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On looking at RFCs

This exercise involves creating a client program for RFC 868, a historic protocol from the IETF that provides accurate time and date from any location on Earth. Despite being adopted over 25 years ago, RFC 868 remains in use today. Participants will read RFC 868 and write a socket program that retrieves Coordinated Universal Time (UTC) from a U.S. Naval Observatory server, then computes the current time in California (Pacific Daylight Time). An advanced task includes enhancing the program to also display the current date, incorporating leap year rules for accuracy.

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On looking at RFCs

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  1. On looking at RFCs For a useful exercise in putting network theory into practice, we can write an RFC-868 ‘client’

  2. How does a ‘protocols’ arise? • Since the inception of networking, it’s been a practice of the Internet Engineering Task Force (IETF) to circulate draft-documents known as RFCs (“Request For Comment”) which set forth detailed proposals for new network protocol standards, and then after a period for discussion and revisions to adopt these as official IETF ‘standards’

  3. RFC868 – Time Protocol • One of the early (and brief) examples of an RFC is this two-page description of a client-and-server application that provides an accurate time-and-date to computers anywhere on the Internet • It was adopted a quarter-century ago, but is still in use -- although newer protocols now offer several superior capabilities

  4. UTC • The ‘Time Protocol’ expresses the current time, at a specific location on the Earth’s surface, in terms of the number of seconds that have elapsed since January 1st, 1900 • This measurement is called Coordinated Universal Time, formerly known as GMT (Greenwich Mean Time), but allows both the time and the date to be calculated for locations in any ‘time-zone’ on the Earth

  5. In-class exercise #1 • Read RFC868 and write a ‘client’ sockets program which obtains the UTC integer from an official U.S. Naval Observatory server, then computes and displays the current time-of-day here in California now (i.e., Pacific Daylight Time), given that it’s seven hours later in Greenwich, England • Server’s hostname: ‘time-nw.nist.gov’

  6. In-class exercise #2 • Enhance your solution by also displaying the current date in California now (PDT) • This enhancement is more challenging, as you’ll need to use information about which years are ‘leap’ years – and the rules are slightly more complicated than those you may have learned in grammar school! • (See Robert Wolf’s email on our website)

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