Updating Parent Zones
draft-andrews-dnsop-update-parent-zones-02

Abstract

DNS UPDATE was developed to allow DNS zones to be updated.

There is a perception that UPDATE can not be used in conjuction with the Registry, Registar, Registrant (RRR) model to update a zone.

This document explains how UPDATE can be used in the RRR model.

Status of This Memo

This Internet-Draft is submitted in full conformance with the provisions of BCP 78 and BCP 79.

Internet-Drafts are working documents of the Internet Engineering Task Force (IETF). Note that other groups may also distribute working documents as Internet-Drafts. The list of current Internet-Drafts is at http://datatracker.ietf.org/drafts/current/.

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This Internet-Draft will expire on May 07, 2014.

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Table of Contents

• 1. Introduction
• 2. Translation
• 3. Authentication
• 4. Direct to Registrar
• 5. Indirect to Registrar
• 6. UPDATE Server Discovery
• 7. Security Considerations
• 8. Normative References
• Author's Address

1. Introduction

UPDATE [RFC2136]is designed to update any zone in the DNS. This includes updating delegating NS records, glue address records and DS record.

While UPDATE is primarily designed to UPDATE a zone directly there in no reason why UPDATE requests cannot be translated to the EPP requests to perform the changes.

This would provide a uniform model to update parent zone regardless of where they are in the DNS heirachy.

2. Translation

The Registrar would host a server that authenticates UPDATE requests received directly or relayed by the Registry using TSIG [RFC2845], then translate the actions in the UPDATE request into EPP transaction requests. The results of those EPP transactions would be relayed to the UPDATE client.

Requests that are not TSIG signed are rejected.

The translating server would handle a restricted subset of UPDATE requests, possibly ignoring the prerequiste section. UPDATE requests would be limited to those supported by EPP.

e.g. Add NS record. Delete all NS records. Add A record. Delete AAAA record. Add DS record. Delete DS record.

The translating server may also override/ignore the TTL in the UPDATE request.

3. Authentication

Authentication would be done using TSIG. TSIG was designed to be used in a environment where requests are relayed.

Authentication can be done down to the <NAME,TYPE> tuple. There exist nameservers that already implement access contols down to this level of granuality based on the presented TSIG.

This would allow nameservers to update their own address records as they get renumbered without being able to update anything else.

This would allow DNSSEC key management software to update DS records without being able to update anything else.

As Registrars do all the authentication and generate the signed responses there is no need for the Registry to have access to the private material using in TSIG. Registrars already handle shared keys in these numbers with their web interfaces.

4. Direct to Registrar

The hardest part of Direct to Registrar is finding where to send the UPDATE request. This would most probably just be advised to the Registrant.

5. Indirect to Registrar

In the indirect model the Registry would host a UPDATE relay server which would examine the first record of the UPDATE section and relay the request to the Registrar of record for the owner name of that record. The response would be relayed back.

The relay can use either TCP or UDP when forwarding UPDATE requests as TSIG supports changes to the DNS id field when a request/response is relayed.

This is consistent with how tools like nsupdate work out where to send a UPDATE request. They look at the ownername of the first record and use it to discover the containing zone.

6. UPDATE Server Discovery

UPDATE server discovery is a issue when the RRR model is in use as the UPDATE may need to be directed through EPP and/or a sent to a Registrar. There are a number of way this could be done.

Adding a underscore infix labels to the zone which contain SRV records at pointing to Registar/Registry servers for each child.

e.g. <child>._update._tcp.<parent> SRV 0 0 53 server.example.tld

The servers pointed could be be a relay server, as described above, or a UDPATE to EPP translating server. A relay server would allow for slower zone growth.

Using underscore infix labels requires no changes to nameservers operated by Registries but does require the zone content to be updated or a separate zone (e.g. _update._tcp.<parent>) be delegated to contain this information.

A level of indirection could be added by using CNAME records to point to a domain operated by the registrar which contains the SRV record. This would allow the registrar to update the SRV records without having to update the zone being served by the registry. The CNAME would be updated on registrar changes. Note the target name the CNAME could also be managed by the registry as a way to consolidate the SRV record management.

As with traditional use of SRV non-support can be signaled with "*._update._tcp SRV 0 0 0 ."

The client can fallback to direct update to parent servers if no SRV record is discovered. This allows the scheme to work outside of the registry, registrar, registant model.

      child._update._tcp.tld CNAME registrar._registrars.tld
      registrar._registrars.tld SRV 0 0 53 server.example.tld
        

Extend UDPATE to return the update server. Currently the Zone section of the UPDATE refers to the zone to be update and is identified by the <QNAME,SOA,QCLASS> tuple. Replacing SOA with one or more of DS, NS, A and AAAA would allow a nameserver to distingish between a traditional UPDATE request and a request to find the UPDATE servers. The tuple would contain the resource to be updated and the reply would contain SRV records pointing to the UPDATE servers. As there would possibly more than one parent the owner records would refer to the parent zone being updated.

One could use a new OPCODE for UPDATE server discovery.

7. Security Considerations

The UPDATE requests are all TSIG signed. This is a proven method for securing UPDATE requests in the DNS.

8. Normative References

Author's Address