On looking at RFCs

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, its 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 Earths 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 its seven hours later in Greenwich,
  England
• Servers 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 youll
  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 Wolfs email on our website)