Re: [Ntp] Antw: Re: Calls for Adoption -- NTP Extension Field drafts -- Four separate drafts
Heiko Gerstung <heiko.gerstung@meinberg.de> Wed, 28 August 2019 11:08 UTC
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Date: Wed, 28 Aug 2019 13:08:46 +0200
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Thread-Topic: [Ntp] Antw: Re: Calls for Adoption -- NTP Extension Field drafts -- Four separate drafts
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From: Heiko Gerstung <heiko.gerstung@meinberg.de>
To: Miroslav Lichvar <mlichvar@redhat.com>, "ntp@ietf.org" <ntp@ietf.org>
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Subject: Re: [Ntp] Antw: Re: Calls for Adoption -- NTP Extension Field drafts -- Four separate drafts
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Hi Miroslav, I do not think that it would add a lot of complexity if we would change the packet header format. Can you explain why you want to keep the 48 bytes length? Why is that so important? What would happen if the new v5 packet format would have, let's say, 56 bytes? Any implementation that wants to be v4/v5 compatible can easily deal with two different packet header formats IMHO. Handling this in the right way will not remotely add as much complexity as all the other v5 changes will cause. Think about the added complexity when someone has to implement the RefID handling as described in that draft, compared to just having an additional field in the packet that indicates there is a leap second smear going on, or there is a specific ID that you want clients to use when they refer to your server in their RefID field. Please do not get me wrong, I do not want to change the NTP packet format at any cost (or for the sake of change or to make it as hard as possible for implementors), I just want to avoid that we all try to stick with the current format (that arguably has some shortcomings, as illustrated by the presented drafts) just because we want to avoid that someone implementing NTPv5 has to add a second packet header structure to their code and, upon receiving or sending a packet, has to select which of the two formats to work with. This *exactly* is why there is a version field in the header, and it is placed very close to the start of the packet to make it efficient and secure for implementations to support multiple NTP versions. Again, lets change the NTP packet format for v5 to make things easier and less complex for future implementations. And do not stick with the format just because you want to avoid changing your own code too much, protect bad/faulty implementations or save firewall admins from having to touch their configuration. That said, I would be happy to start working on v5, maybe by collecting a list of all the issues and problems that we all see in v4 and the features we would like to see added. But maybe we should open another email thread for this. Best Regards, Heiko -- Heiko Gerstung Managing Director MEINBERG® Funkuhren GmbH & Co. KG Lange Wand 9 D-31812 Bad Pyrmont, Germany Phone: +49 (0)5281 9309-404 Fax: +49 (0)5281 9309-9404 Amtsgericht Hannover 17HRA 100322 Geschäftsführer/Management: Günter Meinberg, Werner Meinberg, Andre Hartmann, Heiko Gerstung Email: heiko.gerstung@meinberg.de Web: Deutsch https://www.meinberg.de English https://www.meinbergglobal.com Do not miss our Time Synchronization Blog: https://blog.meinbergglobal.com Connect via LinkedIn: https://www.linkedin.com/in/heikogerstung On 28.08.19, 12:39 "ntp im Auftrag von Miroslav Lichvar" <ntp-bounces@ietf.org im Auftrag von mlichvar@redhat.com> wrote: On Wed, Aug 28, 2019 at 12:07:53PM +0200, Heiko Gerstung wrote: > Regarding backwards compatibility of NTPv5: I think it would be no problem to change the NTP packet format if there are requirements we want to meet that can be fulfilled more efficiently with a changed packet header. Any implementation that ignores the version field deserves whatever happens to it and, since a client mode packet contains the version number, an NTP server would most probably have to reply to a v4 client request with a v4 server response anyway. Only if an implementation sends a request with version=5 and then tries to decode the response based on a v4 packet format there will be a problem. And again, implementations doing this should go down in flames anyway IMHO. I think a good reason to keep v5 mostly compatible with v4, similarly to how previous versions were compatible with one another, would be avoiding extra complexity in both server and client implementations. My suggestion would be to keep the NTP header 48 octets long and change only two fields: the refid and reference timestamp. They are ignored by current servers and most clients. That gives us 12 octets of contiguous space in the header to work with. That's plenty for the timescale negotiation and other metadata. Longer fields should be in extension fields. No MACs allowed. FWIW, I'm willing to help with the NTPv5 specification if people are considering to start working on that. -- Miroslav Lichvar _______________________________________________ ntp mailing list ntp@ietf.org https://www.ietf.org/mailman/listinfo/ntp
- [Ntp] Calls for Adoption -- NTP Extension Field d… Karen O'Donoghue
- Re: [Ntp] Calls for Adoption -- NTP Extension Fie… Heiko Gerstung
- [Ntp] Antw: Re: Calls for Adoption -- NTP Extensi… Ulrich Windl
- Re: [Ntp] Calls for Adoption -- NTP Extension Fie… tglassey@earthlink.net
- Re: [Ntp] Antw: Re: Calls for Adoption -- NTP Ext… Heiko Gerstung
- Re: [Ntp] Antw: Re: Calls for Adoption -- NTP Ext… Miroslav Lichvar
- Re: [Ntp] Antw: Re: Calls for Adoption -- NTP Ext… Miroslav Lichvar
- Re: [Ntp] Antw: Re: Calls for Adoption -- NTP Ext… Harlan Stenn
- Re: [Ntp] Antw: Re: Calls for Adoption -- NTP Ext… Heiko Gerstung
- Re: [Ntp] Antw: Re: Calls for Adoption -- NTP Ext… Miroslav Lichvar
- Re: [Ntp] Antw: Re: Calls for Adoption -- NTP Ext… Harlan Stenn
- Re: [Ntp] Antw: Re: Calls for Adoption -- NTP Ext… Heiko Gerstung
- Re: [Ntp] Antw: Re: Calls for Adoption -- NTP Ext… Miroslav Lichvar
- Re: [Ntp] Antw: Re: Calls for Adoption -- NTP Ext… Harlan Stenn
- Re: [Ntp] Antw: Re: Calls for Adoption -- NTP Ext… Harlan Stenn
- Re: [Ntp] Antw: Re: Calls for Adoption -- NTP Ext… Heiko Gerstung
- [Ntp] Antw: Re: Antw: Re: Calls for Adoption -- N… Ulrich Windl
- Re: [Ntp] Antw: Re: Calls for Adoption -- NTP Ext… Miroslav Lichvar
- Re: [Ntp] Calls for Adoption -- NTP Extension Fie… Daniel Franke
- Re: [Ntp] Antw: Re: Calls for Adoption -- NTP Ext… Heiko Gerstung
- Re: [Ntp] Antw: Re: Antw: Re: Calls for Adoption … Heiko Gerstung
- Re: [Ntp] Calls for Adoption -- NTP Extension Fie… Watson Ladd
- Re: [Ntp] Calls for Adoption -- NTP Extension Fie… Salz, Rich
- [Ntp] Antw: Re: Antw: Re: Calls for Adoption -- N… Ulrich Windl
- Re: [Ntp] Antw: Re: Calls for Adoption -- NTP Ext… Dieter Sibold
- Re: [Ntp] Calls for Adoption -- NTP Extension Fie… kristof.teichel
- Re: [Ntp] Antw: Re: Calls for Adoption -- NTP Ext… Magnus Danielson
- [Ntp] Antw: Re: Antw: Re: Calls for Adoption -- N… Ulrich Windl
- [Ntp] Antw: Antw: Re: Antw: Re: Calls for Adoptio… Ulrich Windl
- Re: [Ntp] Antw: Re: Calls for Adoption -- NTP Ext… Miroslav Lichvar
- Re: [Ntp] Antw: Re: Antw: Re: Calls for Adoption … Heiko Gerstung
- Re: [Ntp] Antw: Re: Antw: Re: Calls for Adoption … Hal Murray
- Re: [Ntp] Antw: Re: Antw: Re: Calls for Adoption … Miroslav Lichvar
- [Ntp] Antw: Re: Antw: Re: Calls for Adoption -- N… Ulrich Windl
- Re: [Ntp] Antw: Re: Antw: Re: Calls for Adoption … Harlan Stenn
- [Ntp] Antw: Re: Antw: Re: Antw: Re: Calls for Ado… Ulrich Windl
- [Ntp] Antw: Re: Antw: Re: Antw: Re: Calls for Ado… Ulrich Windl
- Re: [Ntp] Antw: Re: Antw: Re: Calls for Adoption … Heiko Gerstung
- Re: [Ntp] Antw: Re: Calls for Adoption -- NTP Ext… Harlan Stenn
- [Ntp] Antw: Re: Antw: Re: Antw: Re: Calls for Ado… Ulrich Windl
- Re: [Ntp] Antw: Re: Calls for Adoption -- NTP Ext… Heiko Gerstung
- Re: [Ntp] Calls for Adoption -- NTP Extension Fie… Miroslav Lichvar
- Re: [Ntp] Antw: Re: Calls for Adoption -- NTP Ext… Harlan Stenn
- Re: [Ntp] Antw: Re: Calls for Adoption -- NTP Ext… Magnus Danielson
- Re: [Ntp] Antw: Re: Antw: Re: Antw: Re: Calls for… Harlan Stenn
- Re: [Ntp] Antw: Re: Calls for Adoption -- NTP Ext… Heiko Gerstung
- Re: [Ntp] Antw: Re: Calls for Adoption -- NTP Ext… Harlan Stenn
- Re: [Ntp] Antw: Re: Calls for Adoption -- NTP Ext… Harlan Stenn
- Re: [Ntp] Antw: Re: Calls for Adoption -- NTP Ext… Daniel Franke
- Re: [Ntp] Antw: Re: Calls for Adoption -- NTP Ext… Miroslav Lichvar
- Re: [Ntp] Antw: Re: Calls for Adoption -- NTP Ext… Harlan Stenn
- Re: [Ntp] Antw: Re: Calls for Adoption -- NTP Ext… Heiko Gerstung
- Re: [Ntp] Antw: Re: Calls for Adoption -- NTP Ext… Hal Murray
- Re: [Ntp] Antw: Re: Calls for Adoption -- NTP Ext… Heiko Gerstung
- Re: [Ntp] Antw: Re: Calls for Adoption -- NTP Ext… Harlan Stenn
- Re: [Ntp] Antw: Re: Calls for Adoption -- NTP Ext… Harlan Stenn
- Re: [Ntp] Antw: Re: Calls for Adoption -- NTP Ext… Heiko Gerstung
- Re: [Ntp] Antw: Re: Antw: Re: Calls for Adoption … Hal Murray
- Re: [Ntp] Antw: Re: Antw: Re: Calls for Adoption … Miroslav Lichvar
- Re: [Ntp] Antw: Re: Antw: Re: Calls for Adoption … Heiko Gerstung
- [Ntp] Antw: Re: Antw: Re: Antw: Re: Calls for Ado… Ulrich Windl
- [Ntp] Antw: Re: Antw: Re: Antw: Re: Calls for Ado… Ulrich Windl
- Re: [Ntp] Antw: Re: Antw: Re: Antw: Re: Calls for… Watson Ladd
- Re: [Ntp] Antw: Re: Calls for Adoption -- NTP Ext… Salz, Rich
- Re: [Ntp] Antw: Re: Calls for Adoption -- NTP Ext… Daniel Franke
- Re: [Ntp] Antw: Re: Calls for Adoption -- NTP Ext… Salz, Rich
- Re: [Ntp] Antw: Re: Calls for Adoption -- NTP Ext… Daniel Franke
- Re: [Ntp] Antw: Re: Calls for Adoption -- NTP Ext… Salz, Rich
- Re: [Ntp] Antw: Re: Calls for Adoption -- NTP Ext… Salz, Rich
- [Ntp] NTP errors Hal Murray
- Re: [Ntp] Calls for Adoption -- NTP Extension Fie… Harlan Stenn
- [Ntp] Antw: Re: Antw: Re: Calls for Adoption -- N… Ulrich Windl
- Re: [Ntp] Antw: Re: Antw: Re: Calls for Adoption … Watson Ladd
- Re: [Ntp] Antw: Re: Antw: Re: Calls for Adoption … Hal Murray
- [Ntp] Antw: Re: Antw: Re: Antw: Re: Calls for Ado… Ulrich Windl
- Re: [Ntp] Antw: Re: Calls for Adoption -- NTP Ext… Miroslav Lichvar
- Re: [Ntp] Antw: Re: Calls for Adoption -- NTP Ext… Hal Murray
- Re: [Ntp] Antw: Re: Calls for Adoption -- NTP Ext… Miroslav Lichvar
- Re: [Ntp] Calls for Adoption -- NTP Extension Fie… Fernando Gont
- Re: [Ntp] Antw: Re: Calls for Adoption -- NTP Ext… Miroslav Lichvar
- [Ntp] Antw: Re: Antw: Re: Calls for Adoption -- N… Ulrich Windl
- Re: [Ntp] Antw: Re: Antw: Re: Calls for Adoption … Harlan Stenn
- Re: [Ntp] Antw: Re: Antw: Re: Calls for Adoption … Miroslav Lichvar
- [Ntp] Antw: Re: Antw: Re: Antw: Re: Calls for Ado… Ulrich Windl
- Re: [Ntp] Antw: Re: Antw: Re: Antw: Re: Calls for… Watson Ladd
- Re: [Ntp] Antw: Re: Antw: Re: Calls for Adoption … Hal Murray
- Re: [Ntp] Antw: Re: Antw: Re: Calls for Adoption … Mark Atwood
- Re: [Ntp] Antw: Re: Antw: Re: Calls for Adoption … Steven Sommars
- [Ntp] Antw: Re: Antw: Re: Antw: Re: Calls for Ado… Ulrich Windl