Network Working Group P. Pfister
Internet-Draft Cisco Systems
Updates: RFC7788 (if approved) T. Lemon
Intended status: Standards Track Nominum, Inc.
Expires: October 22, 2017 April 20, 2017

Special Use Domain ''


This document specifies the behavior that is expected from the Domain Name System with regard to DNS queries for names ending with '', and designates this domain as a special-use domain name. The '' domain replaces '.home' as the default domain used by the Home Networking Control Protocol (HNCP).

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Table of Contents

1. Introduction

Users and devices within a home network require devices and services to be identified by names that are unique within the boundaries of the home network [RFC7368]. The naming mechanism needs to function without configuration from the user. While it may be possible for a name to be delegated by an ISP, home networks must also function in the absence of such a delegation. A default name with a scope limited to each individual home network needs to be used.

The '' domain replaces '.home' which was specified in [RFC7788] as the default domain-name for home networks. '.home' had been selected as the most user-friendly option. However, there are existing uses of '.home' that may be in conflict with this use: evidence indicates that '.home' queries frequently leak out and reach the root name servers [ICANN1] [ICANN2]. Also, ICANN has about a dozen applicants for the '.home' top-level domain name, which creates a significant risk of litigation if it were claimed by the IETF outside of that process. As a result, the use of '.home' has been deprecated; this document updates [RFC7788] to replace '.home' with '', while another document, [I-D.ietf-homenet-redact] deprecates the use of the '.home' TLD.

This document registers the domain '' as a special-use domain name [RFC6761] and specifies the behavior that is expected from the Domain Name System with regard to DNS queries for names whose rightmost non-terminal label is 'homenet'. Queries for names ending with '' are of local significance within the scope of a home network, meaning that identical queries will result in different results from one home network to another. In other words, a name ending in '' is not globally unique.

2. General Guidance

The domain name '' is to be used for naming within a home network. Names ending with '' reference a locally-served zone, the contents of which are unique only to a particular home network, and are not globally unique. Such names refer to nodes and/or services that are located within a home network (e.g., a printer, or a toaster).

DNS queries for names ending with '' are resolved using local resolvers on the homenet. Such queries MUST NOT be recursively forwarded to servers outside the logical boundaries of the home network.

Some service discovery user interfaces that are expected to be used on homenets conceal information such as domain names from end users. However, it is still expected that in some cases, users will need to see, remember, and even type, names ending with ''. It is therefore desirable that users identify the domain and understand that using it expresses the intention to connect to a service that is specific to the home network to which they are connected. Enforcing the fulfillment of this intention is out of scope for this document.

3. Domain Name Reservation Considerations

This section defines the behavior of systems involved in domain name resolution when serving queries for names ending with '' (as per [RFC6761]).

  1. Users can use names ending with '' just as they would use any other domain name. The '' name is chosen to be readily recognized by users as signifying that the name is addressing a service on the homenet to which the user's device is connected.
  2. Applications SHOULD treat domain names ending with '' just like any other FQDN, and MUST NOT make any assumption on the level of additional security implied by its presence.
  3. Name resolution APIs and libraries MUST NOT recognize names that end in '' as special and MUST NOT treat them differently. Name resolution APIs MUST send queries for such names to a recursive DNS server that is configured to be authoritative for the zone appropriate to the home network. One or more IP addresses for recursive DNS servers will usually be supplied to the client through router advertisements or DHCP. If a host is configured to use a resolver other than one that is authoritative for the appropriate zone, the client may be unable to resolve, or may receive incorrect results for, names in sub domains of "".
  4. Unless configured otherwise, recursive resolvers and DNS proxies MUST behave as described in Locally Served Zones ([RFC6303] Section 3). Recursive resolvers that are part of a home network MAY be configured manually or automatically (e.g., for auto-configuration purposes) to act differently, e.g., by querying another name server configured as authoritative for part or all of the '' domain, or proxying the request through a different mechanism.
  5. Only a DNS server that is authoritative for the '.arpa' zone or is configured to be authoritative for '' or a subdomain of '' will ever answer a query about '' In both of these cases, the server should simply answer as configured: no special handling is required.
  6. DNS servers outside a home network should not be configured to be authoritative for
  7. '' is a subdomain of the 'arpa' top-level domain, which is entirely operated by the Internet Architecture Board. As such, no new advice for registrars is required here.

4. Updates to Home Networking Control Protocol

The final paragraph of Homenet Considerations Protocol [RFC7788], section 8, is updated as follows:



5. Security Considerations

A DNS record that is returned as a response to a query ending with '' is expected to have local significance. It is expected to be returned by a server involved in name resolution for the home network the device is connected in. However, such response MUST NOT be considered more trustworthy than would be a similar response for any other DNS query.

Because '' is not globally scoped and cannot be secured using DNSSEC based on the root domain's trust anchor, there is no way to tell, using a standard DNS query, in which home network scope an answer belongs. Consequently, users may experience surprising results with such names when roaming to different home networks. To prevent this from happening, it may be useful for the resolver to identify different home networks on which it has resolved names, but this is out of scope for this document.

In order to enable DNSSEC validation of a particular '', it might make sense to configure a trust anchor for that homenet. How this might be done is out of scope for this document.

6. Delegation of ''

In order to be fully functional, there must be a delegation of '' in the '.arpa' zone. This delegation MUST NOT be signed, MUST NOT include a DS record, and MUST point to one or more black hole servers, for example BLACKHOLE-1.IANA.ORG and BLACKHOLE-2.IANA.ORG. The reason that this delegation must not be signed is that not signing the delegation breaks the DNSSEC chain of trust, which prevents a validating stub resolver from rejecting names published under '' on a homenet name server.

7. IANA Considerations

IANA is requested to record the domain name "" in the Special-Use Domain Names registry [SUDN].

8. Acknowledgments

The authors would like to thank Stuart Cheshire for his prior work on '.home', as well as the homenet chairs: Mark Townsley and Ray Bellis. We would also like to thank Paul Hoffman for providing review and comments on the IANA considerations section.

9. References

9.1. Normative References

[RFC6303] Andrews, M., "Locally Served DNS Zones", BCP 163, RFC 6303, DOI 10.17487/RFC6303, July 2011.
[RFC6761] Cheshire, S. and M. Krochmal, "Special-Use Domain Names", RFC 6761, DOI 10.17487/RFC6761, February 2013.
[I-D.ietf-homenet-redact] Lemon, T., "Redacting .home from HNCP", Internet-Draft draft-ietf-homenet-redact-03, March 2017.

9.2. Informative References

, ", ", "
[RFC1035] Mockapetris, P., "Domain names - implementation and specification", STD 13, RFC 1035, DOI 10.17487/RFC1035, November 1987.
[RFC7368] Chown, T., Arkko, J., Brandt, A., Troan, O. and J. Weil, "IPv6 Home Networking Architecture Principles", RFC 7368, DOI 10.17487/RFC7368, October 2014.
[RFC7788] Stenberg, M., Barth, S. and P. Pfister, Home Networking Control Protocol", RFC 7788, DOI 10.17487/RFC7788, April 2016.
[ICANN1]New gTLD Collision Risk Mitigation", October 2013.
[ICANN2]New gTLD Collision Occurence Management", October 2013.
[SUDN]Special-Use Domain Names Registry", July 2012.

Authors' Addresses

Pierre Pfister Cisco Systems Paris, France EMail:
Ted Lemon Nominum, Inc. 800 Bridge Parkway Redwood City, California 94065 United States of America Phone: +1 650 381 6000 EMail: