DNS Query Behavior with Global Forwarders Statement

[Mark Andrews]

> > Is this an artifact of the -P2 changes or was the use of RTT dropped  
> > for some other reason?
> 
> You didn't say which version you were running.
> 
> I'd be quite surprised if this were an artifact of the -P1 and -P2
> changes.  I'd be less surprised if it were a bug introduced in 9.5.0.
> 
> --
> Evan Hunt -- evan_hunt at isc.org
> Internet Systems Consortium, Inc.

	RTT estimates work well with authoritative servers.

	The best I expect to get out of rtt and forwarders is whether
	the forwarder is up or not.  If there was some way to
	accurately work out which answers come from the cache and
	which first required recursion then rtt times would home
	in the closest forwarder.

	It takes 110ms to get a answer from A via F1 and F2.

			R 10ms F1 100ms A
			R 100ms F2 10ms A

	Cache talking to caches don't always get enough second level
	cache hits to make a statistical difference to the rtt estimate.

	Mark
	
-- 
Mark Andrews, ISC
1 Seymour St., Dundas Valley, NSW 2117, Australia
PHONE: +61 2 9871 4742                 INTERNET: Mark_Andrews at isc.org