Q U E S T I O N 3 In the current version of IP (IPv4), the use of TCP and UDP headers differ in which of the following ways?

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1 Preview Test: HW 2 Test Information Description Chapter 2 Instructions Due:Oct PM Multiple Attempts Not allowed. This test can only be taken once. Force Completion This test can be saved and resumed later. Question Completion Status: Save and Submit Q U E S T I O N 1 Suppose a client sends an HTTP request message with the If-modified-since: header. Suppose the object in a server has not changed since the last time a client retrieved the object. Then the server will send a response message with the status code: 304 Not Modified 200 OK 404 Not Found none of the above Q U E S T I O N 2 A server can use cookies to determine a user's postal address without the user's consent. True False Q U E S T I O N 3 In the current version of IP (IPv4), the use of TCP and UDP headers differ in which of the following ways? TCP checksums are optional but UDP checksums are mandatory UDP checksums are optional but TCP checksums are mandatory TCP checksums are larger than UDP checksums UDP checksums are larger than TCP checksums Q U E S T I O N 4 Local DNS name servers never cache resource records obtain resource records from Web caches cache resource records and never discard them cache resource records, but discard them after a period of time that is on the order of a few days

2 7 points Q U E S T I O N 5 Suppose the HTML file references 12 very small objects on the same web server. Neglecting transmission times, how much time elapses in total (in terms of RTTs) with Non-persistent HTTP with no parallel TCP connections? Provide your answer only in number - Do not include any other strings such as "RTT" in your answer. 7 points Q U E S T I O N 6 Suppose the HTML file references 12 very small objects on the same web server. Neglecting transmission times, how much time elapses in total (in terms of RTTs) with Persistent HTTP without parallel TCP connections? Provide your answer only in number - Do not include any other strings such as "RTT" in your answer. Q U E S T I O N 7 With SMTP, it is possible to send multiple mail messages over the same TCP connection. True False Q U E S T I O N 8 Which of the following higher-level protocols typically operate on top of UDP? 3 points DNS Telnet TCP All of the above Q U E S T I O N 9 Suppose a DNS resource record has Type=MX. Then Value is the hostname of the DNS server that is authoritative for Name. Value is the IP address of the mail server that has the alias hostname Name. Value is the hostname of the mail server that has the alias hostname Name. none of the above Q U E S T I O N 1 0 What is traceroute used for? Explain how it works. Q U E S T I O N 1 1 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 hand-shaking)

3 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. Q U E S T I O N 1 2 Consider the minimum time for P2P file distribution. Suppose the upload rate of the server is10 Mbps, the upload rates of all peers is 1 Mbps, and the download rates of all peers is 10 Mbps. Further suppose that there are 100 peers and the file is 100 million bits. The minimum distribution time is approximately 100 seconds approximately 1000 seconds approximately 10 seconds approximately 1 second Q U E S T I O N 1 3 Sketch the paired flowcharts for a streams (TCP) server and client showing the key sockets function calls (you need not give the arguments to each sockets function call, just identify it by name such as connect(), socket(), and so on) Q U E S T I O N 1 4 A browser will generate header lines as a function of browser type and version user configuration of browser whether the browser has a cached version of the requested object all of the above Q U E S T I O N 1 5 Consider the following network which consists of two end hosts and one router. 10 points A_ Router B The link between host A and the router has the following characteristics: The link between host A and the router has the following characteristics: Link bandwidth = 5 Mbps Distance = 1000 meters Signal propagation velocity = meter/sec Packet size = bits

4 The link between the router and host B has the following characteristics (Assume that there are no processing and queue delays): Link bandwidth = 10 Mbps Distance = 2000 meters Signal propagation velocity = meter/sec Packet size = bits Find out the total delay to send two packets of the same size (10000 bits) from A to B. Q U E S T I O N 16 The so-called "registered" TCP and UDP port numbers fall into which numeric range? 1024 to to to to Q U E S T I O N 1 7 W h a t i s t h e s i z e o f a T C P h e a d er? 4 points Q U E S T I O N 1 8 Suppose within your Web browser you click on a link to obtain a Web page. 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 RTT 1,..., RTT_n. Further suppose that the Web page associated with the link contains exactly one object, consisting of a small amount of HTML text. Let RTT_0 denote the RTT between the local host and the server containing the object. Assuming zero transmission time of the object. Suppose the HTML file references eight very small objects on the same server. Neglecting transmission times, a. how much time elapses with a. Non- persistent HTTP with no parallel TCP connections? b. Non- persistent HTTP with the browser configured for 5 parallel connections? c. Persistent HTTP?

5 root DNS server 2 3 TLD DNS server 4 5 local DNS server dns.poly.edu requesting host cis.poly.edu authoritative DNS server dns.cs.umass.edu Q U E S T I O N 1 9 An application layer protocol typically defines four things. What are these four things?