Network Time Protocol (NTP)
Description
NTP version 4 is compliant to RFC 2030 (Simple Network Time Protocol). It is available from AIX 6.1.
The Network Time Protocol (NTP) is widely used to synchronize a computer to Internet time servers or other sources, such as a radio or satellite receiver or telephone modem service. It provides accuracies typically less than a millisecond on LANs and up to a few milliseconds on WANs. Typical NTP configurations use multiple redundant servers and diverse network paths to achieve high accuracy and reliability.
NTP time synchronization services are widely available in the public internet. The public NTP subnet in early 2008 includes several thousand servers in most countries and on every continent of the globe, including Antarctica. These servers support a total population that is estimated at over 25 million computers in the global internet.
The NTP subnet operates with a hierarchy of levels, where each level is assigned a number that is called the stratum. Stratum 1 (primary) servers at the lowest level are directly synchronized to national time services. Stratum 2 (secondary) servers at the next higher level are synchronized to stratum 1 servers, and so on. Normally, NTP clients and servers with a relatively small number of clients do not synchronize to public primary servers. Several hundred public secondary servers operate at higher strata and are the preferred choice.
AIX Version 7.2, and earlier, supports both NTP version 3 and NTP version 4. Both NTP versions are supported by using symbolic links from the /usr/sbin directory to the NTP binary files of one of the NTP versions. Starting with AIX Version 7.3, NTP version 3 is removed. For compatibility with earlier versions of NTP, the symbolic links point to NTP version 4 binary files by default so that the same commands continue to work.
NTP version 4 binary file | Default symbolic links to NTP version 4 binary files |
---|---|
ntpd4 | /usr/sbin/xntpd-->/usr/sbin/ntp4/ntpd4 |
ntpdate4 | /usr/sbin/ntpdate-->/usr/sbin/ntp4/ntpdate4 |
ntpdc4 | /usr/sbin/xntpdc-->/usr/sbin/ntp4/ntpdc4 |
ntpq4 | /usr/sbin/ntpq-->/usr/sbin/ntp4/ntpq4 |
ntp-keygen4 | /usr/sbin/ntp-keygen-->/usr/sbin/ntp4/ntp-keygen4 |
ntptrace4 | /usr/sbin/ntptrace-->/usr/sbin/ntp4/ntptrace4 |
sntp4 | /usr/sbin/sntp-->/usr/sbin/ntp4/sntp4 |