C.) RPC D.) File
141.Which one represents a correct HTML tag for form?
A.) <form ACTION=”http://www.intel.com/cgi-bin/scpu” type=radio method=get>
B.) <form ACTION=”http://www.intel.com/cgi-bin/scpu” type=text method=put >
C.) <form ACTION=”http://www.intel.com/cgi-bin/scpu” method=post >
D.) <form ACTION=”http://www.intel.com/cgi-bin/scpu” method=push >
142.Client-side dynamic web page generation may use following technologies:
JavaScript, Java applet, Activex control. Which of the following statements is incorrect?
A.) JavaScript programs have the best portability among them.
B.) JavaScript programs are easier to write.
C.) Java applets execute faster.
D.) ActiveX controls run faster of all.
143.When a user clicks on a hyperlink, http://www.zju.edu.cn/lib/index.html, the browser carries out a series of steps in order to fetch the page pointed to.
Which one is not in these steps?
A.) The browser determines the URL
B.) The browser asks DNS for the IP address of www.zju.edu.cn C.) The browser sends a UDP request asking for file /lib/index.html D.) The browser displays all the text in index.html
144.A cookie may contain five fields, Which one is not in these fields？
A.) The domain field which indicates the server’s domain name.
B.) The path field that identifies which parts of the server’s file tree may use the cookie.
C.) The expire field that specifies when the cookie expires.
D.) The protocol field that specifies what protocol is used.
145.Common Gateway Interface(CGI) is a standardized interface to allow Web Server
to talk to back-end programs and scripts, this Web Server sends pages to browser.
A.) active
B.) form C.) dynamic D.) static
========================== network security ==============================
146.The purpose of is to prevent adversary from modifying or altering information.
A.) secrecy B.) authentication
C.) Integrity control D.) nonrepudiation
147.In each letter or group of letters is replaced by another letter or group of letters to disguise it.
A.) Transposition Cipher B.) substitution cipher C.) SHA-1
D.) MD5
148.________ is based on Galois field theory, it uses substitution, permutations, and multiple rounds of calculations.
A.) DES B.) AES C.) MD5 D.) RSA
149.The Diffie-Hellman key exchange protocol allows two strangers to establish a shared secret key; however, it can be defeated by .
A.) bucket brigade attack B.) reflection attack C.) denial of service
D.) attack of electronic code book mode
150.Various schemes have been devised for digital signatures, using both symmetric-key and ________-key algorithms.
A.) one time B.) private C.) public D.) session
三、 (21 points) In a TCP/IP network, an original IP datagram contains 1500 bytes of data (i.e. payload) and 36 bytes of header. When it passes through a router with the maximum datagram length (header + data) of 420 bytes, it breaks into multiple fragments. In the format (header length, total length, Identification, DF,MF, offset ), the values of original datagram’s header fields are (9,1536,13762,0,0,0).
(1). The original datagram breaks into fragments, the length of the first fragment’s data part is bytes, and the length of the last one’s data part is bytes.
(2). Please fill these fragment’s header field values with the format
(header length, total length, Identification, DF,MF, offset ) in following blanks:
the first fragment: , , , , , the second fragment: , , , , ,
the last fragment: , , , , , answer: (1). The original datagram breaks into 4 fragments, the length of the first fragment’s data part is 384 bytes, and the length of the last one’s data part is 348 bytes.
(2). Please fill these fragment’s header field values in a format
(header length, total length, Identification, DF,MF, offset ) in following blanket:
1# fragment （9，420，13762，0，1，0）
2# fragment （9，420，13762，0，1，48）
4# fragment （9，384，13762，0，0，144）
四、 (10 points) Consider building a CSMA/CD network running at 100 Mbps over a 800-m cable without repeater. The signal speed in the cable is 200,000 km/sec, and station A and B are located in the two end of the cable.
Please fill values in following blanks.
(1). The time to transmit 1 byte is noted as T, T = __(1)___ s, a frame can run __(2)___ meters along the cable in interval T.
(2). The round trip time between A and B is ___(3)__ s, the minimum frame size should be ___(4)__ bytes.
(3). If the data rate becomes 1 Gbps and the cable length becomes 200 meters, the minimum frame size should be ___(5)__ bytes.
===============================
answer (1). The time to transmit 1 byte is noted as T, T = _0.08_ s, a frame can run __16__ meters along the cable in interval T.
(2). The round trip time between A and B is __8_ s, the minimum frame size should be __100__ bytes.
(3). If the data rate becomes 1 Gbps and the cable length becomes 200 meters, the minimum frame size should be __250__ bytes.
五、 (9 points) HDLC and TCP are different protocols, some features are discussed as follows, please choose appropriate word from the optional words list and fill it in the blank.
(1). The sending sequence number of HDLC PDUs increments by 100 when 100 ______(1)________ are sent, while the sending sequence number of TCP PDUs increments by 100 when 100 ______(2)_________ are sent.
(2). HDLC’s sending window uses a ______(3)_______ value; TCP’s sending window uses a ______(4)_______ value which is determined by the header field “______(5)_________ ” of the TCP segment sent by receiver.
(3). TCP uses _______(6)_______ handshake to establish a connection. Some segment’s flag bit ______(7)________ is set to 1 during the period of connection establishment.
(4). In TCP, when receiver sends a PDU with its field _______(8)________ set to 0, the sender should stop sending data; In HDLC, when receiver sends a PDU with its field type set to 2 which stands for _______(9)_______ , the sender should stop sending data.
The optional words are listed as follows:
FIN, RECEIVE-NOT-READY, window-size, SYN, REJECT, bytes, datagrams, fixed, three-way, segments, RESET, two-way, variable, messages, frames, URG
Answer:
(1). The sending sequence number of HDLC PDUs increments by 100 when 100 frames are sent, while the sending sequence number of TCP PDUs increments by 100 when 100 bytes are sent.
(2). HDLC’s sending window uses a fixed value; TCP’s sending window uses a variable value which is determined by the header field “window-size ” of the TCP segment sent by receiver.
(3). TCP uses three-way handshake to establish a connection. Some segment’s flag bit SYN is set to 1 during the period of connection establishment.
(4). In TCP, when receiver sends a PDU with its field window-size set to 0, the sender should stop sending data; In HDLC, when receiver sends a PDU with its field type set to 2 which stands for RECEIVE-NOT-READY, the sender should stop sending data.
Chapter2 课堂练习
1. 如果在一条 3kHz 的信道上发送一个二进制信号，该信道的信噪比为 20dB，则最大可达 到的数据传输率为多少？
Answer：
A signal-to-noise ratio of 20 dB means S/N 100. Since log2101 is about 6.658, the Shannon limit is about 19.975 kbps. The Nyquist limit is 6 kbps. The bottleneck is therefore the Nyquist limit, giving a maximum channel capacity of 6 kbps.
2. 有 10 个信号，每个都要求 4000Hz，现在用 FDM 将他们复用在一条信道上。对于被复用 的信道，最小要求多少带宽？假设防护频段为 400Hz 宽。
Answer：
There are ten 4000 Hz signals. We need nine guard bands to avoid any interference.
The minimum bandwidth required is 4000 × 10 + 400 ×9 = 43,600 Hz.
3. When we use a modem, which use 16 phases signal to modulation, then how much can we get the maximum data rate in a 2400 baud channel (in noiseless channel)?
A. 400bps B. 2400bps C. 9.6kbps D. 14.4kbps
4. What is the remainder obtained by dividing x 7 + x 5 + 1 by the
6. To correct 2 single-bit errors, how many hamming distance do we need?
A. 3 B. 4 C. 5 D. 6
7. What is the maximum sending window size of the go-back-n protocol when use 4 bits for frame serial number?
A. 4 B. 8 C. 15 D. 16
Chapter4
Question 1-3 are based following figure:
1. Suppose all hosts and all routers are legacy station (cannot realize the VLAN frame). The E0 and E1 port of Switch 1 all be configured as VLAN 2, the E2 port is configured as VLAN 3, all other ports are not be configured as any VLAN. To let host A and host B can communicate with each other, what address should host B be?
A. 10.0.0.2/16 B. 11.0.0.2/8 C. 10.1.0.2/16 D. 10.1.0.2/8
2. Continuous with the configuration of question above, suppose that each Fa0 port of two switch is VLAN-aware port (can realize the VLAN frame), the E0 port of switch 2 is configured as VLAN 2, the E1 and E2 port of switch 2 all be configured as VLAN 3, the Fa1 port of switch 1 is configured as VLAN 3, the Fa1 port of switch 2 is configured as VLAN 2, all other configuration are not changed, what is the correct result?
A. host A can ping host D B. host E can ping host B
3. Continuous with the configuration of question above, if the direct connection of router 1 and router 2 is established (not show in the figure) and router 1 can ping router 2, to let host F can ping host B, what address should host F be?
A. 10.0.0.4/16 with gateway 10.0.0.200 B. 10.0.0.4/16 with gateway 10.1.0.200 C. 10.1.0.4/16 with gateway 10.1.0.200 D. 10.1.0.4/16 with gateway 10.0.0.200
4. 某局域网采用 CSMA/CD 协议实现介质访问控制，数据传输速率为 10Mbps，主 机甲和主机乙之间的距离为 2km，信号传播速度是 200000km/s。请回答下列问题，
要求说明理由或写出计算过程。
（1）若主机甲和主机乙发送数据时发生冲突，则从开始发送数据时刻起，到两 台主机均检测到冲突时刻止，最短需经过多长时间？最长需经过多长时间？ （假 设主机甲和主机乙发送数据过程中，其他主机不发送数据）
（2）若网络不存在任何冲突与差错，主机甲总是以标准的最长以太数据帧（1518 字节）向主机乙发送数据，主机乙每成功收到一个数据帧后立即向主机甲发送一 个 64 字节的确认帧，主机甲收到确认帧后方可发送下一个数据帧。此时主机甲 的有效数据传输速率是多少？（不考虑以太网帧的前导码）