Homework Chapter 2

一。什么是数据库?

b。使用各种whois数据库在互联网上获得两个DNS服务器的名称。显示您使用whois数据库。(例如,www.mit.edu,www.mit.edu,www.yahoo.com,www.bupt.edu.cn)

c。在本地主机上使用网路资讯查询发送DNS查询三个DNS服务器:本地DNS服务器和两个DNS服务器(b)部分中你发现。试着查询类型,NS,MX报告。总结你的发现。

d。使用nslookup找到Web服务器有多个IP地址。BUPT的Web服务器有多个IP地址?

e。使用后面瞎跑whois数据库,以确定你所使用的IP地址范围的机构(如。www.mit.edu,www.google.com,www.bupt.edu.cn)。

7. Suppose you can access the caches in the local DNS servers of your department. Can you propose a way to roughly determine the Web servers (outside your department) that are most popular among the users in your department? Can you come up a way to determine if an external Web site was very likely accessed from a computer in your department a couple of seconds ago? Explain.

假设你可以访问本地的缓存DNS服务器你的部门。你能提出一个方法大致确定Web服务器(本部门以外的)中最受欢迎的用户在你的部门吗?你能想出一个方式来确定外部网站很可能从你们部门的计算机访问几秒钟前?解释一下。

8. Consider distributing a file of F = 15 Gbits to N peers. The server has an upload rate of us = 30 Mbps, and each peer has a download rate of di = 2 Mbps and an upload rate of u. For N = 10, 100, and 1,000 and u = 300 Kbps, 700 Kbps, and 2 Mbps, prepare a chart giving the minimum distribution time for each of the combinations of N and u for both client-server distribution and P2P distribution.

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9. In our coverage of an overlay networks using query flooding, we described in some detail how a new peer joins the overlay network. In this problem we want to explore what happens when a peer leaves the overlay network. Suppose every participating peer maintains TCP connections to at least four distinct peers at all times. Suppose Peer X, which has five TCP connections to other peers, wants to leave.

a. First consider the case of a graceful departure, that is, Peer X explicitly closes its application, thereby gracefully closing its five TCP connections. What actions would each of the five formerly connected peers take?

b. Now suppose that Peer X abruptly disconnects from the Internet without notifying its five neighbors that it is closing the TCP connections. What would happen?

在我们覆盖的覆盖网络，使用查询洪水，我们在一些细节描述了如何一个新的对等连接的覆盖网络。在这个问题上，我们要探索发生什么情况时，一个对等网的覆盖网络。假设每个参与节点保持TCP连接的至少四个不同的节点都。想点X，其中有五个TCP连接到其他的同行，想离开。

首先考虑一个优雅的离去，是这样的，同行的X显式地关闭应用，从而优雅地关闭其五的TCP连接。五个以前连接的同行会采取什么行动？

现在假设同伴X突然断开与互联网没有通知其五个邻居是关闭TCP连接。会发生什么？

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a. 在这种情况下，这五个客户都立即知道它们少了一个邻居。考虑五个客户中的一个，比如A。假设当 X 离开后，A只有三个邻居。这是A需要同另一个对等点建立 TCP 连接。A要有一个活跃对等点的最新列表；他不断地连接列表中地对等点知道其中一个接收它的 TCP 连接请求。

b. 在这种情况下，Bob 不能立即知道 X 已经离开了。只有当他尝试向 X 发送信息（query 或 ping）时，Bob 才会知道 X 已经离开。当 Bob 尝试发送信息时，Bob 的 TCP 将会产生数个不成功的连接信息。这时 Bob 的 TCP 将会通知 Gnutella 客户机 X 已经离开。然后 Bob 将会尝试与一个新的对等点建立 TCP 连接，以此重建第五个连接.

10. What is an overlay network? Does it include routers? What are the edges in the overlay network? How is the query-flooding overlay network created and maintained?

什么是覆盖网络？它包括路由器吗？覆盖网络中的边是什么？查询的洪水覆盖网络的创建和维护？

11. What is the difference between Network Architecture and Application Architecture?

网络体系结构和应用架构有什么区别？

12. List five non-proprietary Internet applications and the application-layer protocols, transport-layer protocols that they use.

列出五个非专利的互联网应用程序和应用层协议，传输层协议，它们使用。

13. Suppose you wanted to do a transaction from a remote client to a server as fast as possible. Would you use UDP or TCP? Why?

假设你想尽可能快速地从远程客户端到服务器的事务处理。你会使用UDP或TCP？为什么？

14. For the client-server application over TCP, why must the server program be executed before the client program? For the clientserver application over UDP, why may the client program be executed before the server program?

对于客户端-服务器应用程序的TCP服务器程序，为什么必须在客户端程序执行？对于CS应用UDP，为什么客户端程序在服务器程序执行？

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