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Part One. Multiple choice (蕇选片), one point per question, total of points
第一部分。多项选择题(蕇选片),每题 1 分,共
  1. The IETF star:dards documents are called
    IETF 星:标准文件称为

    A. R:C
    C ID None of the mentioned
  2. Suppose users share a 2 Mibps Zink. Aiso suppose each use: transmits comtinuously at i Nobps when transmitting, but eaci user transmits only 20 percent of the time. When circuit switching is usec, how many users can be supported ?
    假设用户共享一个 2 Mibps 的 Zink。又假设每个用户:在传输时以 i Nobps 持续传输,但其中一个用户仅在 20% 的时间内传输。当使用电路交换时, ,可以支持多少个用户?

    A. : B. 2
    C. 3
  3. Suppose jlos: wants to send a lasge file to Hos: B. The path from Host to Hos: has three links, of zates kops, Mipps, and Mips. Suppose the file is 4 million by:es. Dividing the file size by the throughput, roughly how ,ong will it take to transfer the file to Host B ? A. 6 is B. 325 C. 165 D. 85
    假设 jlos: 希望向 Hos 发送一个 lasge 文件:从主机 到 Hos: 的路径有三个链接,分别是 kops、 Mipps 和 Mips。假设文件为 400 万字节。将文件大小除以吞吐量,将文件传输到主机 B 大概需要多少时间?A. 6 is B. 325 C. 165 D. 85
  4. Wiach ts an application dayer protoco?
  1. Creating a UDP client by Pytion. clientSocket = socket(socke: AF_INET, socket.
    通过 Pytion 创建 UDP 客户端:AF_INET, socket.

  3. In RDT model
    A. rdit sendi)
    B. rd: revi()
    C. udt deliver()
    D. ud! rev()
  1. In RDT1.0 model
rdt1.0: sending side
A. ict_senc(cata)
3. Lded send(packet)
C. rdt revtpaciee:
  1. The following fgure deseribes which protocol runs instance ( )?
    下面的图说明哪个协议运行实例( )?

A. Siop-and-wai
B. Selective-repea
C. Go-Back-N
D. All of the above protocols are possible
D. 以上所有协议均可使用
  1. If the linh handwidth is , the maxumum length of the datagram is 1 , the working window is a masumum of datagrams, and the round-trip delay is , then the best efficiency of the GBN protocol is ( )?
    如果线手宽为 ,数据报的最大长度为 1,工作窗口为 数据报的总和,往返延迟为 ,则 GBN 协议的最佳效率为( )?

    A. N(L.R)/RTT
  2. Suppose 1 lost sends two TCP segments back to Host over a TCP comection. The first segment has sequence number 90 ; the second has sequence number 110 . How much data is in the first segment () ?
    假设 1 个丢失的 通过 TCP 连接向主机 发送了两个 TCP 网段。第一个数据段的序列号为 90;第二个数据段的序列号为 110。第一个数据段有多少数据( )?

    A. 90 B. C. D. 21
  3. Which of the following is false with respect to UDP
    关于 UDP,以下哪项是错误的
A. Connection-oriented B. Unreliable
A.面向连接 B. 不可靠
C. Transport layer protocol D. All of the mentioned
C.传输层协议 D. 上述所有
  1. If the subnet mask is 255.255 .224 .0 , which of the following IP addresses is not in the same network as other addresses ( )?
    如果子网掩码为 255.255 .224 .0 ,下列哪个 IP 地址与其他地址不在同一网络中( )?

    A. 172.25 .15 .200
    B. 172.25 .25 .15
    C. 172.25 .5 .200
    D. 172.25 .35 .15
  2. 255255.255 .224 may represent ()
    255255.255 .224 可表示 ()

    A. A Class C network address
    B. A broadcast address in a Class C network
    B. C 类网络中的广播地址
C. A standard network mask for a Class C nctwork
C.C 类网络的标准网络掩码
D. There are addresses that can be assigned to the host in this subnet
D.有 地址可分配给该子网中的主机
  1. The computation of the shortest path in OSPF is usually donc by ()
    OSPF 中最短路径的计算方法通常是( )。

    A. Bellman-ford algorithm
    B. Routing information protoco
    B. 路由信息原型

    D. Distance vector routing
C. Dijkstra's algorithm
  1. Which of the following is not a characteristic of Virual Circuit Network ( )?
    以下哪项不是虚拟电路网络的特征( )?
A. There are setup and teardown phases in addition to the data transfer phase
B. Resources can be allocated during setup phase or on demand
C. All packets follow the same path established during the connection
D. Virtual circuit network is implemented in application laye
  1. Which is not one of the routing protocol (
    哪个不是路由协议 (

    C. BGP
    D. ICMP
  2. Which protocol is no collision ()
    哪种协议没有碰撞 ()
  3. Fithernct frame consists of
    Fithernct 框架包括

    A. MAC address
    B. IP address
    C. both (a) and (b)
    D. none of the mentioned
  4. Which of the following field in IPv4 datagram is not related to fragmentation? A. Flags B.Ofset C.TOS D. Identifier
    IPv4 数据报中的以下哪个字段与分片无关?A. 标志 B.Ofset C.TOS D. 标识符
  5. which is not the basic elements of a ? ()
    哪个不是 的基本要素?()

    A. the L.AN topology
    B. the transmission media
    C. Media access control method
    C. 媒体访问控制方法

    D. Network operating system

Part Two. Fill-in-the-blank (填空兌), each point per blank, total of 15 points
第二部分。填空兌,每空一分,共 15 分

  1. the most commonly used Email protocols on the internet - POP and
    互联网上最常用的电子邮件协议 - POP
  2. is a protocol used to provide quick, automatic, and central management for the
distribution of IP addresses within a network. It is also used to configure the proper subnet mask, default gateway, and DNS server information on the device.
在网络中分配 IP 地址。它还用于在设备上配置适当的子网掩码、默认网关和 DNS 服务器信息。
  1. is a directory service that translates hostnames to IP addresses. computing or networking is a distributed application architecture that partitions tasks or workloads between peers. Peers are equally privileged, equipotent participants in the application.
  2. and "Selective Repeat Protocol" are the sliding window protocols.
    和 "选择性重复协议 "是滑动窗口协议。
  3. Historically, two routing protocols have been used extensively for routing within an autonomous system in the Internet: the and (2)
    互联网自治系统内的路由选择历来广泛使用两种路由选择协议: (2)

  4. is used by hosts and routers to communicate network layer information to each other. The most typical use of it is for error reporting
8 is a networking device that forwards data packets between computer networks.
8 是在计算机网络之间转发数据包的网络设备。
  1. is a multi port bridge with a buffer and a design that can boost its efficiency, a
data link layer device that perform error checking and forwarding data.
10 . is a nctwork protocol that listens to or senses network signals on the carrier/medium before transmitting any data.
10. 是一种网络协议,在传输任何数据之前会监听或感知载波/介质上的网络信号。
  1. There are two fundamental approaches to moving data through a network of links and switches: circuit switching and
  2. is a transport-layer protocols which provides an unreliable, connectionless service to the invoking application.
  3. The most important of delays in network are the nodal processing delay, queuing delay, and

Part Three. Answer the following questions briefly(简答䖯), 7 points per question, total of 35 points
第三部分。简要回答下列问题(简答䖯),每题 7 分,共 35 分

  1. What are the five layers in the Internet protocol stack? What are the principal responsibilities of each of these layers?
  2. List five nonproprictary application-layer protocols, the underlying transport-layer protocols and ports.

  1. Describe how ARP protocol works to help a host to successfully send a datagram to its destination once has no idea about 's MAC address.
    说明当 不知道 的 MAC 地址时,ARP 协议如何帮助主机 成功地向目的地 发送数据报。
  2. List the three categories of multiple access protocols, and describe at least two typical techniques introduced in each type
  3. Describe the four-step process about how DHCP protocol works.
    描述有关 DHCP 协议如何工作的四步流程。

Part Four. Analysis and computing(分析计算題), total of 30 points

  1. Consider the following network. With the indicated link costs, use Dijkstra's shortest-path algorithm to compute the shortest path from to all network nodes. Show how the algorithm works by filling the following table. (total of 10 points, 0.5 points per cell)
    考虑以下网络。使用 Dijkstra 最短路径算法计算从 到所有网络节点的最短路径。请填写下表,说明该算法是如何运行的。(共 10 分,每格 0.5 分)
  1. Assuming TCP Reno is the protocol experiencing the behavior shown in the Figure below, answer the following questions. In all cases, you should provide a short discussion justifying your answer
    假设 TCP Reno 是出现下图所示行为的协议,请回答下列问题。在所有情况下,您都应提供简短的讨论,说明答案的理由
a. Identify the intervals of time when TCP slow start is operating. (1 point)
a.确定 TCP 慢启动运行的时间间隔。(1 分)
b. Identify the intervals of time when TCP congestion avoidance is operating (1 point)
b.确定 TCP 拥塞避免运行的时间间隔(1 分)
c. After the 16 th transmission round, is segment loss detected by a triple duplicate ACK or by a timeout? (1 point)
c.在第 16 轮传输后,是通过三重重复 ACK 还是超时检测到网段丢失? (1 分)
d. After the 22 nd transmission round, is segment loss detected by a triple duplicate or by a timeout? (1 point)
d.在第 22 轮传输后,是通过三重重复 还是超时来检测段丢失?(1 分)
e. What is the initial value of ssthresh at the first transmission round? (1 point)
e.第一轮传输时 ssthresh 的初始值是多少?(1 分)
f. What is the value of ssthresh at the 18th transmission round? (1 point)
f.第 18 轮传输时 ssthresh 的值是多少?(1 分)
g. What is the value of ssthresh at the 24 th transmission round? (1 point)
g.第 24 轮传输时的 ssthresh 值是多少?(1 分)
h. During what transmission round is the 70 th segment sent? (3 points)
h.第 70 个数据段是在哪一轮传输中发送的?(3 分)
Consider a datagram network using 32 -bit host addresses. Suppose a router has four links, numbered 0 through 3, and packets are to be forwarded to the link interfaces as follows:
考虑一个使用 32 位主机地址的数据报网络。假设路由器有四个链路,编号为 0 至 3,数据包按如下方式转发到链路接口:
Destination Address Range Link Interface
Otherwise 3
a. Provide a forwarding table that has five entries, uses longest prefix matching, and forwards packets to the correct link interfaces. (4 points)
a.提供一个有五个条目的转发表,使用最长前缀匹配,并将数据包转发到正确的链路接口。(4 分)
b. Describe how your forwarding table determines the appropriate link interface for datagrams with destination addresses: ( 6 points)
b.说明转发表如何为目标地址的数据报确定适当的链路接口: ( 6 分)