13868556
Descripción
Test por CSSE150(1,2,3) 5stream IITU, actualizado hace más de 1 año
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Creado por CSSE150(1,2,3) 5stream IITU
hace alrededor de 6 años
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Pregunta 1
Pregunta
Layers four and five of the Internet protocol stack are implemented in the end systems but not in the routers in the network core.
Respuesta
-
True
-
False
Pregunta 2
Pregunta
With ADSL, each subscriber gets more downstream bandwidth than upstream bandwidth.
Respuesta
-
True
-
False
Pregunta 3
Pregunta
Twisted-pair cooper wire is no longer present in computer networks.
Respuesta
-
True
-
False
Pregunta 4
Pregunta
4. Two packets A and B are sent in that order through a connection-oriented communication network. They could arrive at the destination:
Respuesta
-
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.
Pregunta 5
Pregunta
5. Two packets A and B are sent in that order through a connectionless communication network. They will arrive at the destination:
Respuesta
-
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.
Pregunta 6
Pregunta
6. The Internet received its name in the 1980s because:
Respuesta
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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.
Pregunta 7
Pregunta
DNS lookups often involve a combination of recursive and iterative queries.
Respuesta
-
True
-
False
Pregunta 8
Pregunta
The Date: header in the HTTP response message indicates when the object in the response was last modified.
Respuesta
-
True
-
False
Pregunta 9
Pregunta
Skype relay nodes are typically peers under the control of Skype users.
Respuesta
-
True
-
False
Pregunta 10
Pregunta
The process that sends messages into, and receives messages from, the network through a software interface is called a socket.
Respuesta
-
True
-
False
Pregunta 11
Pregunta
In a P2P File Distribution architecture, the server must sequentially send (upload) file copies.
Respuesta
-
True
-
False
Pregunta 12
Pregunta
12. SMTP is used to:
Respuesta
-
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.
Pregunta 13
Pregunta
13. Suppose a DNS resource record has Type=MX. Then:
Respuesta
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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.
Pregunta 14
Pregunta
14. Local DNS name servers:
Respuesta
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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.
Pregunta 15
Pregunta
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.
Respuesta
-
True
-
False
Pregunta 16
Pregunta
The size of the TCP RcvWindow never changes throughout the duration of the connection.
Respuesta
-
True
-
False
Pregunta 17
Pregunta
17. When a TCP segment arrives to a host, the socket to which the segment is directed depends on
Respuesta
-
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.
Pregunta 18
Pregunta
18. UDP has which of the following characteristics:
Respuesta
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a. regulated send rate.
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b. connection state at the server.
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c. three-way hand shake for connection establishment.
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d. none of the above.
Pregunta 19
Pregunta
19. When a UDP segment arrives to a host, in order to direct the segment to the appropriate socket, the OS uses:
Respuesta
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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.
Pregunta 20
Pregunta
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:
Respuesta
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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.
Pregunta 21
Pregunta
21. Streams are not needed in which of the following programs:
Respuesta
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a. TCPserver.
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b. UDPserver.
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c. TCPclient.
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d. UDPclient.
Pregunta 22
Pregunta
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
Respuesta
-
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.
Pregunta 23
Pregunta
For BitTorrent, which of the following is true:
Respuesta
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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.
Pregunta 24
Pregunta
24. Consider the latency model for dynamic congestion windows. Which of the following components contribute to latency?
Respuesta
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a. the sum of all the stalled times.
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b. round trip time, RTT.
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c. the transmission time of the object, O/R.
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d. all of the above.
Pregunta 25
Pregunta
25. TCP applies fast retransmit to a segment when:
Respuesta
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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.
Pregunta 26
Pregunta
26. Nmap is often used to:
Respuesta
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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.
Pregunta 27
Pregunta
27. With SYN cookies, when a server receives a SYN segment, it returns a SYNACK with:
Respuesta
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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.
Pregunta 28
Pregunta
Before sending a packet into a datagram network, the source must determine all of the links that packet will traverse between source and destination.
Respuesta
-
True
-
False
Pregunta 29
Pregunta
The primary role of a router is to forward datagrams from input links to output links.
Respuesta
-
True
-
False
Pregunta 30
Pregunta
Forwarding involves transferring a packet from the router’s input link to the appropriate output link.
Respuesta
-
True
-
False
Pregunta 31
Pregunta
All link layer protocols that support IP have the same frame structure (i.e., length of frame,
number and length of header fields).
Respuesta
-
True
-
False
Pregunta 32
Pregunta
CRC error detection, as used in Ethernet, is always able to detect whether there is an error in a frame.
Respuesta
-
True
-
False
Pregunta 33
Pregunta
The even parity bit scheme can correct single bit errors.
Respuesta
-
True
-
False
Pregunta 34
Pregunta
With CDMA, each sender uses the same code, cm, m=1,...,M.
Respuesta
-
True
-
False
Pregunta 35
Pregunta
Each LAN adapter has a unique LAN address.
Respuesta
-
True
-
False
Pregunta 36
Pregunta
41. A channel partitioning protocol has which of the following characteristics forwarding table is:
Respuesta
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a. it does not generate collisions.
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b. all transmitting nodes get the same amount of bandwidth.
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there is no master node.
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d. all of the above.
Pregunta 37
Pregunta
42. In slotted ALOHA with N active nodes, the probability that no node transmits in a given slot is
Respuesta
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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
Pregunta 38
Pregunta
43. An ARP query packet is encapsulated in
Respuesta
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a. an IP datagram.
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a link-layer frame addressed to a specific adapter.
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a link-layer broadcast frame.
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none of the above.
Pregunta 39
Pregunta
Ethernet provides which of the following services to the network layer
Respuesta
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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.
Pregunta 40
Pregunta
45. For Ethernet, if an adapter determines that a frame it has just received is addressed to a different adapter
Respuesta
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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.
Pregunta 41
Pregunta
A typical "infrastructure network" wireless network includes base stations.
Respuesta
-
True
-
False
Pregunta 42
Pregunta
In CDMA, the chipping rate is typically the same as the original data rate.
Respuesta
-
True
-
False
Pregunta 43
Pregunta
The 11 channels in the 802.11 are non-overlapping.
Respuesta
-
True
-
False
Pregunta 44
Pregunta
If you enter an Internet café and more than one AP is present, then the packets your host
Respuesta
-
True
-
False
Pregunta 45
Pregunta
During the 802.11 association handshake protocol, the wireless host gets assigned an IP address.
Respuesta
-
True
-
False
Pregunta 46
Pregunta
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:
Respuesta
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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.
Pregunta 47
Pregunta
52. A beacon frame sent by an AP includes
Respuesta
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a. the AP's SSID.
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b. the AP's MAC address.
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c. both the AP's MAC address and SSID.
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d. none of the above.
Pregunta 48
Pregunta
53. The 802.11 protocol does not implement collision detection because (Click all that apply)
Respuesta
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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.
Pregunta 49
Pregunta
54. Packets sent by two stations in 802.11 can collide because
Respuesta
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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.
Pregunta 50
Pregunta
An 802.11 frame includes:
Respuesta
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a. an acknowledgement field.
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b. a sequence number field.
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c. four address fields.
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d. all of the above.
Pregunta 51
Pregunta
In IP spoofing, the attacker interchanges the source and destination addresses in the sender's IP datagram.
Respuesta
- True
- False
Pregunta 52
Pregunta
Nonce's are often used to combat the playback attack.
Respuesta
-
True
-
False
Pregunta 53
Pregunta
65. Filtering in a firewall can be based on:
Respuesta
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a. source and destination IP addresses
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b. TCP ACK bits
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c. source and destination port numbers
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d. all of the above
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