Domain Name System in Mostly Isolated Networks
draft-many-dnsop-dns-isolated-networks-01

Internet Engineering Task Force                              M. Blanchet
Internet-Draft                                                  Viagenie
Intended status: Informational                           5 November 2023
Expires: 8 May 2024

             Domain Name System in Mostly Isolated Networks
               draft-many-dnsop-dns-isolated-networks-01

Abstract

   This document lists operational methods to enable local DNS name
   resolving on an isolated network, where that target network may have
   intermittent reachability to Internet and/or have very long delays,
   disabling the real-time query and response flow to the authoritative
   name servers on Internet.

Status of This Memo

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   This Internet-Draft will expire on 8 May 2024.

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Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
     1.1.  Requirements Language . . . . . . . . . . . . . . . . . .   3
   2.  Possible Approaches . . . . . . . . . . . . . . . . . . . . .   3
     2.1.  Pre-walk of all needed names  . . . . . . . . . . . . . .   3
     2.2.  Pre-fetch of all zones in the needed name hierarchy . . .   4
     2.3.  Special zone  . . . . . . . . . . . . . . . . . . . . . .   5
   3.  Zone Transfer Coniderations . . . . . . . . . . . . . . . . .   5
   4.  DNSSEC Coniderations  . . . . . . . . . . . . . . . . . . . .   5
   5.  Network Operations Considerations . . . . . . . . . . . . . .   6
   6.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   6
   7.  Security Considerations . . . . . . . . . . . . . . . . . . .   6
   8.  References  . . . . . . . . . . . . . . . . . . . . . . . . .   6
     8.1.  Normative References  . . . . . . . . . . . . . . . . . .   6
     8.2.  Informative References  . . . . . . . . . . . . . . . . .   6
   Acknowledgements  . . . . . . . . . . . . . . . . . . . . . . . .   7
   Author's Address  . . . . . . . . . . . . . . . . . . . . . . . .   7

1.  Introduction

   Deep space communications involve long delays (e.g.  Earth to Mars is
   4-20 minutes) and intermittent communications, because of orbital
   dynamics.  [I-D.many-deepspace-ip-assessment] discusses the use of
   the whole IP stack in this context.  Domain name requests and
   response over long delays generate timeouts and when there is no
   reachability to the DNS server, requests will not be answered.
   Therefore, on celestial bodies IP networks, a local DNS
   infrastructure with all the needed names and values stored locally is
   needed.  Moreover, to keep the same DNS root and the current DNSSEC
   trust chain, all keys necessary for validation should also be stored
   locally.  This document describes the different ways to accomplish
   this.

   While this document uses deep space as the base use case, it applies
   to other "mostly" isolated networks.  Mostly isolated means that most
   of the time the network is isolated, but there are times where it is
   not isolated and then may receive zone transfers or other means to
   populate or update its name caches.  In case of deep space, the
   delays for those transfers is significant and the transport
   mechanisms are more limited, as discussed in
   [I-D.many-deepspace-ip-assessment].

   The requirements and characteristics for this document use case are:

   *  domains under the unique DNS root[RFC2826]

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   *  ability to sometimes reach the mostly isolated name servers to
      update their data cache

   *  most of the time, inability to do live DNS queries to the Internet
      DNS infrastructure

   *  multiple network and DNS operators may exist on the isolated
      network, each managing their own namespace

1.1.  Requirements Language

   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.

2.  Possible Approaches

   This section presents various approaches that should meet the
   requirements set in the previous section.  These approaches use the
   [RFC8806] approach for root zones, but augment it for the whole
   needed name hierarchy.

   All approaches share similar naming infrastructure on the target
   isolated network:

   *  One or more authoritative name server.

   *  One or more resolvers using the above authoritative servers in
      their hints/cache file.

   *  hosts using the above resolvers.

   *  DNSSEC verifying resolvers have the root trust
      anchor[trust-anchor] in their configuration.

2.1.  Pre-walk of all needed names

   If one assumes that all names that will be used on the isolated
   network are known in advance, then queries walking the tree from the
   root down to the final name of all needed names can be done on
   Internet and the responses saved in a file, together with the
   appropriate DNSSEC records (TBD: should we list those: aka RRSIG, DS,
   DNSKEY).  The records should contain values that are relevant to the
   isolated network.  For example, an IP address record such as an A or
   AAAA record should resolve to an IP address relevant and reachable on
   the target isolated network.

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   The resulting file containing all the records is uploaded to the
   authoritative name servers on the isolated network.

   This method somewhat mimics the hosts.txt file used before the DNS
   was created.

   The authoritative name servers should serve the root zone and all
   required domain tree records underneath as found above.

   If a name used on the isolated network by the hosts or applications
   is not in the uploaded file served by the local name servers, then
   the request will leak and will timeout since the request will not
   reach the Internet DNS infrastructure.

   If all needed DNSSEC material is not fully uploaded, then DNSSEC
   validation will fail.

   A method for syncing and updating all the updated records to the
   isolated network should be put in place, at the appropriate
   frequency.  It could be done using zone tranfer mechanism if TCP/IP
   reachability is possible but other file transfer mechanisms may also
   be used.

   Some DNS records have values containing other names, such as the SRV
   and CNAME records.  The referenced names should also be "walked".

   This setup somewhat assumes that there is a single operator for the
   DNS authoritative infrastructure on the target isolated network.

2.2.  Pre-fetch of all zones in the needed name hierarchy

   If one assumes that the name hierarchy is known for all needed names
   used on the isolated network and if the operator of the DNS
   infrastructure on the isolated network has access to all the zones of
   the hierarchy, then these zones are saved.  They may need to be
   modified so that the NS glue records point to the appropriate local
   authoritative name servers.  These zones are then uploaded to the
   authoritative name servers on the isolated network.

   The authoritative name servers should serve the root zone and all
   zones as discussed above.

   This approach have less risk of missing a name since all names under
   the hierarchy are uploaded.  However, if the zones are too big
   compared to the transfer capacity to the isolated network, then this
   solution is not appropriate.  Moreover, it may be possible that most
   of the names in the uploaded zones will not be used, therefore it is
   a possible waste of resources (bandwidth, memory/cpu on server, ...).

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   Therefore, careful consideration on the chosen hierarchy, specially
   the top-level domain, is relevant.  However, it is possible to remove
   all the non-needed recoard from the zones before uploading them to
   the isolated network DNS infrastructure, but then if some names are
   missing in this removal, the same issues from the previous approach
   appear.

   In the context of multiple operators on the target network, each one
   may do this process independently for its own zones, without having
   to rely on another party.

2.3.  Special zone

   Instead of fetching a whole zone containing a lot of non useful
   records, the manager of that zone creates a special version of the
   zone containing only the useful records and sign it.  It is then sent
   to the isolated network DNS infrastructure.  This approach is a
   combination of the previous approaches, but require careful
   management of the two versions of the zone.  In terms of deployment
   and operations, it has the same properties as the zone pre-fetch
   approach.

3.  Zone Transfer Coniderations

   If DNS zone transfer is possible over the link between the Internet
   and the isolated network, then incremental zone transfer (aka IXFR)
   might be advised to minimize the use of the bandwidth and also
   minimize the data merge on the target DNS server.

   If DNS zone transfer is not possible or not optimal, than various
   mechanisms such as FTP, ssh, git, rsync may be used.

4.  DNSSEC Coniderations

   Zones are signed at various frequencies based on the operator
   policies.  If a signature on a record has expired, then DNSSEC
   validation will fail.  Therefore, the frequency of uploading updated
   records should be faster than the frequency of the signing of the
   uploaded zones.

   Similarly, the key lifetimes, including the root zone anchor, should
   be monitored to make sure that new keys are uploaded before the old
   ones expire.

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5.  Network Operations Considerations

   Even with careful management, there is some probability that some
   applications or host on the isolated network will query names that
   were uploaded to the local DNS infrastructure, but refer to services
   or IP addresses that are not reachable from the isolated network.  If
   the isolated network do have intermittent IP connectivity to Internet
   but the link is not appropriate for live queries, such as long delays
   in deep space, costly bandwidth or very small time window of
   reachability, then the network may try to route the packets to the
   Internet.  Therefore, a default route pointing to null or other
   mechanisms to signal unreachability may be appropriate to be setup at
   the edge of the isolated network.

6.  IANA Considerations

   This memo includes no request to IANA.

7.  Security Considerations

   By expanding the use of the same Internet DNS root to space, the
   space IP network naming infrastructure is then secured at the same
   level as on Internet.

8.  References

8.1.  Normative References

   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119,
              DOI 10.17487/RFC2119, March 1997,
              <https://www.rfc-editor.org/info/rfc2119>.

   [RFC8174]  Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
              2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
              May 2017, <https://www.rfc-editor.org/info/rfc8174>.

8.2.  Informative References

   [RFC2826]  IAB, "IAB Technical Comment on the Unique DNS Root",
              RFC 2826, DOI 10.17487/RFC2826, May 2000,
              <https://www.rfc-editor.org/info/rfc2826>.

   [RFC8806]  Kumari, W. and P. Hoffman, "Running a Root Server Local to
              a Resolver", RFC 8806, DOI 10.17487/RFC8806, June 2020,
              <https://www.rfc-editor.org/info/rfc8806>.

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   [trust-anchor]
              IANA, "Trust Anchors and Keys",
              <https://www.iana.org/dnssec/files>.

   [I-D.many-deepspace-ip-assessment]
              Blanchet, M., Huitema, C., and D. Bogdanović, "Revisiting
              the Use of the IP Protocol Stack in Deep Space: Assessment
              and Possible Solutions", Work in Progress, Internet-Draft,
              draft-many-deepspace-ip-assessment-00, 8 September 2023,
              <https://datatracker.ietf.org/doc/html/draft-many-
              deepspace-ip-assessment-00>.

Acknowledgements

   The idea of the pre-walk was suggested by Warren Kumari.  The idea of
   a special zone was suggested by Mark Andrews.  All errors are mine.
   This document and its underlying work has been extensively reviewed
   by many, who have provided valuable feedback and comments, and made
   an overall more solid document.  These people are, in no specific
   order: .

Author's Address

   Marc Blanchet
   Viagenie
   Canada
   Email: marc.blanchet@viagenie.ca

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