RE : TR : Stepping back on the DNS discovery discussion

["BELOEIL Luc FTRD/DMI/CAE" <luc.beloeil@francetelecom.com>]

Hi Tim, 

Thanks you to react., My coments below

> -----Message d'origine-----
> De : Tim Chown [mailto:tjc@ecs.soton.ac.uk] 
> Envoyé : mercredi 16 juillet 2003 19:04
> À : dnsop@cafax.se
> Objet : Re: TR : Stepping back on the DNS discovery discussion
> 
> 
> On Wed, Jul 16, 2003 at 02:31:14PM +0200, BELOEIL Luc 
> FTRD/DMI/CAE wrote:
> > 
> > As DNS is a critical service between "applications world" and "IP 
> > layer world", we might be careful on consequences. From application 
> > point of view, we might ask in the future to extende that 
> solution to 
> > other type of services (NTP, ...). In that way, RA-based solution 
> > might not be the good solution, because I do think that RA 
> must not be 
> > extended to any sort of service discovery. Any idea about that?
> 
> So where do you draw the boundary between "network device 
> autoconfiguration" 
> and "service discovery".   For IPv4, you (manually or via 
> DHCP) configure
> IPv4 address, netmask, gateway and DNS resolver(s) as the 
> "basic" four 
> components to be able to get up and running.   In IPv6, when 
> using stateless 
> autoconfiguration, the RA mechanism takes care of the first 
> three (because 
> the stateless mechanism implies the /64 "netmask"), but the 
> DNS resolver 
> address(es) cannot be learnt (although I believe WinXP implements the 
> well-known site local discovery method).
> 
Yes indeed

> So an interesting question is what we mean by "stateless 
> autoconfiguration".
> I think this term is causing some of the religion in the 
> discussion :)   It 
> seems that probably mean "autoconfiguration without servers 
> (i.e. DHCPv6)", since there would have to be state 
> (pre-configuration) in the router (the 
> prefix configuration).   The RA camp seems to want the 
> routers to be able to
> issue DNS resolver information, not a separate full-blown 
> DHCPv6 server.
>
Hum as far as I understand DHCP-lite solution,DHCP-lite is also a stateless solution.
 
> But it's not that clear cut as, for example, my home DSL 
> router includes a DHCP server (as well my DNS server and 
> print server and other stuff). The functionality is combined, 
> all in a very cheap (<100 Euro) commodity box.
> 
How much a solution is , is only one side of the issue, not all -it depends so much of the market ;+). I do not discuss that.

> So are we really concerned as to whether we need a separate 
> DHCPv6 server on our network (and the overhead of that in 
> ad-hoc networks), or that we would 
> like a router to be able to provide DNS resolver information 
> on link (such that
> we can plumb networks without needing a separate DHCPv6 box)? 
>   If the latter, 
> then does it matter if the router does that via RA piggybacks 
> or DHCPv6 Lite? What is the real difference in implementation cost?
> 
Good question, I don't still know.

> Of course the mode of operation is also an interesting issue, 
> but it's possible for DHCPv6(Lite) to have an unsolicited 
> response mode added, if that is felt to be important.
> 
That solution must be investigate also.

> Something has to configure the prefix information to the 
> router, likewise the DNS information has to be configured.  I 
> don't think we've discusse that much, but distributing the 
> DNS resolver information to multiple routers rather than one 
> (or a small number of) DHCPv6 servers may require more 
> thought.  But in my home network, it'll all be in my DSL router :)
>

Some questions must still be investigated so that I could have a better opinion. 
- Can DHCP-lite work on the same link were there is a DHCP server, or a DHCP-relay?
- is DHCLP-lite with multicast extension is still DHCP? ;+)
- is RA-base solution actually much easier to implement? 
- How RA-based wil be implement, within the kernel, as a separate daemon?
...
 
> Tim

Luc

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