/hour in a standard atmosphere).
    4. None or all of the above.
  16. Why do the wires twist in twisted pair?
    1. They don't really, that's just the name.
    2. Twisting the wires reduces crosstalk and other forms of radio interfeerence.
    3. Twisting the wires makes them physically stronger and less prone to breakage.
    4. Twisting the wires makes them shorter for a given distance.

    ALOHA

  17. What happens if two stations transmit at the same time?
    1. The signal becomes garbled and no station is understood.
    2. The stronger/closer station dominates and is understood.
    3. The weaker station hears the stronger station and backs off.
    4. All or none of the above.
  18. What is the difference betweeen pure and slotted aloha?
    1. Pure aloha uses packets of a fixed length.
    2. Slotted aloha uses packets of a fixed length.
    3. Pure aloha allows transmissions to start at any time.
    4. Slotted aloha allows transmissions to start at any time.
  19. Why does aloha use a random timer for delay after collsions.
    1. All or none of the below.
    2. To allow any station not in the collsion a chance to transmit.
    3. To rest and cool the transmitters after use.
    4. So stations are less likely to recollide.
  20. Which has a higher theoretical maximum effeciency?
    1. Slotted aloha.
    2. Pure Aloha.
    3. They are equal.
  21. Which statement is most true of rippled aloha?
    1. Oh lord, won't ya buy me a Merceded Benz?
    2. My friends all drive Porches; I must make amends.
    3. Worked hard all my lifetime; no help from my friends.
    4. Oh Lord, won't ya buy me a Mercedes Benz?
    5. All or none of the above.

    Ethernet

  22. Ethernet
    1. Is a physical layer protocol.
    2. Is a data link layer protocol.
    3. Is both.
    4. Is neither.
  23. (True/False) Ethernet handles collsions just like pure aloha.
  24. (True/False) Every collsion in an ethernet has an equal chance of getting a long random delay.
  25. (True/False) A correctly formed ethernet packet has a CRC error correcting code on it
  26. (True/False) ARP is a protocol used to determine an internet IP address given an internet host name.
  27. (Aloha/Ethernet) Which has a better effeciency, slotted aloha or ethernet?
  28. What is the maximum latency before a node can access the ethernet?
    1. Twice the propogation delay across the cable.
    2. Twice the propgation delay accross the cable plus the length of time needed to transmit a maximum size packet.
    3. Infinite
    4. 28 ms.

    Token Ring andToken Bus

  29. (True/False) If there is no token on the token ring for a long time, a new master station must be elected.
  30. When can a station transmit without the token?
    1. When it wants to enter the ring.
    2. When it has top priority data to transmit.
    3. When it wants to leave the ring.
    4. NEVER!!!!!
    5. None or all of the above.
  31. (True/False) Token ring has a priority scheme that ensures high priority data gets sent first.
  32. In token bus, a new node can enter the bus
    1. After is acquires the token.
    2. When a node sends an "I WANT OUT" packet.
    3. When a node sends a "SOLICIT A SUCCESSOR" packet.
    4. When the master station sends a "JOIN THE RING" token.

    Alternating Bit, Selective Repeat, and Go Back N

  33. These three protocols are in what layer?
    1. Physical layer
    2. Data link layer
    3. Network Layer
    4. All or none of the above
  34. When is alternating bit protocol particularly bad and ineffecient?
    1. With small packet sizes and low latencies
    2. With small packet sizes and high latencies
    3. With large packet sizes and low latencies
    4. With large packet sizes and high latencies.
  35. Say that with selective repeat and a window size of 8, you the receiver just received packet number 4.  Which of these are possible.
    1. Packet #4 is a duplicate of a packet you successfully received in the past.
    2. Packet #4 is new data you never had before.
    3. Both #1 and #2.
    4. Neither #1 nor #2.
  36. When is Go Back N just as good as selective repeat?
    1. When latency is low and packet size high.
    2. When there is lots of room for packet buffer space.
    3. When latency is high and packet size small.
    4. When there are no errors.