3. Consider the networks shown in the figure below. There are two user machines ml.a.com and m2.a.com in the network a.com. Suppose the user at ml.a.com types in the URL www.b.com/bigfile.html into a browser to retrieve a 1Gbit (1000 Mbit) file from www.b.com. List the sequence of DNS and HTTP message sent/received by from ml.a.com from the point the URL is entered into the browser until the file is completely received. Indicate the sequence of messages as well as the source and destination of each message. You can assume that every HTTP request by ml.a.com is first directed to the HTTP cache in a.com and that the cache is initially empty, and that all DNS requests are iterated queries. www.b.com Authoritative DNS 1841 R2 1841 PC PC m2.a.com m1.a.com Server Server HTTP cache Local DNS Figure 1: problem 3 3. Consider the networks shown in the figure below. There are two user machines ml.a.com and m2.a.com in the network a.com. Suppose the user at ml.a.com types in the URL www.b.com/bigfile.html into a browser to retrieve a 1Gbit (1000 Mbit) file from www.b.com. List the sequence of DNS and HTTP message sent/received by from ml.a.com from the point the URL is entered into the browser until the file is completely received. Indicate the sequence of messages as well as the source and destination of each message. You can assume that every HTTP request by ml.a.com is first directed to the HTTP cache in a.com and that the cache is initially empty, and that all DNS requests are iterated queries. www.b.com Authoritative DNS 1841 R2 1841 PC PC m2.a.com m1.a.com Server Server HTTP cache Local DNS Figure 1: problem 3