[ih] History of duplicate address tests

[Andrew G. Malis]

Joe,

Since ARP preceded DHCP by about a decade, give or take, early IP address
duplication would most likely have been the result of manual
misconfiguration. Having such  misconfiguration as visible as possible
would have been a good thing so that it could be quickly corrected.

Cheers,
Andy

On Tue, Nov 29, 2022 at 3:50 PM touch at strayalpha.com <touch at strayalpha.com>
wrote:

> Hi, Andy,
>
> Using ARP as duplicate address detection has an unintended and possibly
> dangerous consequence.
>
> If you ARP your own address, you are also broadcasting the IP/Ethernet
> association of your endpoint as the requesting party. That can flush caches
> elsewhere and cause traffic to the previous owner of that endpoint to fail
> - in some cases (and surprisingly) that includes the endpoint that had that
> address in the first place.
>
> So I don’t think that qualifies as “safe” duplicate address detection and
> I wouldn’t say that this would be an origin of that concept, as a result.
>
> YMMV.
>
> Joe
>
> —
> Dr. Joe Touch, temporal epistemologist
> www.strayalpha.com
>
> On Nov 29, 2022, at 12:43 PM, Andrew G. Malis via Internet-history <
> internet-history at elists.isoc.org> wrote:
>
> John,
>
> ARP (RFC 826) trivially enables duplicate IPv4 address detection on
> Ethernet networks (just ARP for your own address and see if anyone else
> responds), so I guess November 1982 for IP over Ethernet.
>
> Cheers,
> Andy
>
>
> On Tue, Nov 29, 2022 at 3:23 PM John Kristoff via Internet-history <
> internet-history at elists.isoc.org> wrote:
>
> My earliest memory, because that is the time of my entry into the
> field, of duplicate address detection was done on Token Ring networks
> during ring insertion (phase 2 - address verification).  More recently
> IPv6 has duplicate address detection (dad).
>
> I'm curious to know about the earliest of duplicate address detection
> mechanisms.  I imagine there were some predating what I remember about
> Token Ring, but this is the kind of thing that is difficult to uncover
> without some hints. Any pointers to the earliest of these functions in
> networking?
>
> Thanks kindly,
>
> John
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