Re: IPv6 Routing & ND vs. Addressing, (Was: Re: <draft-ietf-6man-rfc4291bis-09.txt>)

[Brian E Carpenter <[e-mail]>]

On 16/07/2017 01:39, Philip Homburg wrote:
>> This is backwards. The goals of pseudo-random IIDs are to reduce the
>> probability that scanning attacks find hosts, and to reduce the risk
>> of IIDs being used to breach privacy.
>>
>> If these goals are met, the collision probability will in any case
>> be low, so DAD failure will be exceedingly rare.
> 
> I completely disagree. A collision is fatal. We are nowhere near transparently
> handling all collisions. At best we can hope that DAD can make one node
> continue unaffected.

I'm confused.

Firstly, do we have any experimental evidence that collisions
are a real operational problem? (Obviously, MAC address collisions are
disastrous at layer 2 anyway, so although IPv6+(Modified EUI-64) needs to
detect them, they are irrelevant to the current discussion.)

Secondly, if a collision does occur with IPv6+(pseudo-random IID),
recovery is obvious: after DAD failure, generate a new pseudo-random
IID and try again. This is perfectly compatible with RFC4862 section 5.5
and is specfied in RFC7217 for stable IIDs and in RFC4941 for privacy
addresses.

    Brian

> 
> In contrast, people have been scanning my IPv4 ranges for the past 20 years
> or so. That may be annoying. That may amplify attacks opportunities. But
> in it self it is not fatal.
> 
> 
> .
>