Dynamic DNS

[Irina Goble]

> > 	What is the difference between A and PTR RRs?
> 
> Hmmmm.  Normally I would start to explain the difference between a DNS A
> and PTR record, but you know that, so I am not sure what you are asking.
> 
	Sorry, I had to say from ddns update's point of view.
	
> > I still think there should be only two transactions: add and delete.
> > 
> > 	ddns_add (lease)
> > 	ddns_delete (lease)
> 
> Hmmmm.  Perhaps.  Ted, since the dns-update() expression is your
> "brainchild"  :-) would care to jump in with reasoning, etc.  This
> non-atomicness of updates is starting to get ugly.  When a client roams
> from one subnet to another his new A record gets rejected because his old
> one is still in place.  I am thinking that perhaps a nsupdate(remove A)
> needs to be stacked on top of the nsupdate(add A), but I don't think you
> can remove an A record with NULL rdata to effect a removal of all names. 
> Do you know Irina?
> 
	You can remove all RR sets for a name with TYPE=ANY, TTL=0,
CLASS=ANY, RDLENGTH=0, RDATA=emtpy (there is no difference between A and
PTR RR updates :-) 
But from draft-ietf-dhc-dns-10 section 3.4.3:
	"The first rule in removing DNS entries is be sure that an
	antity removing a DNS enrty is only removing an enrty for 
	which it is responsible"
On the other hand, look at the problem with an opcode for a prerequisite
section in the current dhcpd: It should be NXDOMAIN instead of NXRRSET. 
For example if there is a CNAME RR for the name 
	www.test.com. IN CNAME www.anothertest.com.
a dyn. DNS update will break it. And draft-ietf-dhc-dns-10 says the
same in 3.4.1 - "the name does not exist". Once again:

	NXDOMAIN - "name is not in use"
	NXRRSET - "RR set does not exist"


> > on DHCPACK call ddns_add()
> > on DHCPRELEASE call ddns_delete()
> > on "ABANDON LEASE" call ddns_delete()
> > ddns_add can call ddns_delete to remove some leftovers.
> 
> I think some careful design needs to be done here to map out all of the
> possible reasons for adds/changes/deletes and make sure that we have all of
> the possibilities covered.  Impact on the DNS server is one of the items of
> major importance.  From having run a not very large but larger than average
> DHCP/DDNS service for a year, I can tell you that gratuitous updates to the
> DNS will kill your servers.  You need to only perform updates when they are
> absolutely necessary.
> 
	Agreed.
It could be nice to have asynchronous ddns support, doesn't it?
?