Re: key length & fragmentation

["Scott Rose" <scottr@antd.nist.gov>]

Personally, I think key lengths should be chosen for security reasons, not
DNS server implementation reasons.  However, since any DNSSEC aware
resolver/server should also be EDNS aware, so truncation/fragmentation will
be a worry when big keysets are in the picture (multiple algorithms, etc).

In the tests - what were the average size of the KEY RRsets?

OTOH, I don't see why having a shorter key (that may have to be rolled over
more often) is less secure than a longer key.  The operational lifetime of a
key can be measured by how much data is has to sign and how often it resigns
the zone data.  There are guidelines in some hardcore security policies from
NSA/DoD - I can't name the off hand.

Short answer - "no" I don't think operational issues should dictate key
lengths, but huge keys don't necessarily mean more secure either :)

Scott
----- Original Message -----
From: "Bill Manning" <bmanning@isi.edu>


> resend from last week.
>
>
>         putzing about with keys of various lengths shows that
>         when keys are over a certain size, UDP fragmentation sets
>         in,  In some cases, it is possible to actually get rollover
>         to TCP (although this seems to be a corner case)
>
>         now I've been told that UDP fragmentation can be a bad thing,
>         leading to all sorts (well some kinds anyway) of odd
>         operational failures that are hard to debug.  UDP failure
>         and rolling over to TCP is also considered a bad thing.
>
>         so this question, "should key lengths be selected to
>         avoid fragmentation/TCP use?"
>
>         if so, why?
>         if not, why not?
>
>
> --
> --bill