The Time Protocol is a network protocol in the

Internet Protocol Suite The Internet protocol suite, commonly known as TCP/IP, is a framework for organizing the set of communication protocols used in the Internet and similar computer networks according to functional criteria. The foundational protocols in the sui ...

defined in 1983 in RFC 868 by

Jon Postel Jonathan Bruce Postel (; August 6, 1943 – October 16, 1998) was an American computer scientist who made many significant contributions to the development of the Internet, particularly with respect to standards. He is known principally for bein ...

and K. Harrenstein. Its purpose is to provide a site-independent, machine readable date and time. The Time Protocol may be implemented over the

Transmission Control Protocol The Transmission Control Protocol (TCP) is one of the main protocols of the Internet protocol suite. It originated in the initial network implementation in which it complemented the Internet Protocol (IP). Therefore, the entire suite is commonl ...

(TCP) or the

User Datagram Protocol In computer networking, the User Datagram Protocol (UDP) is one of the core communication protocols of the Internet protocol suite used to send messages (transported as datagrams in packets) to other hosts on an Internet Protocol (IP) netwo ...

(UDP). A host connects to a server that supports the Time Protocol on port 37. The server then sends the time as a 32-bit unsigned integer in binary format and in

network byte order In computing, endianness, also known as byte sex, is the order or sequence of bytes of a word of digital data in computer memory. Endianness is primarily expressed as big-endian (BE) or little-endian (LE). A big-endian system stores the most s ...

, representing the number of seconds since 00:00 (midnight) 1 January, 1900 GMT, and closes the connection. Operation over UDP requires the sending of any datagram to the server port, as there is no connection setup for UDP. The fixed 32-bit data format means that the timestamp rolls over approximately every 136 years, with the first such occurrence on 7 February 2036. Programs that use the Time Protocol must be carefully designed to use context-dependent information to distinguish these dates from those in 1900. Many

Unix-like A Unix-like (sometimes referred to as UN*X or *nix) operating system is one that behaves in a manner similar to a Unix system, although not necessarily conforming to or being certified to any version of the Single UNIX Specification. A Unix-li ...

operating systems used the Time Protocol to monitor or synchronize their clocks using the rdate utility, but this function was superseded by the

Network Time Protocol The Network Time Protocol (NTP) is a networking protocol for clock synchronization between computer systems over packet-switched, variable- latency data networks. In operation since before 1985, NTP is one of the oldest Internet protocols in ...

(NTP) and the corresponding

ntpdate ntpdate is a computer program used to quickly synchronize and set computers' date and time by querying a Network Time Protocol (NTP) server. It is available for a wide variety of unix-like operating systems. The accuracy and reliability of n ...

utility. NTP is more sophisticated in various ways, among them that its resolution is finer than one second.

Inetd implementation

On most UNIX-like operating systems a Time Protocol server is built into the

inetd inetd (internet service daemon) is a super-server daemon on many Unix systems that provides Internet services. For each configured service, it listens for requests from connecting clients. Requests are served by spawning a process which runs the ...

(or

xinetd In computer networking, xinetd (''Extended Internet Service Daemon'') is an open-source super-server daemon which runs on many Unix-like systems, and manages Internet-based connectivity. It offers a more secure alternative to the older inetd ...

) daemon. The service is usually not enabled by default. It may be enabled by adding the following lines to the file {{mono, /etc/inetd.conf and reloading the configuration. time stream tcp nowait root internal time dgram udp wait root internal

External links

vervest.org - HTTP Time Protocol

Network time-related software Application layer protocols

Inetd implementation

See also

External links