barmar at alum.mit.edu
Wed Jan 26 05:58:04 UTC 2011
In article <mailman.1499.1296009856.555.bind-users at lists.isc.org>,
pyh at mail.nsbeta.info wrote:
> I'm reading the document "Secure DNS Deployment Guide" got from the URL a
> poster gave in the list.
> The document said:
> When a user types the URL www.example.com into a Web browser, the browser
> program contacts a type of resolver called a stub resolver that then
> contacts a local name server (called a recursive name server or resolving
> name server). The resolving name server will check its cache to determine
> whether it has valid information (the information is determined to be valid
> on the basis of criteria described later in this document) to provide IP
> address for the accessed Internet resource
> (i.e.,www.marketing.example.com). If not, the resolving name server checks
> the cache to determine whether it has the information regarding the name
> server for the zone marketing.example.com (since this is the zone that is
> expected to contain the resource www.marketing.example.com). If the name
> server!Ës IP address is in the cache, the resolver!Ës ne query will be
> directed against that name server. If the IP address of the name server of
> marketing.example.com is not available in the cache, the resolver
> determines whether it has the name server information for a zone that is
> one level higher than marketing.example.com (i.e., example.com). If the
> name server information for example.com is not available, the next search
> will be for the name server of the .com zone in the cache.
> I think the statement below is wrong?
> > If not, the resolving name server checks the cache to determine whether it
> > > has the information regarding the name server for the zone
> > marketing.example.com (since this is the zone that is expected to contain >
> > the resource www.marketing.example.com).
> How does the resolver know www.marketing.example.com is a domain name or a
> zone? www.marketing.example.com can also be a zone which has valid NS
> records. So I was thinking the resolver shall check the cache firstly to
> see whether it has the NS records for the zone www.marketing.example.com,
> if not, then to check the NS for marketing.example.com. Am I right?
Barry Margolin, barmar at alum.mit.edu
*** PLEASE don't copy me on replies, I'll read them in the group ***
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