DNS Out Of Protocol Signalling

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Table of Contents

1. Introduction

Operators of name servers can benefit from automatically taking action upon certain conditions in the name server software. Some conditions can be monitored from outside the name server software, but for adequate and immediate action, the name server software can signal itself about the condition immediately when it occurs to invoke action by a listener for these signals.¶

An example of such a condition is when all zones, from a set served from an anycasted prefix, are loaded and ready to be served, with the associated automatic actions to only announce a prefix route from the point-of-presence where the name server is running, if all zones from the set are ready to be served, and to withdraw the prefix route if one of the zones cannot be served. This way queries for zones will only reach the point-of-presence if the name server software can answer those queries.¶

Operators of anycasted DNS authoritative services with diverse implementations will benefit from standardizing of the name server signalling, but before coming to a specification for the mechanism, this document will serve to inventorise the already available standardized and non-standardized signalling channels and assess them for usability for out of protocol signalling.¶

Recursive server operators could also benefit from this, having an eventdriven infrastructure - when recursive server is ready to serve, start announcing the service address with BGP. The usual way to do this is by polling the server, and spending resources waiting for this service to come up.¶

2. Terminology and Definitions

The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in BCP 14 [RFC2119][RFC8174] when, and only when, they appear in all capitals, as shown here.¶

3. Conditions to be signalled from within the name server

This section served to collect a list of conditions for which actions outside of the DNS protocol may be interesting. It is by no means meant to be a complete list, but serves to inventorise the requirements for the signalling channel.¶

4. Conditions to be signalled from outside the name server

- Stop the BGP announcement of the prefix

5. Requirements for signalling mechanisms and channels

The following requirements can be distilled from Section 3 and Section 4.¶

6. Existing signalling mechanisms and channels

What follows is a list of existing signalling mechanisms assessed on their suitability based on the requirements outlined in the previous paragraph.¶

7. Security and Privacy Considerations

Signalling MUST be performed in an authenticated and private manner.¶

8. Implementation Status

• Knot DNS has support for D-Bus notifications (See Section 6.3) for significant server and zone events with the "dbus-event" configuration parameter since version 3.1.6 [Knot-DNS-3.1.6]¶
• NSD has a feature branch [NSD-oops-branch] where work is being done on the implementation¶

9. IANA Considerations

This document has no IANA actions¶

10. Acknowledgements

We would like to thank the people of the port53 hackathon in Rotterdam for their contributions. Mainly Doris Hauser, Lars-Johan Liman, Vilhelm Prytz and Henrik Kramselund¶

Appendix A. Implementation Status

Note to the RFC Editor: please remove this entire appendix before publication.¶

Knot currently uses [D-Bus] for this.¶

Appendix B. Change History

Note to the RFC Editor: please remove this entire appendix before publication.¶

• draft-grubto-dnsop-dns-out-of-protocol-signalling-02¶

Updates after discussion during the port53 hackathon in Rotterdam.¶

• draft-grubto-dnsop-dns-out-of-protocol-signalling-00¶

Initial version¶

Authors' Addresses