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简答题 Suppose that in UDPClient.py, after we create the socket, we add the line: clientSocket.bind(('', 5432)) Will it become necessary to change UDPServer.py? What are the port numbers for the sockets in UDPClient and UDPServer? What were they before making this change
学科：网络与通信原理
时间：2023-06-21 12:41:09
题目1简答题
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题目2简答题
1.Suppose the IP address for the associated URL is not cached in your local host, so a DNS lookup is necessary to obtain the IP address. Suppose that n DNS servers are visited before your host receives the IP address from DNS; the successive visits incur an RTT of RTT1, . . . , RTTn. Further suppose that the Web page associated with the link contains exactly one object, consisting of a small amount of HTML text. Let RTT0 denote the RTT between the local host and the server containing the object. Assuming zero transmission time of the object, how much time elapses from when the client clicks on the link until the client receives the object? 2. Suppose the HTML file references eight very small objects on the same server. Neglecting transmission times, how much time elapses with a. Non-persistent HTTP with no parallel TCP connections? b. Non-persistent HTTP with the browser configured for 6 parallel connections? c. Persistent HTTP题目3简答题
1. Estimate how many time your unlock your mobile phone screen, and how long do you use your phone? Don't rush, take at least 1 minute to calculate, and then make your guess. 2. Take your mobile phone, open the SETTING-->Screen Time Management (there could be different names for this function) function, and check the total time you spent on the screen in the past 7 days,. Take a snapshot of the statistics of the time you spent on the screen last week, the AVERAGE number of times you unlocked your screen each day. How is it different from your estimation? 3. Referring to the previous question. When you use your phone, if DNS looking up happens once every 10 minutes, and each time the HTTP file references 8 objects, how much time elapses with Non-persistent HTTP, and no parallel TCP connections题目4简答题
Consider a short, 10-meter link, over which a sender can transmit at a rate of 150 bits/sec in both directions. Suppose that packets containing data are 100,000 bits long, and packets containing only control (e.g., ACK or handshaking) are 200 bits long. Assume that N parallel connections each get 1/N of the link bandwidth. Now consider the HTTP protocol, and suppose that each downloaded object is 100 Kbits long and that the initial downloaded object contains 10 referenced objects from the same sender. Would parallel downloads via parallel instances of non-persistent HTTP make sense in this case? Now consider persistent HTTP. Do you expect significant gains over the non-persistent case? Justify and explain your answer题目5简答题
Write a simple TCP program for a server that accepts lines of input from a client and prints the lines onto the server's standard output. (You can do this by modifying the TCPServer.py program in the text.) Compile and execute your program. On any other machine that contains a Web browser, set the proxy server in the browser to the host that is running your server program; also configure the port number appropriately. Your browser should now send its GET request messages to your server, and your server should display the messages on its standard output. Use this platform to determine whether your browser generates conditional GET messages for objects that are locally cached题目6简答题
Consider distributing a file of F bits to N peers using a client-server architecture. Assume a fluid model where the server can simultaneously transmit to multiple peers, transmitting to each peer at different rates, as long as the combined rate does not exceed Us. a. Suppose that Us/N≤dmin. Specify a distribution scheme that has a distribution time of NF/us. b. Suppose that Us/N≥dmin. Specify a distribution scheme that has a distribution time of F/dmin. c. Conclude that the minimum distribution time is in general given by max{NF/Us, F/dmin}题目7简答题
Suppose that in UDPClient.py, after we create the socket, we add the line: clientSocket.bind(('', 5432)) Will it become necessary to change UDPServer.py? What are the port numbers for the sockets in UDPClient and UDPServer? What were they before making this change