NTP

showstack / protocols / ntp

Also called Network Time Protocol, NTPv4, SNTP.

The protocol that keeps ordinary computers agreeing about the time of day. It corrects for network delay by measuring the round trip and disciplines the local clock gradually rather than jumping it. Milliseconds on a good LAN — nowhere near PTP, and exactly right for its actual job: making logs, licences and scheduled events line up across a rack.

Timecode and syncOpenIETFVerified

Management Housekeeping, no deadline

Discovery, monitoring, configuration, backups, updates. Useful, and none of it has a deadline of its own.

What kills it. Nothing kills it. That is the problem: with no deadline it has no manners, and it will happily starve everything that does have one. Putting it on a show VLAN is the commonest self-inflicted wound in the industry.

Why this one, and not what the category suggests. Wall-clock agreement to within milliseconds. Useful for log timestamps, nowhere near tight enough to be a show clock — a distinction people lose money on.

The four flows, and why the model is worth having →

Ports

udp/123 NTP client and server
Symmetric: both ends use 123 in the classic mode. Blocking it outbound is a common cause of machines that slowly drift apart.

What goes wrong

NTP is not a substitute for PTP, LTC or genlock. It gives a machine the right time of day; it does not lock media clocks and cannot align a frame or a sample.

Two time sources on one network is the classic fault: a show LAN with no internet and a machine still pointed at a public pool will drift away from everything else, or step suddenly when it finally reaches one.

Give an isolated show network its own NTP server — a switch, a router, a master clock or a GNSS receiver — rather than leaving each machine to guess.

Windows domain time and NTP are related but configured differently, and a machine that has joined a domain may quietly ignore the server you set.

A step correction rather than a slew can jump a clock backwards, which breaks anything measuring elapsed time. Prefer a source that lets the daemon discipline gradually.

What speaks NTP (1)

Product	Direction	Notes
Evertz 5601MSC Master Sync and Clock Evertz	out	Time of day for the facility.

Typical use

Keeping show machines, media servers and consoles on the same wall-clock time so logs can be compared after a fault.
Time-stamping recordings, captures and measurement sessions.
Satisfying licensing and certificate checks that fail silently when a machine believes it is in 1970.
Scheduling in installations — building systems, digital signage, unattended playback.

Sources

RFC 5905: Network Time Protocol Version 4 — IETF primary

Understand the mechanism

How it all runs together How a one gets down a wire

Something wrong, or missing?

Known gaps on this entry: implementations. If you can source one of them, that is a ten minute pull request.

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