Consider the network shown at right. Assuming: 1) that all HTTP queries originat
ID: 3888046 • Letter: C
Question
Consider the network shown at right. Assuming: 1) that all HTTP queries originating in a.com are first directed to a. com's HTTP cache, 2) that both a. com's HTTP and all DNS server caches are initially empty, and 3) that DNS queries are iterative, answer the following questions. (a) A user at m1.a.com types the URL www.b.com/bigfile.html into a browser to retrieve a big file from www.b.com. List, in order, and in the form {DNS/HTTP} {request/response} from W to X {DNS/HTTP} {request/response} from Y to Z etc all DNS and HTTP messages generated by this browser request. (b) Immediately after the big file is delivered to m1.a.com, a user at m2.a.com requests the exact same file from ww.b.com. List, in order, in the same form as displayed above, all DNS and HTTP messages generate by this request. (c) Would your answer to (a) change if the all DNS queries were recursive? If so, rework (a) in this case. How about (b)? If so, rework (b) in this case. (d) It is often said that iterative DNS queries are "less burdensome" to DNS servers than recursive DNS queries. Why?Explanation / Answer
Answer:
(A) When the user types this URL: www.b.com/bigfile.html in the browser.
Request message of HTTP is quite simple and for the m1.a.com user
(B) Request message of HTTP is quite simple and for the m2.a.com user
(C) No, DNS message generated by the browser request will be same in both the cases because DNS is server and server only send and accept the request from the browser with a specific IP. so if the searching result changes from the browser it won't affect the DNS.
(D) Yes, iterative DNS queries are easy to manage and faster to respond than the recursive DNS queries. Because when you search for a query in your web browser then it sends a request to DNS and then DNS find that request and show you the result in your browser. If the queries are some what similar then it takes less time for the DNS to find the things because some of the information is stored in your system which is said to be cache, which browser automatically detect and take and other information will be taken by the DNS according to your queries.
So, that is why iterative DNS queries are less burdensome than the recursive DNS queries.
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