[ntp:hackers] IEEE 1588 support in NTP?

Martin Burnicki martin.burnicki at meinberg.de
Fri Oct 28 03:41:30 PDT 2005


Our company Meinberg is offering a NTP time server which also works as a PTP 
grandmaster clock with a built-in hardware time stamp unit. We've recently 
participated in the IEEE-1588 meeting in Winterthur near Zurich/Switzerland. 
Part of that meeting was a plug-fest where PTP capable devices from different 
manufacturers were interconnected in order to see that they could work 
together. For more information please see our news article:

David D. Hagood wrote:
> Has any consideration been given to adding support for IEEE-1588
> Precision Time Protocol (PTP) into NTP?
> PTP (http://ieee1588.nist.gov/) is a standard for time synchronization
> over LAN for instrumentation - it is a part of the LAN extensions for
> Instrumentation (LXI - http://www.lxistandard.org/), and provides for
> time sync to tens of nanoseconds (YMMV - routers screw that up). The
> intended use is in a stack of instruments in a lab, connected to each
> other and to a PTP source via a local hub.
> The overall goals and methods of PTP are very much the same as NTP, and
> I'd hate to have to put both NTPD and PTPD
> (http://ptpd.sourceforge.net/) on the same machine as they would fight
> like cats and dogs over who was master - ideally you'd have one daemon
> doing both, and picking the "best" source.
> Where I work we are building gear that is Linux based (and so can have
> NTPD trivially) but I'd like to be fully LXI compliant which means
> supporting PTP as well (plus some of the stuff we do we need time sync
> to at worst hundreds of nanoseconds), and being a lazy cuss I'd rather
> see something like that in the mainstream NTPD rather than having to put
> it in myself on our own branch.

Please keep in mind that PTP yields an accuracy in the nanosecond range *only* 
if special network adapters with PTP support are used on all PTP nodes. 

PTP support for network adapters means that the adapters include a hardware 
timestamp unit which takes a time stamp whenever a PTP packet goes on the 
wire or is coming in from the wire. 

Without that hardware support PTP doesn't offer significantly more precision 
than NTP.

Martin Burnicki

Meinberg Funkuhren
Bad Pyrmont

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