[dns-operations] Comparing TCP and UDP response times of root name servers

Tony Finch dot at dotat.at
Wed Nov 21 15:07:00 UTC 2012

John Kristoff <jtk at cymru.com> wrote:
> On Wed, 21 Nov 2012 14:19:02 +0000
> Tony Finch <dot at dotat.at> wrote:
> > I doubt it would provide any advantage compared to DNS over TCP.
> Your doubt isn't very convincing to me, but I'm not inclined to argue
> too strenuously that it would be worth doing in lieu of just utilizing
> TCP.

I should probably expand, then. The difference between DCCP and TCP is it
leaves it to the application to handle packet loss and re-ordering.
DNS-over-TCP allows re-ordering of application-level responses so it
avoids some of the head-of-line blocking problem. DNS-over-DCCP would have
to reimplement some kind of truncation/retry logic. It would not have
UDP's advantages of no setup latency and minimal kernel state - it doesn't
seem very much lighter than TCP.

> [...] would help address the problem if something like DCCP were to
> supplant UDP.

There's the rub :-)

f.anthony.n.finch  <dot at dotat.at>  http://dotat.at/
Forties, Cromarty: East, veering southeast, 4 or 5, occasionally 6 at first.
Rough, becoming slight or moderate. Showers, rain at first. Moderate or good,
occasionally poor at first.

More information about the dns-operations mailing list