Re: [ntpwg] [dhcwg] Re: Network Time Protocol (NTP) OptionsforDHCPv6

[Danny Mayer <[e-mail]>]

Ted Lemon wrote:
> On Nov 27, 2007, at 4:00 PM, David L. Mills wrote:
>> If the DHCP server followed that advice, it would
>> occasionally re-resolve the name and pass the new IP address to its
>> clients.  It is not at all clear that this advice is followed in the real
>> world.
> 
> It is followed, actually.   E.g., the Nominum DHCP server (DCS) just
> looks the name up every time, under the assumption that the caching name
> server is going to perform better than any ad hoc resolver we might
> stuff into the DHCP server.   The ISC DHCP server caches names for an
> hour - a decision I made when caching name servers weren't as good as
> they are now, and when I was a lot more naive about DNS than I am now. 
> I can't speak for the other vendors, so you'd have to ask them, but I'd
> be really surprised if they didn't do the same thing - if you cache the
> value, you have to cache it some/where/ - it's not quite the same as
> when a server looks up an address in the DNS so that it can connect to
> that address.
> 

This was the next question to ask of course. How many of the addresses
in the reply are cached for distribution as appropriate? With the pool
config option we use as many as 10 returned from the DNS query. How many
of these would we expect to get if we relied on DHCP to supply those IP
addresses.

> I don't know what SOHO routers do, in general - it would be interesting
> to investigate.

Volunteers?

Danny

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