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山东建筑大学试卷
至
学年 第 1
试卷类别：考试
题号
一
二
三
学期
；
四
课程名称
计算机网络 A
考试形式：闭卷 ；
共 4页
（本科）试卷
考试时间
五
120
B
分钟
总分
分数
注意：
1. 可以用英文答题，也可以用中文答题。
2. 答案请写在每种类型题目的答题区中！！！
一、 Multiple Choice(20 points, 2 points each problem)
答题区：
1．
6.
2.
7.
3.
8．
4.
9.
5.
10.
1、OSPF routing protocol typically runs over:
A. IP
B. TCP
C. UDP
D. none of the above
2、The transfer of an Web document from one host to another is:
A. loss-intolerant and time insensitive
B. loss-tolerant and time sensitive
C. loss-intolerant and time sensitive
D. none of the above
3、Consider sending a 999 byte datagram into a link that has an MTU of 500
bytes.
A. 2 fragments are created with offset field value 0, 500, respectively
B. 3 fragments are created with offset field value 0, 480,960,
respectively
C. 3 fragments are created with offset field value 0, 60,120, respectively
D. None of the above
4、Suppose an application generates chunks of 120 bytes of data every
second, and each chunk gets encapsulated in a TCP segment and then an IP
datagram(no options fields). What percentage of each datagram will contain
application data?
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A. 80%
B. 75%
C. 60%
D. 25%
5、We are sending a 30 Mbit MP3 file from a source host to a destination host.
Suppose there is only one link between source and destination and the link
has a transmission rate of 10 Mbps. Assume that the propagation speed is 2
* 108 meters/sec, and the distance between source and destination is
10,000 km. Also suppose that message switching is used, with the message
consisting of the entire MP3 file. How many bits will the source have
transmitted when the first bit arrives at the destination?
A. 1 bit
B. 30,000,000 bits C. 500,000 bits D. none of the above
6、In routing among ASs, which of the following issues dominants
A. policy
B. geographical distance between ASs
C. current congestion levels in the ASs
D. number of ASs traversed
7、An ARP query packet is encapsulated in
A. a link-layer frame addressed to a specific adapter
B. a link-layer broadcast frame
C. an IP datagram
D. none of the above
8、A taking-turns protocol has which of the following characteristics
A. there is no single point failure.
B. it does not generate collisions
C. there is no master node
D. all of the above
9、TCP has which of the following characteristics:
A. flow control
B. connection establishment
C. congestion control
D. all of the above
10、Which of the following statements is true?
A. A network adapter (NIC) is an autonomous unit.
B. In a distance-vector routing algorithm, each node has a map of the
entire network and determines the shortest path from itself to all other
nodes in the network.
C. An adapter’s MAC address has a flat structure and doesn’t change no
matter where the adapter goes.
D. none of the above
二、 Fill in the Blanks(24 points, 2 points each problem)
答题区：
山东建筑大学试卷
1、 ______ 、________ 、________、________
2、_________、________、__________
3、___________________________________________
4、_________________________、_____________________
5、___________、_________、___________、________
6、__________、___________、___________
7、_________
8、_________、___________
9、 ______、______
10、________________________、____________________
11、_______、_________、___________
12、________、_________、_________
1、As a packet travels from one node to the subsequent node along the path,
the packet suffers from several types of delays at each node along the path.
The most important of these delays are the _______delay, _______delay,
_________ delay, and _______delay.
2、The Internet mail system has three major components: _________ ,
_________________, and ______________________.
3 、 _______________________________________ is called transportlayer multiplexing and demultiplexing.
4 、 Computer networks that__________________________ are called
virtual-circuit networks; Computer networks that ___________________
are called datagram networks.
5、There are 4 components in router’s architecture. They are input ports,
________, output ports and _________. And ______connects the router’s
input ports to its output ports; _______ executes the routing protocols.
6、Historically, two routing protocols have been used extensively for routing
within an autonomous system in the Internet: RIP protocol and ________
protocol. And ______ is a distance-vector protocol. And _______ is a
link-state protocol.
7 、 TCP provides a _______service to its applications to eliminate the
possibility of the sender overwhelming the receiver..
8、We can classify just about any multiple access protocol as belonging to
one of three categories. CSMA/CD belongs to ________ protocol. Polling
belongs to ________ protocol.
9、A hub is a _____-layer device, and switches are _____-layer devices.
10、Cookie technology has four components: a cookie header line in HTTP
response message; a cookie header line in the HTTP request message;
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_____________________________; __________________.
11、Two basic approaches toward pipelined error recovery can be identified:
_______________and ____________. And in _______ protocol, the
receiver discards out-of-order-packets. .
12、There are two fundamental approaches to building a network core:
_____ switching and _____ switching. And in ____ switched networks, the
resources are not reserved; a session’s messages use the resources on
demand, and as a consequence, may have to wait for access to a
communication link.
三、 True or False(10 points, 1 point each problem)
答题区：
1、
6、
2、
7、
3、
8、
4、
9、
5、
10、
1、When a user request a Web page that consists of some text and two
images. For this page, the client will send one request message and receive
three response messages.
2、It is possible for a mail client to send e-mail messages over HTTP rather
than SMTP.
3、In TCP, the acknowledgement number that a host puts in a segment is the
sequence number of the next byte the host is expecting from the sender.
4、TCP applies fast retransmit to a segment when it estimates unusually
large RTT.
5、Local DNS name servers cache resource records, but discard them after
a period of time that is on the order of a few days.
6、For the Web application, the user agent is the user’s keyboard.
7、Suppose that host A wants to send data over TCP to host B, and host B
wants to send data to host A over TCP. Two separate TCP connections - one
for each direction - are needed.
8、When a TCP segment arrives to a host, the socket to which the segment
is directed depends on the source IP address of the datagram encapsulated
the segment，the source port number，the destination port number and the
destination IP address.
9、The stop-and-wait protocol is highly inefficient when there is a large
distance between source and destination and the transmission rate is high.
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10、Suppose a router has n input ports each with identical line speeds, n
output ports each with identical line speeds, and the line speed of an output
port is at least n times as that of an input port. Further suppose that the
switching fabric speed is at least n times as fast as an input line speed. Then
queuing can occur in an output port.
四、Answer the following questions briefly.(33 points)
4、
答题区：
1、
Mechanism
Timer
Sequence Number
Acknowledgment
2、
Negative ACK
Window, pipelining
Checksum
5、
3、
6、
Use
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convergence of a synchronous version of the distance vector algorithm.（8
points）
y
x
1、How many layers are there in the Internet protocol stack? What are they?
What are the principal responsibilities of each of these layers?(7 points)
2. What is the difference between persistent HTTP with pipelining and
persistent HTTP without pipelining? (4 points)
3. Consider a subnet with prefix 202.202.202.64/26. Give an example of
one IP address (of form xxx.xxx.xxx.xxx) that can be assigned to an
interface in this network. Suppose an ISP owns the block of addresses of the
form 202.202.202.64/26. And suppose it wants to create four subnets from
this block, with each block having the same number of IP addresses. What
are the prefixes (of form a.b.c.d/x) for the four subnets? (5 points)
4. In the table, there are six reliable data transfer mechanisms. Give the use
of each mechanism. (6 points)
2.Suppose two hosts, A and B, are separated by 10,000kilometers and are
connected by a direct link of R=1Mbps. Suppose the propagation speed
over the link is 2.5·108 meters/sec. Consider sending a file of 400,000 bits
from Host A to Host B.（5 points）
a) How long does it take to send the file, assuming it is sent
continuously?
b) Suppose now the file is broken up into 10 packets with each packet
containing 40,000bits. Suppose that each packet is acknowledged by the
receiver and the transmission time of an acknowledgment packet is
negligible. Finally, assume that the sender cannot send a packet until the
preceding one is acknowledged. How long does it take to send the file?
答题区：
1、
Mechanism
Timer
Sequence Number
Acknowledgment
Negative ACK
Window, pipelining
Checksum
Use
5. List six access technologies and classify each one as residential access,
company access, or mobile access. (6 points)
6. In CSMA/CD, after the sixth collision, what is the probability that a node
chooses K=3? The result K=3 corresponds to a delay of how many seconds
on a 10Mbps Ethernet? (5 points)
五、Computing Problems (13 points)
1、 Consider the network shown below, the link costs are c(x,y)=5, c(y,z)=6,
c(z,x)=2. Compute the distance tables after the initialization step and after
z
2、
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