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authorcvs2svn <cvs2svn@FreeBSD.org>2002-07-01 01:08:00 +0000
committercvs2svn <cvs2svn@FreeBSD.org>2002-07-01 01:08:00 +0000
commitb65d5f103dafa5c2237518f25b6790926c29f4ed (patch)
parent06346a957f7ae00f08f0360f681b76988a9982f1 (diff)
This commit was manufactured by cvs2svn to create branch 'RELENG_4_4'.
Notes: svn path=/releng/4.4/; revision=99184
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+Message-Id: <200005230246.WAA03750@hrothgar.gw.com>
+To: ...
+Subject: Notes on RFC-2317
+Date: Mon, 22 May 2000 22:46:55 -0400
+From: Kimmo Suominen <kim@tac.nyc.ny.us>
+I wrote down some notes on RFC-2317. I've had discussions with all of
+you regarding classless IN-ADDR.ARPA delegations, and I would very much
+appreciate any comments you may have. Please feel free to forward this
+to other parties as you see necessary or appropriate.
+The goal of these notes is to try and clarify the reasoning behind the
+recommendations I've been making on implementing RFC-2317 delegations.
+In particular the following issues keep coming up with again and again
+with each vendor:
+ - why use "-" instead of "/"
+ - why use particular NS records
+ - why delegate within IN-ADDR.ARPA
+I am hoping that the these notes could eventually be used to convince
+ISPs to provide an efficient and smooth implementation of RFC-2317 with
+the least amount of headache for the end-user.
++ Kim
+1. Selecting the CNAME target zone
+ RFC-2317 shows an example case where the target zone is a delegated
+ sub-zone of the IN-ADDR.ARPA zone for the natural class C network.
+ This will allow for the NS records for the zone can be independently
+ selected (see benefits described below). An example of such a zone
+ would be 0-
+ Now pay careful attention to the last paragraph of RFC-2317. There
+ are broken resolver implementations that apply the "valid host name"
+ restrictions on the CNAME target (it should only be applied to the
+ PTR target name). To avoid problems with such implementations it
+ is best to use a character that is allowed in a hostname. I prefer
+ using a hyphen, as I did in the example above.
+ Some ISPs may at first refuse to delegate these zones (without any
+ explanation). Approach such ISPs with the reasoning in here first,
+ but if that fails consider using your "forward" zone as a fallback.
+ There is nothing magic about the IN-ADDR.ARPA zone for RFC-2317
+ delegations. You will have to sacrifice the optimization provided
+ by a correct IN-ADDR.ARPA delegation, but you will still retain
+ the ease of local administration for all name changes.
+ I recommend using a dedicated subdomain for the PTR records, e.g. if
+ your "forward" domain is "HOME.GW.COM" use "REV.HOME.GW.COM" for the
+ PTR records.
+2. Selecting the NS records
+ The NS records for the delegated zone should include all the NS
+ records of the parent zone, in addition to any NS records pointing
+ to the public name servers the delegate may want to use. Having the
+ name servers of the parent zone secondary the delegated zone allows
+ them to have the necessary authoritative data to return the CNAME
+ target in the additional records of a response to a PTR record query
+ (minimizing the number of queries needed to resolve an address).
+ This can be achieved using any zone (i.e. even a subdomain of your
+ "forward" domain), of course. However, having the ISP delegate an
+ IN-ADDR.ARPA zone for your PTR records rather than you delegating a
+ zone to your ISP maintains the logical "owner" and "delegate" roles.
+ If the primary server for the delegated zone is not permanently on
+ the Internet (e.g. a dial-on-demand connection) then you would not
+ want to advertise it in the NS records. It would just be a stealth
+ server which the advertised secondaries poll for updates.
+3. Example delegation
+ To delegate our example zone 0- first look
+ at the NS records of the parent zone 150.80.204.IN-ADDR.ARPA. Let's
+ say they are the following:
+ $ORIGIN 150.80.204.IN-ADDR.ARPA.
+ To delegate to SRV.HOME.GW.COM you would then insert
+ these records in the parent zone data:
+ $ORIGIN 150.80.204.IN-ADDR.ARPA.
+ $GENERATE 0-15 $ IN CNAME $.0-
+ The necessary modifications to /etc/named.conf will be left as an
+ exercise to the reader.
+Kimmo Suominen
+Global Wire Oy