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?
   是否有申请日程序？

5. Creating a UDP client by Pytion. clientSocket = socket(socke: AF_INET, socket.
   通过 Pytion 创建 UDP 客户端：AF_INET, socket.
   A. SOCK DGRAM
6. SOCK RAW
   C. SOCK STREAN.
   D. SOCK PACKET
7. In RDT model
   A. rdit sendi)
   B. rd: revi()
   C. udt deliver()
   D. ud! rev()

7. In RDT1.0 model

8. 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

9. 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
   B.
   C.
   D.
10. 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
11. Which of the following is false with respect to UDP
    关于 UDP，以下哪项是错误的

12. 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
13. 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

14. 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

15. 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（ ）？

16. Which is not one of the routing protocol (
    哪个不是路由协议 (
    A. OSPF B.RIP
    C. BGP
    D. ICMP
17. Which protocol is no collision ()
    哪种协议没有碰撞 ()
18. 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
19. 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
20. 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 和
2. is a protocol used to provide quick, automatic, and central management for the
   是一种协议，用于快速、自动和集中地管理

3. 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.
   计算或网络是一种分布式应用程序架构，它将任务或工作负载划分给对等方。对等方是应用程序中具有同等权限的平等参与者。
4. and "Selective Repeat Protocol" are the sliding window protocols.
   和 "选择性重复协议 "是滑动窗口协议。
5. 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： 和 (2)
6. 
   is used by hosts and routers to communicate network layer information to each other. The most typical use of it is for error reporting
   被主机和路由器用来相互传递网络层信息。最典型的用途是错误报告

9. is a multi port bridge with a buffer and a design that can boost its efficiency, a
   是一种带有缓冲器的多端口桥接器，其设计可以提高效率，是一种

11. There are two fundamental approaches to moving data through a network of links and switches: circuit switching and
    通过链路和交换机网络传输数据有两种基本方法：电路交换和
12. is a transport-layer protocols which provides an unreliable, connectionless service to the invoking application.
    是一种传输层协议，为调用应用程序提供不可靠的无连接服务。
13. The most important of delays in network are the nodal processing delay, queuing delay, and
    网络中最重要的延迟包括节点处理延迟、排队延迟、 和

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?
   互联网协议栈有哪五层？每一层的主要职责是什么？
2. List five nonproprictary application-layer protocols, the underlying transport-layer protocols and ports.
   列出五个非限制性应用层协议、底层传输层协议和端口。

3. 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。
4. List the three categories of multiple access protocols, and describe at least two typical techniques introduced in each type
   列出三类多路访问协议，并描述每类协议中引入的至少两种典型技术
5. 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）

2. 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