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

"Mark Atwood" <> Mon, 16 September 2019 22:35 UTC

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Date: Mon, 16 Sep 2019 15:35:25 -0700
From: "Mark Atwood" <>
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Subject: Re: [Ntp] =?utf-8?q?Antw=3A_Re=3A_Antw=3A_Re=3A_Calls_for_Adoption_-?= =?utf-8?q?-_NTP_Extension_Field_drafts_--_Four_separate_drafts?=
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On Sun, Sep 15, 2019, at 23:36, Hal Murray wrote:
> said:
> >> 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. 
> They are definitely not random.  They are unique.  (unless somebody screws up)
> Within a batch of Ethernet cards, they will probably be sequential.  (I'll say 
> more if anybody wants.)

In a past life, I've written the scripts that generate the mapping of manufacturing serial number to ethernet MAC addresses, and then generated the text files in the format requested by various manufacturing vendors so that they can fuse the MAC address into the device at manufacturing time, and so that the manufacturer and packaging vendors can print the necessary pcb labels and external case and box labels and barcodes.    And I've seen a lot of such other files that are sent to similar manufacturers.

I've never seen one that wasn't sequential.

The sequential relationship is so strong that it's used to identify supply chain and logistics glitches.

On the other other hand, you must not bet your life or your security on them being truly globally unique.   There are lots of chips in the supply chains and in warehouses that were manufactured off-label, grey market, unlicensed, and off-shift.   And anyone with kernel level or UEFI write level access to a box can persuade a chip or it's driver to lie about it's MAC.