Discussion List for Freenum/ITAD Subscriber Number (ISN) Project

[John Todd <>]

I have a question or two I'd like to pose to the list about storage 
of organization metadata in the DNS:

In creating the Freenum system, there is an underlying need to not 
only provide the linkage of users to NAPTR records, but (probably) 
also the ability for end-user stations or systems to understand 
non-pointer (non-NAPTR) information about the user and the 
organization (ITAD) to which the call is being placed or from which a 
call is received.  There is also a need to search directory 
information for particular organization data, though searching is not 
ideal in the DNS-based method I describe below (though other methods 
(http, ldap?) are planned to be available, they are outside the scope 
of this discussion.)

In the existing Freenum.org zone, the test method in which metadata 
is stored for organizations is in a zone called 
"<itad>.info.freenum.org".  These elements are mapped to X.400-like 
namespace turned into TXT records, like this:

;
; DNS Entry for ITAD 298  Bill Woodcock 
<>
; generated @ 2007-10-03T18:20:57.867979
$ORIGIN freenum.org.
298.info            IN  TXT "o=Packet Clearing House"
                    IN  TXT "street=572 B Ruger Street, Box 29920"
                    IN  TXT "street=The Presidio of San Francisco"
                    IN  TXT "localityName=San Francisco"
                    IN  TXT "stateOrProvince=CA"
                    IN  TXT "postalCode=94129-0920"
                    IN  TXT "c=US"
                    IN  TXT "friendlyCountryName=United States"
                    IN  TXT 
""

  Currently, all of the metadata is returned in a single reply to a 
TXT query (i.e.: "dig TXT 298.info.freenum.org")  This is a problem, 
since all that data has to fit into a single DNS UDP reply.  This is 
very constraining, and quickly will run out of space as DNS replies 
can only typically be 1500 bytes long (and in some cases, replies 
over 512 bytes are rejected by some resolvers/firewalls.)   As the 
size of the metadata list grows, it will soon be the case that it is 
impossible to fit all of the possibly useful identifiers into a 
single reply.

It would be a preference to keep this data centralized in the Freenum 
database instead of allowing it to be delegated to the end 
organizations.  The reason for this is that it seems that the data 
here is fairly static, and is (mostly) also available via the IANA 
pages.  To prevent inadvertent (or malicious) modification of data 
without an audit trail, it seems the best place to leave that data is 
with the "trusted" delegation authority.  I'm interested in hearing 
any potential objections to this centralization for the "base" data 
(much like ARIN/RIPE/etc. already keep some core data about ASNs in a 
single repository.)


Here is my question:
  Would it be more reasonable to create a slightly different layout 
for the metadata, such that it would appear like this in the 
freenum.org zone:

;
; DNS Entry for ITAD 298  Bill Woodcock 
<>
; generated @ 2007-10-03T17:57:29.030819
;
$ORIGIN 298.info.freenum.org.
o                   IN  TXT "Packet Clearing House"
street              IN  TXT "572 B Ruger Street, Box 29920"
street              IN  TXT "The Presidio of San Francisco"
localityName        IN  TXT "San Francisco"
stateorprovince     IN  TXT "CA"
postalcode          IN  TXT "94129-0920"
c                   IN  TXT "US"
friendlyCountryName IN  TXT "United States"
email               IN  TXT 
""

Is this a better method?  In this manner, all that is necessary is to 
make a list of the X.400-style field names available on the 
Freenum.org site, and anyone who wished to write a parser for CDR 
data or screen-pop information could quickly do DNS lookups on this 
ITAD for the particular fieldtype of data they were collecting.  This 
also reduces the maximum size of any one reply down to a single TXT 
record, which will reasonably fit into even a 512 byte reply for any 
forseeably embedded metadata.



Other question:

I've also been considering how this might apply to individual users, 
so that something like this might be suggested as a possible method 
for organizations to "publish" data about individual subscribers 
(note that this would be a suggestion for organizations who operate 
their own nameservers, and would not be published in the freenum.org 
zone, nor would it be mandatory for any records):

; This zone file hypothetically lives on the DNS servers
;  operated by the owner of ITAD 256.  Note: SOA left off
;  for brevity.
;
$ORIGIN 256.freenum.org.
3.0.2.2            NAPTR 100 10 "u" "E2U+sip" 
"!^\\+*([^\\*]*)!sip:\\!"
cn.3.0.2.2         IN  TXT "John Todd"
title.3.0.2.2      IN  TXT "Chief Bottle Washer"
tz.3.0.2.2         IN  TXT "UTC-0800"

Would anyone find this useful if I wrote it up as a specification? 
What data would be useful in here?  Would protocol specific data be 
interesting?  (i.e.:  ua-type.e2u_sip.3.0.2.2.256.freenum.org IN TXT 
"Linksys SPA942")

JT