Internet DRAFT - draft-many-dnsop-dns-isolated-networks
draft-many-dnsop-dns-isolated-networks
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
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 https://datatracker.ietf.org/drafts/current/.
Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress."
This Internet-Draft will expire on 8 May 2024.
Copyright Notice
Copyright (c) 2023 IETF Trust and the persons identified as the
document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents (https://trustee.ietf.org/
license-info) in effect on the date of publication of this document.
Please review these documents carefully, as they describe your rights
and restrictions with respect to this document. Code Components
extracted from this document must include Revised BSD License text as
described in Section 4.e of the Trust Legal Provisions and are
provided without warranty as described in the Revised BSD License.
Blanchet Expires 8 May 2024 [Page 1]
Internet-Draft DNS in Isolated Networks November 2023
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]
Blanchet Expires 8 May 2024 [Page 2]
Internet-Draft DNS in Isolated Networks November 2023
* 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.
Blanchet Expires 8 May 2024 [Page 3]
Internet-Draft DNS in Isolated Networks November 2023
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, ...).
Blanchet Expires 8 May 2024 [Page 4]
Internet-Draft DNS in Isolated Networks November 2023
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.
Blanchet Expires 8 May 2024 [Page 5]
Internet-Draft DNS in Isolated Networks November 2023
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>.
Blanchet Expires 8 May 2024 [Page 6]
Internet-Draft DNS in Isolated Networks November 2023
[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
Blanchet Expires 8 May 2024 [Page 7]