Consider the DNS name resolution processing that results from typing a cnn.com URL into a web browser. Assume the cnn page is composed of a base HTML page that contains references to three objects for so-called "banner ads" supplied by advertising agencies. The banner adds are images stored on web servers operated by the advertising agency or some third-party content distribution company. The URLs for the base page and three embedded objects (taken from a real web page) are: http://www.cnn.com (Base page.) http://a30.g.akamai.net/f/30/1162/1h/images.cnn.com/ads/advertiser/worldcom/011/cnn.worldcom.gif http://a76.h.akamai.net/f/76/1162/1h/images.cnn.com/ads/advertiser/cnn/011/234x60.career.gif http://www2.cnn.com/cookie.crumb How much time does it take to perform the DNS name resolutions required to request all four URLs? Express your answer in terms of the number of DNS query/reply round trip times (RTTs) needed. Show clearly how you derived your answer. In your analysis you may assume: - The local name server is also an authoritative name server for the local domain. - The local name server has a large cache but it is empty when processing for these URLs first begins, the URLs are processed in the order given above, and no other resolvers use the local server until all four URLs have been requested. - The DNS query/reply round-trip time between any two DNS servers is constant and the same constant for all server pairs. - The round-trip latency between the browser's resolver and the local authoritative server is negligible. - The local authoritative name server always sends iterated queries. - For the host names in the above URLs, there is always a different authoritative name server for each domain in the name hierarchy