[RRG] Re: DNS Map: Mapping Resolution Combining Pull/Push Advantages

[Stephane Bortzmeyer <bortzmeyer@nic.fr>]

On Tue, Mar 18, 2008 at 02:40:29PM +0200,
 Christian Vogt <christian.vogt@nomadiclab.com> wrote 
 a message of 45 lines which said:

> If the key is an EID, the query will be for reverse DNS.  Does this
> answer your question?

Yes. So, if you want to know the locator for the EID ABC::1, assuming
someone delegated sixone.arpa, the first Sixone router would query
1.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.c.b.a.0.sixone.arpa. Correct?

> The lookup key is always for a specific host, i.e., either a domain
> name or an address.  The MAP resource records themselves may contain
> aggregated information, however.  They include (in the RDATA field)
> a pair of edge address prefix and transit address prefix -- although
> prefix lengths may be 32 bits (IPv4) or 128 bits (IPv6) to enable
> non-aggregated, per-host mappings.

I am not sure how it could work. Another solution would be to use
aggregation and DNS wildcards. Assuming that ABC::/56 is handled by
the transit address (the address of the ETR in LISP) 1000::1, just add
in the DNS zone file:

*.0.0.0.0.0.0.0.0.0.0.c.b.a.0.sixone.arpa. MAP 1000::1

and that's all, requests for the MAP of ABC::1, ABC::42:1,
ABC::34:56:CAFE:6 would all yield 1000::1.

[Limitation: the resolution is one digit, that is 4 bits. So, you can
handle /56 prefixes but not /55.]

An ANSWER=0 (no MAP records) could mean that the EID is not an EID but
a RLOC.

> Depending on the DNS server implementation, the owner name may be
> filled in dynamically given the lookup key in a DNS query, or MAP
> resource records must be replicated for each possible owner name.

This is also possible.

> The latter can typically be accomplished via macros, which many DNS
> servers provide to generate resource records for a range of owner
> names.

You do not need DNS server support, the zone files can be preprocessed
by the macro system before being giving out to the DNS server.


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