{"id":962,"date":"2008-11-06T09:00:44","date_gmt":"2008-11-06T09:00:44","guid":{"rendered":"https:\/\/www.galsys.co.uk\/news\/?p=962"},"modified":"2011-11-02T13:41:53","modified_gmt":"2011-11-02T13:41:53","slug":"ntp-time-server-packet-header-explained","status":"publish","type":"post","link":"https:\/\/www.galsys.co.uk\/news\/ntp-time-server-packet-header-explained\/","title":{"rendered":"NTP Time Server Packet Header Explained"},"content":{"rendered":"

Most time servers use Network Time Protocol <\/a>and like other Internet based protocols NTP contains a packet header. A packet header, put simply, is just is a formatted unit of data that describes the information contained in the packet.<\/p>\n

The NTP packet header consists of a number of 32-bit words. Here is a list of the most common packet header terms and their meaning:<\/p>\n

IP address \u2013 the address of the NTP Time Server <\/a><\/p>\n

NTP Version \u2013 which version of NTP (currently version 4 is the most recent)<\/p>\n

Reference timestamp (the prime epoch ) used by NTP to work out the time from this set point (normally January 01 1900<\/p>\n

Round trip delay (the time it takes request to arrive and come back in milliseconds)<\/p>\n

Local clock offset \u2013 time difference between host and client<\/p>\n

Leap indicator (if there is to be a leap second that day \u2013normally only on 31 December)<\/p>\n

Mode3\u00a0 –\u00a0 a three bit integer which values represent: 0=reserved, 1=symmetric active, 2= symmetric passive, 3=client, 4=server, 5=broadcast, 6=NTP control message, 7=reserved for private use.<\/p>\n

Stratum level \u2013 which stratum level the NTP server <\/a>is (a stratum 1 server receives the time from an atomic clock source a stratum 2 server receives the time from a stratum 1 server)<\/p>\n

Poll Interval (How many requests is made and their intermittence)<\/p>\n

Precision \u2013 how accurate in milliseconds is the system clock<\/p>\n

Root Delay \u2013 This is a signed fixed-point number indicating the total roundtrip delay to the primary reference source at the root<\/p>\n

Root dispersion (in milliseconds)- The root dispersion is the maximum (worst case) difference between the local system clock and the root of the NTP tree (stratum 1 clock)<\/p>\n

Ref ID \u2013 32 bit identifying the reference clock<\/p>\n

Originate time stamp (time before synchronisation request)<\/p>\n

Receive timestamp \u2013 the time the host\/NTO time Server got the request<\/p>\n

Transmit timestamp \u2013 the time the host sent back the request<\/p>\n

Valid\u00a0 response\u2013 is the system clock\u00a0 synchronised or not<\/p>\n","protected":false},"excerpt":{"rendered":"

Most time servers use Network Time Protocol and like other Internet based protocols NTP contains a packet header. A packet header, put simply, is just is a formatted unit of data that describes the information contained in the packet. The NTP packet header consists of a number of 32-bit words. Here is a list of…<\/p>\n

Continue reading <\/i><\/a><\/p>\n","protected":false},"author":4,"featured_media":0,"comment_status":"closed","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[3,7,8,9,13],"tags":[19,20,207,126,25,68,26,27,28,204,29,30,205,34,35],"class_list":["post-962","post","type-post","status-publish","format-standard","hentry","category-advanced-ntp","category-ntp-basics","category-ntp-configuration","category-ntp-server-2","category-time-synchronisation","tag-gps-ntp-server","tag-gps-ntp-time-server","tag-gps-time-server","tag-linu","tag-network-time-server","tag-ntp","tag-ntp-clock","tag-ntp-gps-server","tag-ntp-gps-time-server","tag-ntp-server-2","tag-ntp-servers","tag-ntp-time-server","tag-time-server","tag-windows-ntp-server","tag-windows-server-2008"],"yoast_head":"\nNTP Time Server Packet Header Explained - Galleon Systems<\/title>\n<meta name=\"robots\" content=\"index, follow, max-snippet:-1, max-image-preview:large, max-video-preview:-1\" \/>\n<link rel=\"canonical\" href=\"https:\/\/www.galsys.co.uk\/news\/ntp-time-server-packet-header-explained\/\" \/>\n<meta property=\"og:locale\" content=\"en_US\" \/>\n<meta property=\"og:type\" content=\"article\" \/>\n<meta property=\"og:title\" content=\"NTP Time Server Packet Header Explained - Galleon Systems\" \/>\n<meta property=\"og:description\" content=\"Most time servers use Network Time Protocol and like other Internet based protocols NTP contains a packet header. 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