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清華大學磨課師課程_2015電腦網路概論_課程第1週小考：網路架構與七層參考模式簡介
【 複選題 】(10%)
Which of the following are “internet applications” ?
(A) Wechat
(B) Routers
(C) Facebook
(D) Line
(E) Routing Protocols
【 複選題 】(10%)
Which of the following statements are correct for “links” of a
network?
(A) A “point-to-point” link is a link to connect two devices or hosts.
(B) A “point-to-point” link is a link to connect more than two devices or
hosts.
(C) A “multiple access” link is a link to connect multiple devices or
hosts.
(D) A “multiple access” link is a link to connect only two devices or
hosts.
(E) The IEEE 802.11 wireless LAN (WiFi) is a point-to-point link.
【 複選題 】 (10%)
Which of the following statements are correct for the “physical
layer” ? (多選)
(A) Transmit the data received from “data link layer” into the physical
channel.
(B) Encoding the data before transmitting them into the physical channel.
(C) The encoding schemes for different physical media are all the same.
(D) The encoding schemes for different physical media may be different.
(E) The physical layer also determines when to transmit the data.
【 複選題 】 (10%)
Which of the following statements are correct for
“store-and-forward” concept ?
(A) It’s a way for a network device to handle an incoming packet by
storing the packet first and then forwarding the packet according to some
switching/routing policy.
(B) A router usually stores an incoming packet in the memory first and
then lookups the MAC address table to determine which port to forward the
packet.
(C) A layer 2 switch usually stores an incoming frame in the memory first
and then lookups the IP routing table to determine which port to forward
the frame.
(D) A layer 2 switch usually stores an incoming frame in the memory first
and then lookups the MAC address table to determine which port to forward
the frame.
(E) The store-and-forward technology is usually NOT used in a packet
switched network.
【 複選題 】(10%)
Which of the following statements are correct for delivering packets
(datagrams) over the Internet ?
(A) A packet may be partitioned into several small packets by routers.
(B) The routing path of a packet is determined first before the packet is
sending into the Internet.
(C) The Internet is unreliable so that packets may be dropped or discarded
by routers due to traffic congestion.
(D) All packets destined to the same destination will be forwarded along
the same routing path.
(E) All fragments of a packet will be forwarded along the same path to the
destination.
【 單選題 】 (10%)
Which of the following statements are correct for “statistical
multiplexing” ?
(A) Compared to TDM (Time-Division-Multiplexing) and FDM
(Frequency-Division-Multiplexing), the statistical multiplexing provides
the same link utilization
(B) Data are transmitted only based on the arrival time of each flow.
(C) The bandwidth used by different flows is the same.
(D) The statistical multiplexing is fair due to the bandwidth used by
different flows are the same.
(E) Data are transmitted based on “demand” of each flow. Thus, the
bandwidth used by different flows may be different.
【 複選題 】(10%)
Which of the following statements are correct to describe the
“packet encapsulation” ?
(A) For sending node, the data from application level will be encapsulated
larger and larger until to the physical level.
(B) For receiving node, the data from physical level will be decapsulated
smaller and smaller until to the application level.
(C) The IP datagram is encapsulated into the TCP segment. That’s the TCP
protocol treats the IP datagram as data.
(D) The IP datagram is encapsulated into the underlying MAC frame. That’s
the MAC protocol treats the IP datagram as a data.
(E) For a router, it first uses decapsulation scheme to get a TCP segment
from the receiving port, and then uses encapsulation scheme to transmit
the TCP segment.
【 複選題 】(10%)
We say that a device is a “layer 2” device if it implements only
data link layer protocol and physical layer protocol. Which of the
following devices are usually layer 2 devices ? (多選)
(A) Hubs
(B) Bridges
(C) Load Balancers
(D) Routers
(E) Switches
【 單選題 】 (10%)
The “transmission time” of a network interface (card) to transmit a
packet is defined as “packet size/bandwidth”. For a 10Mbps Ethernet
interface, what is the transmission time to transmit a packet of size
1Kbytes ? (note that 1 byte = 8 bits) (單選)
(A) 8 ms
(B) 40 ms
(C) 80 ms
(D) 400 ms
(E) 800 ms
【 單選題 】 (10%)
The channel between a pair of processes can be viewed as a pipe.
Delay x Bandwidth means how many data can be stored in the pipe. For a
pipe with a delay of 400 ms and bandwidth of 100 Mbps, how many data can
be stored in the pipe ? (Mbps = Mega bits per second, and MB = Mega Byte =
106 bytes)
(A) 0.5 MB
(B) 1 MB
(C) 5 MB
(D) 10 MB
(E) 50 MB
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