[ietf-dkim] Re: Replay attacks, what's that?

[Tony Finch]

On Sat, 6 Aug 2005, Douglas Otis wrote:
>
> User-keys in DNS could have a significant impact on DNS traffic.  When
> compared to the overall traffic carried by the the messages, this would
> represent just a percentage of increase.  But when considering the
> impact on DNS cache, the effects could be far greater.  Perhaps one
> solution for protecting the DNS cache would be to severely limit any TXT
> or KEY record's TTL.  However, short TTLs for user-keys AND domain-keys
> would impact the overall performance of email, as every operation would
> likely suffer a DNS lookup, with perhaps an increase in the already high
> DNS response loss rate.  With long time-outs and damage to DNS cache,
> the affect that user-keys may have on DNS could be damaging other
> applications as well.

DNS performance depends on the cacheing of NS records, not leaf records,
so forcing short TTLs on DKIM records won't have much impact.

Tony.
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