[Ntp] Antw: Re: Antw: Re: Antw: Re: Calls for Adoption -- NTP Extension Field drafts -- Four separate drafts

"Ulrich Windl" <Ulrich.Windl@rz.uni-regensburg.de> Wed, 04 September 2019 10:27 UTC

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Date: Wed, 04 Sep 2019 12:27:10 +0200
From: "Ulrich Windl" <Ulrich.Windl@rz.uni-regensburg.de>
To: "ntp@ietf.org" <ntp@ietf.org>, "Heiko Gerstung" <heiko.gerstung@meinberg.de>,<mlichvar@redhat.com>
References: <mlichvar@redhat.com> <20190902095854.GC15024@localhost> <20190903120544.394CC40605C@ip-64-139-1-69.sjc.megapath.net> <20190904095111.GJ15024@localhost> <93C7B33D-8B6C-4FDF-A55E-7B20AB7B03BE@meinberg.de> <A7C4D27502000083822C0D04@gwsmtp.uni-regensburg.de> <D5F28766020000316A6A8CFC@gwsmtp.uni-regensburg.de> <2E18D20E0200009A822C0D04@gwsmtp.uni-regensburg.de> <4B834D170200006586EDC2A6@gwsmtp.uni-regensburg.de> <831B91BE020000B87ED719BE@gwsmtp.uni-regensburg.de> <5D6CB84E020000A100033405@gwsmtp.uni-regensburg.de> <6A31A7C90200006043047E14@gwsmtp.uni-regensburg.de> <87F2C84C0200007A6A6A8CFC@gwsmtp.uni-regensburg.de> <0A3D67B1020000F643047E14@gwsmtp.uni-regensburg.de> <6FF2BC4A020000476A6A8CFC@gwsmtp.uni-regensburg.de> <B23647160200000E86EDC2A6@gwsmtp.uni-regensburg.de>
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Subject: [Ntp] Antw: Re: Antw: Re: Antw: Re: Calls for Adoption -- NTP Extension Field drafts -- Four separate drafts
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>>> Heiko Gerstung <heiko.gerstung@meinberg.de> schrieb am 04.09.2019 um 12:05
in
Nachricht <93C7B33D-8B6C-4FDF-A55E-7B20AB7B03BE@meinberg.de>de>:
> Using a Ethernet mac address or an IP address will allow to identify a
server 
> if it is included in the "sync chain" data set, I therefore would 
> definitively go for a random ID. I am not yet decided if it should be
allowed 
> to let the user assign a static ID via configuration as that would make 
> duplicates/collisions more likely than the random ID approach. 

It there an RFC about "Operators aren't allowed to do silly things" already?
;-)
Maybe the default (recommended setting) should be random on every daemon
start, but I do not like seemingly arbitrary restrictions...

Regards,
Ulrich

> 
> Regards, 
>     Heiko
> 
> 
> On 04.09.19, 11:52 "ntp im Auftrag von Miroslav Lichvar" 
> <ntp-bounces@ietf.org im Auftrag von mlichvar@redhat.com> wrote:
>> 
>> On Tue, Sep 03, 2019 at 05:05:44AM -0700, Hal Murray wrote:
>>> I think there are two approaches.
>>> 
>>> One is to use random data. The probability of a collision can
>>> be made 
>>> arbitrarily small by making the number of bits in the ID big
>>> enough. That 
>>> needs good randomness.
>>> 
>>> The other approach is to piggyback on some other scheme that
>>> has already 
>>> solved the problem.
>> 
>> The former makes more sense to me. We don't need the ID to be
>> static.
>> Generating a random number on each start should be fine.
>> 
>>> Can we assume that every server will have a globally routeable
>>> IPv6 address? 
>> 
>> No. IPv6 is not universally available. Address translation is
>> common, so we cannot assume an IPv4 or IPv6 address is unique.
>> 
>>> Can we assume that every server will have an Ethernet host address?
>> 
>> The vast majority will, but I'm not sure we can rely on them
>> being random.
>> 
>>> In both cases, for multi homed servers, just pick one. After
>>> that choice, 
>>> it's an ID, no longer an address.
>> 
>> Yes. And it's important that all clients get the same ID.
>> 
>> -- 
>> Miroslav Lichvar
>> 
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> 
> 
> 
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