Service discovery (was Re: [Sks-devel] pool.sks-keyservers.net DNS unresponsive?)

[David Shaw]

On Jul 2, 2009, at 11:31 PM, Phil Pennock wrote:

> On 2009-07-02 at 14:00 -0400, Daniel Kahn Gillmor wrote:
> > I appear to be getting no A records for pool.sks-keyservers.net.   
> > this
> > seems like a Bad Thing.
> >
> > is anyone else seeing this?  it's forcing my nameservice resolution  
> > to
> > fall back to IPv6, which is link-local only for a number of my  
> > machines
> > which don't have connections to any of the IPv6 tunnel brokers.
>
> I see it too.
>
> FWIW, which isn't that much, if you want a temporary workaround you  
> can
> use keys.sks.pool.globnix.net -- however, that makes no attempt to
> subset the results, so DNS will fall back to TCP.  It does not include
> 1.0.10 servers.  There's also keys.ipv4.sks.pool.globnix.net and
> keys.ipv6.sks.pool.globnix.net.  I didn't bother coming up with nicer
> names as this was just me exploring what I could do and coming up with
> names which exist but aren't so likely to be memorable and detract  
> from
> the existing pools.

On the subject of the various "pool" keyserver addresses, I'm working  
on (re) adding SRV support to GPG using DNS service discovery.  This  
will allow for a much richer pool description, as it is possible to  
group servers in tiers and also to weight servers within a given tier,  
unlike the current system which is strictly round-robin.  (You can say  
things like "Here are 10 servers, grouped in 3 tiers of 3, plus an  
additional tier of 1.  Pick such-and-such server from such-and-such  
tier 50% of the time, and the other two in that tier 25% of the time  
each.  Only go to the next tier if everything in the initial tier is  
down.").  It means that the pool creator can bias the server choice  
towards faster/better-connected machines.  Also useful is that it  
allows servers to run on something other than port 11371 without  
having to tell everyone about the new port as the service discovery  
returns the port as part of the lookup.

David