Question 1
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Layers four and five of the Internet protocol stack are implemented in the end systems but not in the routers in the network core.
Question 2
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With ADSL, each subscriber gets more downstream bandwidth than upstream bandwidth.
Question 3
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Twisted-pair cooper wire is no longer present in computer networks.
Question 4
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4. Two packets A and B are sent in that order through a connection-oriented communication network. They could arrive at the destination:
Answer
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a. in any order, after having traversed the same route.
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b. only in the order A-B, after possibly having traversed different routes.
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c. in any order, after possibly having traversed different routes.
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d. only in the order A-B, after having traversed the same route.
Question 5
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5. Two packets A and B are sent in that order through a connectionless communication network. They will arrive at the destination:
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a. in any order, after possibly having traversed different routes.
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b. in the order A-B, after having traversed the same route.
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c. in any order, after having traversed the same route.
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d. in the order A-B, after possibly having traversed different routes.
Question 6
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6. The Internet received its name in the 1980s because:
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a. it was an interim (temporary) design of what it later became, but the name stuck.
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b. it was meant to be a network internal to the United States Department of Defense.
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c. it consisted of many interconnected networks.
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d. it achieved international scope with the addition of the City University of London.
Question 7
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DNS lookups often involve a combination of recursive and iterative queries.
Question 8
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The Date: header in the HTTP response message indicates when the object in the response was last modified.
Question 9
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Skype relay nodes are typically peers under the control of Skype users.
Question 10
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The process that sends messages into, and receives messages from, the network through a software interface is called a socket.
Question 11
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In a P2P File Distribution architecture, the server must sequentially send (upload) file copies.
Question 12
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12. SMTP is used to:
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a. to transfer messages from one mail server to another.
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b. to transfer messages from mail server to a user agent.
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c. to define the format of message headers.
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d. all of the above.
Question 13
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13. Suppose a DNS resource record has Type=MX. Then:
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a. Value is the hostname of the DNS server that is authoritative for Name.
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Value is the IP address of the mail server that has the alias hostname Name.
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c. Value is the hostname of the mail server that has the alias hostname Name.
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d. none of the above.
Question 14
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14. Local DNS name servers:
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a. cache resource records, but discard them after a period of time that is on the order of a few days.
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b. cache resource records and never discard them.
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c. obtain resource records from Web caches.
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d. never cache resource records.
Question 15
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Consider an HTTP Web server using persistent connections. Suppose the server spawns a
separate process for each client that connects to the server. Then each of these spawned processes will have different server port numbers.
Question 16
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The size of the TCP RcvWindow never changes throughout the duration of the connection.
Question 17
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17. When a TCP segment arrives to a host, the socket to which the segment is directed depends on
Answer
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a. the source IP address of the datagram that encapsulated the segment.
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b. the destination port number.
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c. the source port number.
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d. all of the above.
Question 18
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18. UDP has which of the following characteristics:
Question 19
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19. When a UDP segment arrives to a host, in order to direct the segment to the appropriate socket, the OS uses:
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a. the source port number.
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b. the source IP address.
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c. the destination port number.
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d. all of the above.
Question 20
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20. Suppose a client sends an HTTP request message with the If-modified-since: header. Suppose the object in a server has not changed since the last time a client retrieved the object. Then the server will send a response message with the status code:
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a. 404 Not Found.
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b. 200 OK.
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c. 304 Not Modified.
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d. none of the above.
Question 21
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21. Streams are not needed in which of the following programs:
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a. TCPserver.
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b. UDPserver.
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c. TCPclient.
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d. UDPclient.
Question 22
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22. Consider the minimum time for P2P file distribution, as discussed in Section 2.6. Suppose the upload rate of the server is10 Mbps, the upload rates of all peers is 1 Mbps, and the download rates of all peers is 10 Mbps. Further suppose that there are 100 peers and the file is 100 million bits. The minimum distribution time is
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a. approximately 100 seconds.
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b. approximately 10 seconds.
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c. approximately 1 second.
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d. approximately 1000 seconds.
Question 23
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For BitTorrent, which of the following is true:
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a. Although a peer may have 50 concurrent TCP connections with other peers, at any given instant of time it sends data to less than 10 other peers.
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b. At a given instant of time, a peer A may upload to a peer B, even if peer B is not sending anything to A.
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c. Among the chunks that a peer does not have, the peer will request chunks that appear to be relatively rare in the torrent.
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d. All of the above.
Question 24
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24. Consider the latency model for dynamic congestion windows. Which of the following components contribute to latency?
Question 25
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25. TCP applies fast retransmit to a segment when:
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a. it estimates unusually large RTTs.
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b. it receives three ACKs for an earlier segment.
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c. the segment's timer expires.
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d. none of the above.
Question 26
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26. Nmap is often used to:
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a. do port scans over a range of ports at a target host.
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b. measure throughput between hosts.
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c. measure round-trip times between hosts.
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d. decipher encrypted traffic.
Question 27
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27. With SYN cookies, when a server receives a SYN segment, it returns a SYNACK with:
Answer
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a. an initial sequence number that is a hash of the IP addresses and port numbers in the SYN segment (as well as of other things).
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b. initial sequence number 1.
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c. a randomly chosen initial sequence number.
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d. none of the above.
Question 28
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Before sending a packet into a datagram network, the source must determine all of the links that packet will traverse between source and destination.
Question 29
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The primary role of a router is to forward datagrams from input links to output links.
Question 30
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Forwarding involves transferring a packet from the router’s input link to the appropriate output link.
Question 31
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All link layer protocols that support IP have the same frame structure (i.e., length of frame,
number and length of header fields).
Question 32
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CRC error detection, as used in Ethernet, is always able to detect whether there is an error in a frame.
Question 33
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The even parity bit scheme can correct single bit errors.
Question 34
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With CDMA, each sender uses the same code, cm, m=1,...,M.
Question 35
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Each LAN adapter has a unique LAN address.
Question 36
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41. A channel partitioning protocol has which of the following characteristics forwarding table is:
Question 37
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42. In slotted ALOHA with N active nodes, the probability that no node transmits in a given slot is
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a. (1-p)N
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b. (1-p)N
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c. pN
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d. 1-p
Question 38
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43. An ARP query packet is encapsulated in
Question 39
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Ethernet provides which of the following services to the network layer
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a. error detection.
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flow control.
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reliable data transfer.
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all of the above.
Question 40
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45. For Ethernet, if an adapter determines that a frame it has just received is addressed to a different adapter
Answer
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a. it discards the frame without sending an error message to the network layer.
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it discards the frame and sends an error message to the network layer.
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it sends a NACK (not acknowledged frame) to the sending host.
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it delivers the frame to the network layer, and lets the network layer decide what to do.
Question 41
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A typical "infrastructure network" wireless network includes base stations.
Question 42
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In CDMA, the chipping rate is typically the same as the original data rate.
Question 43
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The 11 channels in the 802.11 are non-overlapping.
Question 44
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If you enter an Internet café and more than one AP is present, then the packets your host
Question 45
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During the 802.11 association handshake protocol, the wireless host gets assigned an IP address.
Question 46
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51. In CDMA, let Ym be the received value in the mth mini-slot for some slot i. Let cm, m=1,...,M, be the sender's M code values. To determine the bit value the sender sent, the receiver:
Answer
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a. multiples Ym with the sum of the M code values.
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b. multiplies each Ym with the corresponding cm, sums the resulting values and divides by M.
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simply declares Ym as the sent value.
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d. none of the above.
Question 47
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52. A beacon frame sent by an AP includes
Question 48
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53. The 802.11 protocol does not implement collision detection because (Click all that apply)
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a. collision detection was found to be useless in wired Ethernet.
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b. the adapter would still not be able to detect all collisions due to hidden terminals.
c. it is costly to build wireless hardware that detects collisions.
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c. it is costly to build wireless hardware that detects collisions.
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d. all of the above.
Question 49
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54. Packets sent by two stations in 802.11 can collide because
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a. at a given time, the random backoff values of the two stations are the same.
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b. the packets are sent to different APs but on the same channel.
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c. the two stations could be hidden from each other.
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d. all of the above.
Question 50
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An 802.11 frame includes:
Question 51
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In IP spoofing, the attacker interchanges the source and destination addresses in the sender's IP datagram.
Question 52
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Nonce's are often used to combat the playback attack.
Question 53
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65. Filtering in a firewall can be based on: