Protocol standard - RFC

The protocol has been around for 25 years (since the early days of the Internet). It's been tweaked a few times and variations have been introduced.

• 0958 Network Time Protocol (NTP). D.L. Mills. September 1985.
• 1059 Network Time Protocol (version 1) specification and implementation July 1988
• 1119 Network Time Protocol (version 2) specification and implementation (PS only)
• 1305 Network Time Protocol (Version 3) Specification, Implementation and Analysis March 1992

• 1128 Measured performance of the Network Time Protocol in the Internet System (PS only)
• 1129 Internet Time Synchronization: The Network Time Protocol. (PS and PDF)
• 1165 Network Time Protocol (NTP) over the OSI Remote Operations Service June 1998

• 1361 Simple Network Time Protocol (SNTP). D. Mills. August 1992.
• 1769 Simple Network Time Protocol (SNTP). D. Mills. March 1995.
• 2030 Simple Network Time Protocol (SNTP) Version 4 for IPv4, IPv6 and OSI Oct 1996
• 4330 Simple Network Time Protocol (SNTP) Version 4 for IPv4, IPv6 and OSI Jan 2006

• 4075 Simple Network Time Protocol (SNTP) Configuration Option for DHCPv6 May 2005