Re: [TICTOC] [ntpwg] WGLC on NTS: Why not run over IPsec?

[Kurt Roeckx <[e-mail]>]

On Wed, Mar 23, 2016 at 04:01:41AM -0400, Sharon Goldberg wrote:
> Dear WG,
> 
> Another question, and please forgive me if this was discussed already and I
> missed it.
> 
> It would be helpful to know why NTS is not just just running over IPsec. (I
> can see why running NTP over TLS makes little sense, since TLS runs over
> TCP while NTP runs over UDP so everything would probably
> break.) But NTP runs over IP. I suppose there are some performance
> hits to using IPsec? What are they?

I think the main problem is that they don't want that many IPsec
tunnels at the same time.  As far as I understand it, the design
wants to avoid storing this much state information on the server
side.  I'm not sure I agree with this design decision.

It could also use DTLS instead of TLS, which does work over UDP.

(D)TLS can already store the session on the client side, and
give that to the server on "resumption".  But maybe that would
require too many packets?

I'm also worried about the soundness of the crypto.  I have a
feeling this is designed by people that don't have enough
background to design something like this.  I think it needs to be
looked at by several people who do.  I've asked about this before
but nobody ever replied to it.


Kurt