Consider the networks shown in the figure. There are two user machines m1.a.com and m2.a.com in the network a.com. Suppose the user at m1.a.com types in the URL www.b.com/bigfile.htm into a browser to retrieve a 1Gbit (1000 Mbit) file from www.b.com. Internet m1.a.com Authoritative DNS server www.b.com for b.com R2 1 Gbps LAN 1 Mbps (in each direction) R1 1 Gbps LAN HTTP Local m2.a.com cache DNS server a) [6 marks] List the sequence of DNS and HTTP messages sent/received from/by m1.a.com as well as any other messages that leave/enter the a.com network that are not directly sent/received by m1.a.com from the point that the URL is entered into the browser until the file is completely received. Indicate the source and destination of each message. You can assume that every HTTP request by m1.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.