(王世普)期中考试试卷(答案)
中国石拱桥-温州拦街福
云南大学2013至2014学年上学期软件学院2012级
《计算机网络原理》期中考试试卷（闭卷）答案
第一题答题卡：
小题号
回 答
1 2 3 4 5 6 7 8 9 10
D C D A
C A B B A B
第二题答题卡：
回 答
× ×
√ × ×
一、单项选择题（每个选项1分，共10分，请将选择结果填入第一题答题卡）
小题号
1 2 3 4 5
1．MIME allows （1）
data to be sent through SMTP.
（1）A．audio
B．non-ASCII C．image D．all of the above
2．A
JPEG image is sent as email ,What is the content-
type （2） .
（2）A．multipartmixed
C．imageJPEG
B．multipartimage
D．imagebasic
3．A user
want to send some information to Web server using
HTTP protocol, the request line
method is （3）
.
（3）A．GET B．PATCH C．MOVE D．POST
4． (
4 ) of the following fields is not part of the
UDP header fields.
（4）A．length of header
C．checksum
B．UDP source port number
D．UDP destination port number
5．PDU（Protocol Data Unit）at transport layer of
TCPIP model are called (5) , PDU at the
network layer are called (6) , and PDU at
the Link layer are called bit.
（5）A．Cell
B．division
C．segment
C．data
D．part
D．cell （6）A．datagram
B．program
6．A user requests a Web page that
consists of a basic HTML file and 3 JPEG image
files. d
trans
denoting the time to
transfer a file. The total time is ( 7 ) to
request the Web page in
persistent connections
mode?
（7）A. 4(2RTT+ d
trans
) B. 2RTT+4
d
trans
C. RTT+4 d
trans
D.4(RTT+
d
trans
)
7．TCP sender takes ( 8
) policy to decrease the waiting time resending
the missing segment
before the segment’s timer
expires.
（8）A. response timeout event
C.
Congestion control
B. Fast retransmit
D.
flow control
8．Host A sends a TCP segment (Seq
= 43, ACK = 103) to host B and Host B replies with
a TCP
segment (Seq = 103, ACK = 57). The
payload length of the TCP segment from host A to
host
B is ( 9 ) .
（9）A．14 bytes. B．43
bytes. C．46 bytes. D．57 bytes.
9． IP address
“4.5.6.7” is an ( 10 ) class address.
（10）A.
B class B. A class C. D class D. C class
二、判断正误（每个问题1分，共5分。正确的打“√”、错误的打“×”，请将判断结果填入第
二题答
题卡）
1. The DNS defines a distributed,
hierarchical database that provides only hostname
to IP address
mappings. (
×
)
2. The “Date:” header line in the
HTTP response message indicates when the object in
the
response message was last modified.
(
×
)
(
√
)
(
×
)
(
×
)
3．The receive window size
of GBN protocol is equal to 1.
4．The UDP
header checksum is recomputed at every routers.
5．Suppose that the last SampleRTT in a TCP
connection is equal to 1 sec. Then Timeout for the
connection will necessarily be set to a value
>= 1 sec.
三、回答下列问题（每个问题5分，共35分）
1．For a communication session between two
hosts, which host is the client and which is the
server?
要点：通信的发起者（请求者）是client；通信的接受者（响应者）是server
2．What is the difference between persistent
HTTP with pipelining and persistent HTTP without
pipelining?
要点：前者是一个TCP连接传输多个页面；后者是一个TCP连接传输一个
页面。
3．What are the two types of services that the
Internet provides to its applications? What are
important characteristics of each of these
services?
要点：面向连接的服务（连接管理、正确可靠、按序交互、流控
制、拥塞控
制）；无连接服务（不需建立连接、不可靠、每个报文独立传送，无流控制
和拥塞控
制）
4．List five non-proprietary (非私有的，指与厂商无关的)
Internet applications and the
application-
layer protocols that they use.
要点：Web应用（HTTP协
议）；文件传输（FTP协议）；电子邮件（SMTP、
POP3、IMAP协议）；远程登录（Tel
net协议）；域名服务（DNS协议）；
网络管理（SNMP协议）；实时传输（RTP协议）
5．Why is it said 带外的) that FTP sends control
information?
要点：使用一个单独的连接（辅助通道、控制连接）来传送FTP命令；数
据
传输单独一个连接（主通道、数据连接）。因其是在主通道（数据连接）之
外的通道，故称为
带外通道。
6．Please list the main transmission
mediums used in the computer network.
要点：电线（双绞线、同轴电缆、UTPSTP）、光纤、无线、卫星
7．What are
the differences Congestion Control and flow
control.
要点：范围不同（全网；通信双方）、目的不同（防止接收端缓冲区溢出；防
止网络拥塞）
四、计算题（共25分）
1． Suppose A sends two TCP
segments to B. The first segment has sequence
number 715; the
second has sequence number
1297. （5分）
(1) How much data is the first
segment?
(2) Suppose that the first segment is
lost, but the second segment arrives at B. In the
acknowledgement that B sends to A, what will
be the acknowledgment number?
答：（1）1297-715=582；（2）715
2． UDP and TCP
use 1's complement sum for their checksums.
Suppose you have the following
three 16-bit
words: 0101, 1001, 1111. What is the
1's
complement sum of these words? （10分）
答：1100
1011
0101
1001
1111
1111
11111
1
1100
3．Consider two hosts, Host A and B, connected
by a single link of rate R bps. Suppose that the
two hosts are separated by m meters, and
suppose the propagation speed along the link is s
meterssecond, and the size of packet is L
bits. （10分）
(1) Express the propagation
delay, d
prop
in terms of m and s.
d
prop
= ms
(2) Determine the
transmission delay d
trans
in terms L and
R.
d
trans
=LR
(3) If R=150Mbps,
m=100km, s=3
10
8
ms and L=1500bits,
please compute
：
d
prop
=ms=100=13000s=13ms
d
trans
=LR=15=1100000s=1100ms=10μs
五、综合题（共25分）
1．Match the following tasks to
one of the TCPIP layers: （7分）
(1) Transmission
of Data Segment
(2) ASCII
changed to EBCDIC
(3)
Transmission of data frame
( 传送层 )
( 应用层 )
( 链路层 )
(
应用层 )
( 网络层 )
( 传送层 )
( 应用层 )
(4) Provides log-in and
logout procedures
(5) Selects a
destination network
(6)
Provides services for the network applications
(7) Provides E-mail and file transfer services
2．How does TCP the connection provide the
flow-control service according the following
figure?
（8分）
要点：1、接收方将RcvWindow=RcvBuffer-[LastByteRcvd-Las
tByteRead]通过捎带确认或
单独确认包发送给发送方，发送方控制发出而未收到确认的数据总
量，使其不超过
RcvWindow；
3．The below figure
is the Selective-Repeat protocol’s sender and
receiver views of
sequence-number space.
(1) Please analyse what does the SR protocol
differ from the GBN protocol.
(2) Please
analyse what actions does the sender take when
(a) timeout event occurring;
(b) the
sender received ACK packet from the receiver?
（10分）
要点：
（1）窗口尺寸不同；定时方式不同（单独、最小）；超时重传
不同（单独、回
退重传）；接收缓冲不同；确认方式不同（单独、累计）
（2
）（a）重传超时的包；（b）标记对应的包为已确认的包；如果是窗口下沿的
包的确认，则推进窗口到
未被确认的序号最低的包。
云南大学2013至2014学年上学期软件学院2012级
《计算机网络原理》期中考试试卷（闭卷）答案
第一题答题卡：
小题号
回 答
1 2 3 4 5 6 7 8 9 10
D C D A
C A B B A B
第二题答题卡：
回 答
× ×
√ × ×
一、单项选择题（每个选项1分，共10分，请将选择结果填入第一题答题卡）
小题号
1 2 3 4 5
1．MIME allows （1）
data to be sent through SMTP.
（1）A．audio
B．non-ASCII C．image D．all of the above
2．A
JPEG image is sent as email ,What is the content-
type （2） .
（2）A．multipartmixed
C．imageJPEG
B．multipartimage
D．imagebasic
3．A user
want to send some information to Web server using
HTTP protocol, the request line
method is （3）
.
（3）A．GET B．PATCH C．MOVE D．POST
4． (
4 ) of the following fields is not part of the
UDP header fields.
（4）A．length of header
C．checksum
B．UDP source port number
D．UDP destination port number
5．PDU（Protocol Data Unit）at transport layer of
TCPIP model are called (5) , PDU at the
network layer are called (6) , and PDU at
the Link layer are called bit.
（5）A．Cell
B．division
C．segment
C．data
D．part
D．cell （6）A．datagram
B．program
6．A user requests a Web page that
consists of a basic HTML file and 3 JPEG image
files. d
trans
denoting the time to
transfer a file. The total time is ( 7 ) to
request the Web page in
persistent connections
mode?
（7）A. 4(2RTT+ d
trans
) B. 2RTT+4
d
trans
C. RTT+4 d
trans
D.4(RTT+
d
trans
)
7．TCP sender takes ( 8
) policy to decrease the waiting time resending
the missing segment
before the segment’s timer
expires.
（8）A. response timeout event
C.
Congestion control
B. Fast retransmit
D.
flow control
8．Host A sends a TCP segment (Seq
= 43, ACK = 103) to host B and Host B replies with
a TCP
segment (Seq = 103, ACK = 57). The
payload length of the TCP segment from host A to
host
B is ( 9 ) .
（9）A．14 bytes. B．43
bytes. C．46 bytes. D．57 bytes.
9． IP address
“4.5.6.7” is an ( 10 ) class address.
（10）A.
B class B. A class C. D class D. C class
二、判断正误（每个问题1分，共5分。正确的打“√”、错误的打“×”，请将判断结果填入第
二题答
题卡）
1. The DNS defines a distributed,
hierarchical database that provides only hostname
to IP address
mappings. (
×
)
2. The “Date:” header line in the
HTTP response message indicates when the object in
the
response message was last modified.
(
×
)
(
√
)
(
×
)
(
×
)
3．The receive window size
of GBN protocol is equal to 1.
4．The UDP
header checksum is recomputed at every routers.
5．Suppose that the last SampleRTT in a TCP
connection is equal to 1 sec. Then Timeout for the
connection will necessarily be set to a value
>= 1 sec.
三、回答下列问题（每个问题5分，共35分）
1．For a communication session between two
hosts, which host is the client and which is the
server?
要点：通信的发起者（请求者）是client；通信的接受者（响应者）是server
2．What is the difference between persistent
HTTP with pipelining and persistent HTTP without
pipelining?
要点：前者是一个TCP连接传输多个页面；后者是一个TCP连接传输一个
页面。
3．What are the two types of services that the
Internet provides to its applications? What are
important characteristics of each of these
services?
要点：面向连接的服务（连接管理、正确可靠、按序交互、流控
制、拥塞控
制）；无连接服务（不需建立连接、不可靠、每个报文独立传送，无流控制
和拥塞控
制）
4．List five non-proprietary (非私有的，指与厂商无关的)
Internet applications and the
application-
layer protocols that they use.
要点：Web应用（HTTP协
议）；文件传输（FTP协议）；电子邮件（SMTP、
POP3、IMAP协议）；远程登录（Tel
net协议）；域名服务（DNS协议）；
网络管理（SNMP协议）；实时传输（RTP协议）
5．Why is it said 带外的) that FTP sends control
information?
要点：使用一个单独的连接（辅助通道、控制连接）来传送FTP命令；数
据
传输单独一个连接（主通道、数据连接）。因其是在主通道（数据连接）之
外的通道，故称为
带外通道。
6．Please list the main transmission
mediums used in the computer network.
要点：电线（双绞线、同轴电缆、UTPSTP）、光纤、无线、卫星
7．What are
the differences Congestion Control and flow
control.
要点：范围不同（全网；通信双方）、目的不同（防止接收端缓冲区溢出；防
止网络拥塞）
四、计算题（共25分）
1． Suppose A sends two TCP
segments to B. The first segment has sequence
number 715; the
second has sequence number
1297. （5分）
(1) How much data is the first
segment?
(2) Suppose that the first segment is
lost, but the second segment arrives at B. In the
acknowledgement that B sends to A, what will
be the acknowledgment number?
答：（1）1297-715=582；（2）715
2． UDP and TCP
use 1's complement sum for their checksums.
Suppose you have the following
three 16-bit
words: 0101, 1001, 1111. What is the
1's
complement sum of these words? （10分）
答：1100
1011
0101
1001
1111
1111
11111
1
1100
3．Consider two hosts, Host A and B, connected
by a single link of rate R bps. Suppose that the
two hosts are separated by m meters, and
suppose the propagation speed along the link is s
meterssecond, and the size of packet is L
bits. （10分）
(1) Express the propagation
delay, d
prop
in terms of m and s.
d
prop
= ms
(2) Determine the
transmission delay d
trans
in terms L and
R.
d
trans
=LR
(3) If R=150Mbps,
m=100km, s=3
10
8
ms and L=1500bits,
please compute
：
d
prop
=ms=100=13000s=13ms
d
trans
=LR=15=1100000s=1100ms=10μs
五、综合题（共25分）
1．Match the following tasks to
one of the TCPIP layers: （7分）
(1) Transmission
of Data Segment
(2) ASCII
changed to EBCDIC
(3)
Transmission of data frame
( 传送层 )
( 应用层 )
( 链路层 )
(
应用层 )
( 网络层 )
( 传送层 )
( 应用层 )
(4) Provides log-in and
logout procedures
(5) Selects a
destination network
(6)
Provides services for the network applications
(7) Provides E-mail and file transfer services
2．How does TCP the connection provide the
flow-control service according the following
figure?
（8分）
要点：1、接收方将RcvWindow=RcvBuffer-[LastByteRcvd-Las
tByteRead]通过捎带确认或
单独确认包发送给发送方，发送方控制发出而未收到确认的数据总
量，使其不超过
RcvWindow；
3．The below figure
is the Selective-Repeat protocol’s sender and
receiver views of
sequence-number space.
(1) Please analyse what does the SR protocol
differ from the GBN protocol.
(2) Please
analyse what actions does the sender take when
(a) timeout event occurring;
(b) the
sender received ACK packet from the receiver?
（10分）
要点：
（1）窗口尺寸不同；定时方式不同（单独、最小）；超时重传
不同（单独、回
退重传）；接收缓冲不同；确认方式不同（单独、累计）
（2
）（a）重传超时的包；（b）标记对应的包为已确认的包；如果是窗口下沿的
包的确认，则推进窗口到
未被确认的序号最低的包。