Re: [dnsext] Re: RFC 3484 section 6 rule 9 causing more operational problems

[Paul Vixie <[e-mail]>]

> The NTP issue is rather specific and affected ntpd when you had
> 
> server pool.ntp.org
> server pool.ntp.org
> server pool.ntp.org
> 
> in your configuration.
> 
> And some those mirrors I mentioned are affected by *deterministic*
> reordering.  They don't care if traffic hits the closest instance,
> they want to spread the load (security.debian.org, for instance, is
> difficult to serve from a single node from time to time).

thanks for explaining that.

> > and the nameserver examples you gave are all subject to rdns RTT
> > sorting.
> 
> If you follow Rule 9, you haven't got that many RTTs to sort by: Rule
> 10 ensures that there is a single IP address you should use as long as
> the service on it is reachable.  Unless you cheat, deviate from Rule
> 9, contact additional servers, and gather additional RTTs--but you
> have to cheat to get that data.

i don't know any recursive nameservers that follow RFC 3483 for authority
server selection?  (your example here was of authority nameservers.)

> > and they have to use drastically low TTL's to prevent mobility from
> > breaking their assumptions.  and they have no way to cope with opendns
> > or any other global or semi-coherent caching layer.  and even when they
> > use TTL=0 and happen to be talking to an rdns who shares topology with
> > the stub, they're making an educated guess without knowing what kinds
> > of wormholes the stub may have access to, whether VPN, private
> > interconnects that don't show up in global BGP, or whatever.
> 
> Well, if it's not a good idea, why are most large web sites served
> this way?

nobody ever got fired for buying $whatever.  so: great marketing trumps
any kind of engineering whether good or bad.

> I suspect there is currently no better way to distribute initial
> client requests than to play DNS tricks.

since the web protocols support both permanent and temporary redirects,
i've always preferred approaches like IBM's over approaches like akamai's.