Stephane Bortzmeyer AFNIC

Immeuble International 78181 Saint-Quentin-en-Yvelines France bortzmeyer@nic.fr

$Date: 2004-03-14 20:59:18 $ 2003 AFNIC This document describes how to set up a small DNS registry using a XML file as the database (both social and technical) and XSLT to produce the zone file.

Every DNS registry will require a database. For large registries, a real DBMS (DataBase Management System) is mandatory. But for small registries, it can be overkill. These small registries (for instance ccTLDs in developing countries) typically use adhoc techniques that have serious drawbacks: Some use only the zone file as a database. Social information is made of comments in that zone file. It prevents any whois-like service to be created. And it does not allow automatic processing of the data (for instance, finding all the domains hold by a given entity). Some use office software like MS-Excel. Since these programs have very poor groupware capabilities, it makes difficult for several people to work on the database. The solution we suggest is to use a XML file for the database: Since it is a text file, groupware tools like CVS will be usable to allow group work. XML is an open format so you do not depend on Microsoft for your data. XML is suitable for automatic processing: we will mostly use XSLT but many other tools are possible. This document has been throughly checked but the ideas presented here have never been actually deployed with a real registry.

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One of the funny things about XML is that you can use several different programming languages to write the schema. You have: DTD (Document Type Definition), a legacy from SGML, widely implemented and recognized. The simplest solution. XML Schemas, a very verbose language. "Schemas" has two meanings, the generic one, which include DTD, for instance and the specific one used in this paragraph. Relax, the least common

When you set up a registry, you have to decide on a schema. Wether it is in SQL or written for XML, this is a policy choice. Here, we will skip the political part and I propose the following schema, written using the DTD language.

With such a schema, you can write a zone file. The zone is a simple text file. You can use any editor you want (although I would recommand Emacs with its psgml package, which simplifies XML edition a lot).

To create a zone file suitable for your nameserver (we will use the syntax of BIND and nsd), a XSL stylesheet can be as simple as: You can apply this stylesheet and automatically get the zone file in the BIND format. Here is an example with libxslt: % xsltproc -o db.tld zone2bind.xslt example-zone.xml But XML allows you much more. Suppose we want to get the information about a contact. we will use the xpath tool, part of Perl XML::XPath moduleSuch a tool is trivial to write with any Xpath library: I have a similar program in Python . xpath allows us to use Xpath queries against our data: % xpath -e '//contact[@handle="SB1"]' ./example-zone.xml Found 1 nodes in ./example-zone.xml: -- NODE -- Bortzmeyer

Abbey Road

London uk 1234 bortzmeyer@hotmail.com ]]> % xpath -e '//contact[city="Saint-Quentin"]' ./example-zone.xml Found 1 nodes in ./example-zone.xml: -- NODE -- Lubrano

Immeuble International

Saint-Quentin fr 1234 lulu@nic.fr ]]>

The whois protocol is defined in . You use it to find out social information about domain registrants, or contacts (technical or administrative). An example of use, with the whois program: % whois -h whois.example.tld linux.tld All rights reserved. Copyright TLD-NIC Domain: linux.tld Registrant name: Torvalds ... We present here a very simple whois server, but which is sufficient for our purposes. It opens the XML file, parse it into a DOM object, then waits for requests. When one arrives, it uses Xpath to query the data.