[dns-operations] caches only resetting TTL? was Re: Where to find "DNS resolution path corruption"?

[Mark Andrews]

> > So I'm curious where this behaviour originates from, so I have a stick to
> > beat the ISP's to delete old authoritative zones.

	The cache is only doing what it is designed to do.  Cache
	the responses.  In this case it's caching the authoritative
	part of the response.  Each time it gets a answer it gets
	a new copy of the NS RRset for the zone and it caches it.

	The caching server assumes that correct management practices
	are being followed.  That old server will serve the current
	zone content (which is what should happen for a period) or
	that the old server is not serving the zone.

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