![]() ![]() key ID & MAC: Only present when you’re using NTP authentication.If you roughly want to know the time by looking at an NTP packet, look at this transmit timestamp. transmit timestamp: “Time at the server when the response left for the client.” This is the most interesting timestamp in those NTP packets since it shows the time the NTP client/server had as it sent the NTP packet.( Since I am merely using IPv6 for this NTP blog post series you’ll always see these curious-looking “refid” values in the ntpq output. Above stratum 1 this is either the IPv4 address of the reference NTP server or for IPv6 “it is the first four octets of the MD5 hash of the IPv6 address.” <- D’oh! This looks quite strange. reference ID: “32-bit code identifying the particular server or reference clock.” For stratum 1 servers this is an ASCII string telling you the reference clock such as GPS, PPS or DCFa/DCFp.Supported are values up to 15, while 16 means unsynchronized. ) You won’t see values greater than 4 on the Internet that often. An NTP server that receives its time from a stratum 1 server increases the value by 1, that is: 2. ![]() That is: When a server replies with stratum 1, it is directly connected to a reference clock. While the reference clock (if one is used) internally has a stratum value of 0, the NTP server that syncs to that clock has a stratum value of 1. stratum: The stratum value gives the distance to the reference clock.Other modes are “symmetric active” (2) between NTP peers and “NTP control message” (6) for controlling/polling NTP servers. This is the basic client-server unicast request which you’ll see all over your network. mode: The most common modes are client (3) and server (4).version: “3-bit integer representing the NTP version number, currently 4.”.leap indicator: “2-bit integer warning of an impending leap second to be inserted or deleted in the last minute of the current month.Note that I am NOT explaining the NTP algorithm at all, but only the packets and their fields that are present on the network. Looking on the wire you should understand the packet header ( section 7.3 in the RFC). Have a look at the current NTPv “Network Time Protocol Version 4: Protocol and Algorithms Specification” in order to understand the packets and protocol details. ![]()
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