On Wed, 2003-10-01 at 19:37, Alan DeKok wrote:
information (cost, rates, etc) publicised through DNS.
Faced with the task of synthesyzing disparate proposals into
a coherent whole, one looks for similarities.
I believe that the general technical problem is as follows:
Mapping of a name associated with a domain to a
list of numeric IP addresses, in a way that a
client software function could take arguments
(domain, IP address, name) and return a yes-or-no
answer on the issue of is the IP listed for that
name with that domain.
We also want to avoid adding levels to DNS infrastructure,
which makes any proposal which starts by defining a new DNS
record type a non-starter.
All the various proposals have a mechanism for this feature,
and by deferring the details of what the names are and what
they mean and to what purposes they are defined, we can
Listing in A records is flawed because:
1: without a convention for making the names "special"
some how there is a risk of collision with names already defined
2: an A record can only store seven IP addresses reliably
Issue 1 can be solved by defining a wrapper, such as dashes
before and after the name. "ext" is the name for the purposes
of this document, so the subdomain to query concerning
the list of IP addresses on the "ext" list for example.com
would be -ext-.example.com
Issue 2 can be solved by defining an extended semantics when there
are more than seven IP addresses on the list. The PTR record
syntax of the in-arpa domain can be used here.
It is proposed that when seven or fewer addresses are in a list,
that the addresses are listed in an A record for -ext-.example.com,
and extended listing is allowed but not required.
When there are eight or more records, at least seven MUST be listed in
the A record for -ext-.example.com, and A records are defined for
all listed IP addresses [126.96.36.199] of the form 188.8.131.52.-ext-.example.com
This is called "extended listing."
Extended listing MAY be provided for shorter lists too.
The reply to an extended listing MAY be the address about which the
query was made, but particular extensions may provide alternate
the null address [0.0.0.0] is defined as a negative listing, so that
a listing domain MAY provide a negative listing for all IP addresses
NOT in the list.
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