On looking at RFCs

For a useful exercise in putting network theory into practice, we can write an RFC-868 ‘client’

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’

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

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

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’

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)