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- Network Working Group J. Postel - ISI
- Request for Comments: 868 K. Harrenstien - SRI
- May 1983
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- Time Protocol
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- This RFC specifies a standard for the ARPA Internet community. Hosts on
- the ARPA Internet that choose to implement a Time Protocol are expected
- to adopt and implement this standard.
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- This protocol provides a site-independent, machine readable date and
- time. The Time service sends back to the originating source the time in
- seconds since midnight on January first 1900.
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- One motivation arises from the fact that not all systems have a
- date/time clock, and all are subject to occasional human or machine
- error. The use of time-servers makes it possible to quickly confirm or
- correct a system's idea of the time, by making a brief poll of several
- independent sites on the network.
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- This protocol may be used either above the Transmission Control Protocol
- (TCP) or above the User Datagram Protocol (UDP).
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- When used via TCP the time service works as follows:
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- S: Listen on port 37 (45 octal).
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- U: Connect to port 37.
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- S: Send the time as a 32 bit binary number.
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- U: Receive the time.
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- U: Close the connection.
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- S: Close the connection.
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- The server listens for a connection on port 37. When the connection
- is established, the server returns a 32-bit time value and closes the
- connection. If the server is unable to determine the time at its
- site, it should either refuse the connection or close it without
- sending anything.
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- Postel [Page 1]
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- RFC 868 May 1983
- Time Protocol
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- When used via UDP the time service works as follows:
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- S: Listen on port 37 (45 octal).
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- U: Send an empty datagram to port 37.
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- S: Receive the empty datagram.
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- S: Send a datagram containing the time as a 32 bit binary number.
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- U: Receive the time datagram.
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- The server listens for a datagram on port 37. When a datagram
- arrives, the server returns a datagram containing the 32-bit time
- value. If the server is unable to determine the time at its site, it
- should discard the arriving datagram and make no reply.
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- The Time
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- The time is the number of seconds since 00:00 (midnight) 1 January 1900
- GMT, such that the time 1 is 12:00:01 am on 1 January 1900 GMT; this
- base will serve until the year 2036.
-
- For example:
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- the time 2,208,988,800 corresponds to 00:00 1 Jan 1970 GMT,
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- 2,398,291,200 corresponds to 00:00 1 Jan 1976 GMT,
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- 2,524,521,600 corresponds to 00:00 1 Jan 1980 GMT,
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- 2,629,584,000 corresponds to 00:00 1 May 1983 GMT,
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- and -1,297,728,000 corresponds to 00:00 17 Nov 1858 GMT.
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- Postel [Page 2]
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