[sclug] Sticky DNS Glue.

[James Fidell]

Quoting Roland Turner (raz.fpyht.bet.hx at raz.cx):

> For the vast majority of
> situations, the glue is not neccessary, but other than for
> delegations managed by particularly clueless registrars
> (easily.co.uk springs to mind), it is ordinarily included to
> provide performance and reliability improvements.

I think you'll find the general case is actually the opposite.

Listing specific glue records for a domain where the nameservers
are outside of the domain (and particularly where the domains
containing the nameservers aren't managed by you) is a major
pain and things will generally work a lot better if you *don't*
list glue records where nameserver addresses are outside your
control.

Consider, for example, you being a registrar listing my nameservers
for a domain.  How do you deal with me changing the IP addresses of
my nameserver?  You have to rebuild your zone files, checking the
addresses for my nameservers each time.  How often do you do that?

I can wind down the TTL on my zone files running up to any IP address
change for my nameservers, helping people pick up the new records as
soon as possible.  After the change, you'll be giving out invalid data
until such time as you rebuild the zone files, so this actually makes
DNS less reliable.

Performance-wise, most people will have cached the NS data after the
first query anyway, so whilst there's a small performance gain from
having glue records, it's not that significant.

You gave the example of easily.co.uk as a clueless registrar who doesn't
list glue records.  I'm not necessarily going to disagree with the
clueless bit, but let's check out a few others.  Your own domain,
for instance.  The .cx registry doesn't hold glue records for its
nameservers.  How about someone bigger?  Say, Nominet?  They do hold
glue records for all my .uk domains, but only because my nameservers
appear inside a .uk domain anyway and therefore the glue records are
required to exist.  They don't carry glue records where the nameservers
are, say, in .com or .net.

James