Network time protocols and the Timeserv.exe utility file (266209)

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The Microsoft Windows NT Server 4.0 Resource Kit includes the utility Timeserv.exe file that allows for the synchronization of the Windows NT server with any of the public time servers. Many different time servers are available and the port through which that connection is made is based upon which RFCs that individual time server is compliant with.

Note: RFC is an acronym for Request for Comments. It refers to a document in which a standard, a protocol, or other information pertaining to the operation of the Internet is published.

If you want to change the port number to which the Timeserv.exe file connects, use Microsoft NotePad or any other standard text editor to edit the Timeserv.ini file, located in the same directory as the Timeserv.exe file. You must modify the line "type=x" (without the quotes) where "x" is either NTP or Internet as described in this article.

If the Timeserv.exe file is set to Type=NTP, it accesses port 123 of the specified server, but the outgoing port from Windows NT is dynamic. If the specified server fails, the Timeserv.exe file might try port 37, but only to present a detailed error message. If the Timeserv.exe file is set to Type=Internet, it accesses port 13 of a National Institute of Standards and Technology (NIST) server located in Boulder, Colorado.

Some of the more widely used RFCs are provided below, along with a brief description:

Daytime Protocol (RFC 867)

This protocol is widely used by small computers that run MS-DOS and similar operating systems. The server listens on port 13, and responds to requests in either Transmission Control Protocol/Internet Protocol (TCP/IP) or User Datagram Protocol/Internet Protocol (UDP/IP) formats. The standard does not specify an exact format for the Daytime Protocol, but requires that the time is sent using standard ASCII characters.

Time Protocol (RFC 868)

This simple protocol returns a 32-bit unformatted binary number that represents the time in Universal Time Coordinate (UTC) seconds since January 1, 1900. The server listens for Time Protocol requests on port 37, and responds in either TCP/IP or UDP/IP formats.

Network Time Protocol (RFC 1305)

The Network Time Protocol (NTP) is the most complex and sophisticated of the time protocols, and it is the one that provides the best performance. NTP is typically used by large computers and workstations, because NTP software is often bundled with the operating system. The client software runs continuously as a background task that periodically obtains updates from the server. The client software can be configured to query several servers, and to average the results. Since it can query multiple servers, it can ignore responses from servers that appear to send the wrong time. The NTP servers listen for a NTP request on port 123, and respond by sending a UDP/IP data packet in the NTP format.

Simple Network Time Protocol (SNTP) Version 4 (RFC 2030)

SNTP can be used when the ultimate performance of the full NTP implementation described in RFC 1305 is not needed or justified. The only significant protocol change in SNTP version 4 from previous versions of NTP and SNTP is a modified header interpretation to accommodate Internet Protocol version 6 (IPv6).