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Revisiting the Use of the IP Protocol Stack in Deep Space: Assessment and Possible Solutions

Document Type Active Internet-Draft (individual)
Authors Marc Blanchet , Christian Huitema , Dean Bogdanović
Last updated 2024-03-04
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Internet Engineering Task Force                              M. Blanchet
Internet-Draft                                                  Viagenie
Intended status: Informational                                C. Huitema
Expires: 5 September 2024                           Private Octopus Inc.
                                                           D. Bogdanovic
                                                           AlefEdge, Inc
                                                            4 March 2024

 Revisiting the Use of the IP Protocol Stack in Deep Space: Assessment
                         and Possible Solutions


   Deep space communications involve long delays (e.g., Earth to Mars is
   4-20 minutes) and intermittent communications, because of orbital
   dynamics.  Up to now, communications have been done on a layer-2
   point to point basis, with sometimes the use of relays, therefore no
   layer-3 networking was possible.  RFC4838 reports an assessment done
   around 25 years ago concluding that the IP protocol stack was not
   suitable for deep space networking.  This result lead to the
   definition of a new protocol stack based on a store-and-forward
   paradigm implemented in the Bundle Protocol(BP).  More recently,
   space agencies are planning to deploy IP networks on celestial
   bodies, such as Moon or Mars, ground, and vicinity.  This document
   revisits the initial assessment of not using IP and provides solution
   paths to use the IP protocol stack, from IP forwarding to transport
   to applications to network management, in deep space communications.

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

   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 5 September 2024.

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Copyright Notice

   Copyright (c) 2024 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 (
   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.

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   3
     1.1.  Requirements Language . . . . . . . . . . . . . . . . . .   5
     1.2.  Document and Discussion location  . . . . . . . . . . . .   5
   2.  IP forwarding . . . . . . . . . . . . . . . . . . . . . . . .   5
   3.  IP Routing  . . . . . . . . . . . . . . . . . . . . . . . . .   6
   4.  QUIC Transport  . . . . . . . . . . . . . . . . . . . . . . .   6
   5.  HTTP  . . . . . . . . . . . . . . . . . . . . . . . . . . . .   8
   6.  COAP  . . . . . . . . . . . . . . . . . . . . . . . . . . . .   9
   7.  UDP Transport . . . . . . . . . . . . . . . . . . . . . . . .  10
   8.  Applications  . . . . . . . . . . . . . . . . . . . . . . . .  10
   9.  Network services  . . . . . . . . . . . . . . . . . . . . . .  10
     9.1.  Domain Name System(DNS) . . . . . . . . . . . . . . . . .  10
     9.2.  Network Management  . . . . . . . . . . . . . . . . . . .  11
     9.3.  Network Operations and Security . . . . . . . . . . . . .  11
     9.4.  Key Management and Distribution . . . . . . . . . . . . .  12
     9.5.  Time  . . . . . . . . . . . . . . . . . . . . . . . . . .  13
   10. Summary . . . . . . . . . . . . . . . . . . . . . . . . . . .  13
   11. IANA Considerations . . . . . . . . . . . . . . . . . . . . .  13
   12. Security Considerations . . . . . . . . . . . . . . . . . . .  13
   13. References  . . . . . . . . . . . . . . . . . . . . . . . . .  13
     13.1.  Normative References . . . . . . . . . . . . . . . . . .  13
     13.2.  Informative References . . . . . . . . . . . . . . . . .  13
   Appendix A.  Additional Considerations  . . . . . . . . . . . . .  18
     A.1.  IP Version  . . . . . . . . . . . . . . . . . . . . . . .  19
     A.2.  IPv6 Addressing . . . . . . . . . . . . . . . . . . . . .  19
     A.3.  IPv6 over Space Links . . . . . . . . . . . . . . . . . .  20
     A.4.  Bundle Protocol and IP  . . . . . . . . . . . . . . . . .  20
   Acknowledgements  . . . . . . . . . . . . . . . . . . . . . . . .  21
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  21

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1.  Introduction

   Deep space communications involve long delays (e.g., Earth to Mars is
   4-20 minutes) and intermittent communications, because of orbital
   dynamics.  Up to now, communications have been done on a layer-2
   point to point basis, with sometimes the use of relays, therefore no
   layer-3 networking was possible.  [RFC4838] reports an assessment
   done around 25 years ago concluding that the IP protocol stack was
   not suitable for deep space networking.  This result lead to the
   definition of a new protocol stack based on a store-and-forward
   paradigm implemented in the Bundle Protocol(BP) [RFC9171] and its
   various components, such as convergence-layer adapters([RFC9174],
   [RFC7122]) and BP Security(BPSEC)[RFC9172].

   More recently, space agencies are planning to deploy IP networks on
   celestial bodies, such as Moon[ioag] or Mars[ioag-mars], ground, and
   vicinity, using layer2 technologies such as WIFI or 5G.

   This document revisits the initial assessment of not using IP and
   provide solution paths to use IP in deep space communications.  IP in
   deep space means running IP over deep space layer-2 links, a reliable
   transport over IP, applications protocols over that transport and
   applying proper routing, security and network management on that IP
   network.  Reusing the whole IP stack in deep space enables the reuse
   of all protocols, tools and software currently used on Internet.
   However, as one might already argue, most of the IP stack can not be
   used as is and therefore requires careful configuration and possibly
   some protocol changes that are discussed in this document.

   The examplary network for this document is where deep space links are
   using IP over CCSDS space links[IPoverCCSDSSpaceLinks] and that on
   and around a celestial body, a connected network is established with
   local network infrastructure and services.

   The keyword Delay-Tolerant Networking (DTN), also expanded to Delay
   and Disruption-Tolerant Networking, has been used to identify the
   problem space and given that up to now, the solution was based on the
   Bundle protocol, DTN was also associated with Bundle protocol.  This
   document tries to solve the DTN problem using the Internet Protocol
   stack.  Therefore, in this document, the DTN keyword is used to name
   the problem space, not the Bundle protocol solution.

   This document covers more topics than what may need to be discussed
   or standardized in IETF, but the intent is to help answer many
   questions raised while looking at the whole problem space, and, in
   this context, provides an non-exhaustive list of topics that needs to
   be addressed.

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   Since Moon is a few light seconds away from Earth, it is possible to
   somewhat configure and run various IP based protocols and
   applications to make it "work".  Mars with a much longer delay is
   more difficult.  Therefore, this document uses Mars as the base
   example, knowing that if it works for Mars, a much harder problem, it
   could be replicated easily for Moon, or for other networks made with
   relays around a celestial body.  This framework shall also work for
   longer delays, such as reaching Jupiter or the whole Solar System
   Internet(SSI), but it is not specifically discussed.  This document
   uses "deep space" extensively in order to differentiate with "space"
   which often includes Earth orbiting communications, which is not
   discussed in this document.

   It should also be noted that DTN and BP were also designed for non-
   space use cases.  While this document focuses on the deep space use
   case, it shall work for the other use cases of BP, but no work or
   discussion on these other use cases is provided in this document.

   Space missions are typically planned many years in advance and are
   long-lived, spanning over many years even decades.  Spacecrafts are
   controlled from Earth and therefore should always be manageable from
   Earth.  Given the remoteness and the difficulty to physically access
   the spacecraft, software upgrades and configuration changes are
   avoided whenever possible.

   As with Bundle protocol, this framework proposes to use IP in deep
   space with the same store-and-forward paradigm.  Therefore, the IP
   layer has to deal with the fact that a destination may not be
   currently reachable and that IP packets should be stored for an
   unusual amount of time, such as minutes or hours or days, in the
   forwarding device waiting for a new link up opportunity.  The
   transport layer should be able to work with long and variable delays,
   including intermittent communications.  The application protocols and
   application themselves should be properly set to wait a longer time
   than on Internet to receive a response to a query.  Finally, all
   network services such as routing, security, naming and network
   management should also be adapted in this new context.  This document
   is structured around these layers.

   In a nutshell, this framework is based on the following main pillars:
   the storage of IP packets in intermediary nodes while the destination
   is unreachable, the use of the QUIC transport[RFC9000] with proper
   configuration, the predominance of using HTTP protocol (over QUIC)
   for applications, the use of IP network services such as routing,
   naming and network management and considerations related to time in
   all levels of the stack.

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1.1.  Requirements Language

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   "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.

1.2.  Document and Discussion location

   The source of this document is located at
   Comments or changes are welcomed as a PR or an issue.

   This subject should be discussed on the mailing

2.  IP forwarding

   In the context of deep space, an IP packet would need to be stored
   temporarily over some possible longer period than typical Internet
   when the next hop is currently unreachable or undefined, for example
   due to orbital dynamics.  Therefore, a new queueing discipline might
   be needed to store packets in this context, that might be implemented
   as a deep queue with active queue management(AQM)[RFC7567].
   Bidirectional Forwarding Detection(BFD)[RFC5880] with large timers
   should be considered.  When the link to the next hop is up, maybe
   minutes or hours later, forwarding tables would be updated and stored
   packets would be forwarded on the link for appropriate destinations.
   This is being discussed in the Time-Variant Routing(TVR) working
   group [TVRWG] and one part is implemented as a YANG model

   The store-and-forward paradigm, either implemented in BP or IP or at
   higher layers, requires proper sizing and provisioning of memory and
   storage for temporarily storing IP packets at each forwarding node
   for the target deployment and usage.

   Store and forward policies shall be defined and implemented to cover
   cases such as when storage is full and new packets are received or
   which priorities should be given to packets when link becomes up.  An
   example is described in [I-D.blanchet-tvr-forwarding].

   Various IP stack kernel buffers used for example for reassembly
   queues need to be properly sized for the target usage.

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   Storing IP packets (or BP bundles) may in fact make the buffer bloat
   issue[buffer-bloat] a much bigger problem if the management of stored
   packets is not properly implemented with the right queueing

3.  IP Routing

   Given the relative static nature of space networks at least for the
   forseeable future, e.g., new nodes or routers are not often added or
   deleted in the network, use of static routes configured based on
   contact plan schedules
   ([I-D.blanchet-tvr-contactplan],[I-D.united-tvr-schedule-yang] may be
   sufficient in the short term.

   If run over space links, IGPs such as OSPFv3 [RFC5340] have time-
   related configurable parameters such as RxmtInterval, InfTransDelay,
   HelloInterval, RouterDeadInterval.  There are 16 bits values in
   seconds, which means a maximum of ~18 hours.  This maximum may be too
   small depending on the contact plan schedule.  Time-Variant
   Routing(TVR) working group [TVRWG] is looking at this problem space.

   Given that it is likely that multiple network operators will be
   present on celestial bodies, it is expected that BGP [RFC4271] would
   be used.

4.  QUIC Transport

   [RFC4838]describes various issues that make the IP protocol suite not
   suitable for space.  One of them is TCP handshake and timers that do
   not work over a 20 minute delay link.  If TLS handshake is added on
   top of TCP, then it is even worse.  In fact, this is similar, but not
   identical because of disruptions, to large bandwidth-delay product
   use cases[RFC1072], because the delay is large, even if the bandwidth
   is somewhat much smaller than on Internet.  In last 25 years,
   transport protocols have evolved a lot.  QUIC ([RFC9000], [RFC9001],
   ...) is a potential transport solution to the space communications
   characteristics, given all its novel features.

   QUIC like most IP transports implements congestion control
   mechanisms, which, based on various metrics such as calculated delays
   or packet loss, pace the rate of sending packets at the source node
   to decrease the perceived congestion in the network.

   Current implementations of QUIC typically set the initial RTT
   estimates in hundreds of milliseconds as it is expected to be a good
   start for connecting establishment on Internet.  However, that value
   is way too low for long delay communications in deep space.  By
   adjusting initial RTT to a proper value in the QUIC stack for the

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   deep space connection, and given that many timers in QUIC are related
   to the RTT, a successful connection can be established.  An initial
   proof of concept[picoquic-poc] with a QUIC implementation[picoquic]
   showed potential use of QUIC in deep space.  Additional timers and
   parameters may need to be adjusted.  Further investigation of QUIC
   use in deep space is needed, especially for congestion control,
   detection and recovering from loss of data.  A document describing
   how to profile a QUIC stack for this use case is being
   written[draft-huitema-quic-in-space].  The possible use of careful
   resume [I-D.ietf-tsvwg-careful-resume] should be considered, as a way
   to dynamically update QUIC client stacks based on a better known RTT
   estimate from the server.

   Establishing a QUIC connections includes discovering the network
   conditions, which typically requires several RTT.  For space
   communications, we need to minimize the impact of the initial delays
   either by keeping connections up for a long time, or if that is not
   possible by using mechanisms like 0RTT or careful resume to
   accelerate the re-discovery of network conditions by the new

   The ability to have multiple streams and applications within a single
   QUIC connection is also very valuable and useful for this use case.
   A ground station may setup the initial QUIC connection with a
   spacecraft and then carry all needed applications and streams over
   that same connection.

   Given that spacecrafts and ground systems are aware of each other and
   are typically managed by the same organization, the trust anchors may
   be preloaded so that each peer already have a trust relationship with
   the other.  This, together with the resume token acquired during a
   previous connection, would enable the use of the 0-RTT QUIC feature
   enabling sending application data on the first packet.  Even more,
   the initial QUIC connection could be established while the spacecraft
   is on the ground, so that while moving in space, the connection only
   needs to be updated with new RTT estimates, either by configuration
   or automatically.  It should be noted that the 0-RTT feature is
   encrypted but vulnerable to replay attacks, which should be
   considered in the missions risk assessment.

   The mandatory ability to have TLS negotiated at the beginning of the
   QUIC connection makes the use of IP layer security (aka IPSec) less
   needed to be deployed, while knowing that IP and transport security
   are different.  Operational complexity in space is very costly and
   brings brittleness of the reliability and therefore, a single layer
   of security, managed at the application transport (aka HTTP-QUIC), is
   very valuable.

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   Session key and certificate lifetime together with certificate
   validation and trust chain anchors need to be carefully configured
   and handled.  This is further discussed in section Section 9.4.

   The store-and-forward paradigm, needed for deep space, may also be
   implemented at the QUIC transport layer instead of the IP layer, by
   architecting a string of QUIC proxies.  Those proxies would need to
   react to the socket error of no connection by storing the data
   payload, until the next opportunity arise.  However, that would
   require that the actual topology of the network be known at each
   proxy and that contact plans also be known at the QUIC proxy layer so
   that the proxy does not try to contact when in fact, no connectivity
   is happening.  There would be no routing updates, so any link change
   from the contact plan would not be used.  However, some messaging
   layer may be put on a network of message relays, connected by QUIC

   QUIC has various applications such as Multiplexed Application
   Substrate over QUIC Encryption(masque)[MASQUEWG] and
   media(moq)[MOQWG] that could also be used in deep space.  Specific
   investigation of these need to be done.

   QUIC may also be implemented without congestion control.  The Bundle
   Protocol stack does not have an end-to-end congestion control
   mechanism and rely on priority queuings set on each link for specific
   bundles.  This priority queuing can be done at the IP forwarding
   layer as discussed previously.  Therefore, implementing a similar
   architecture of Bundle Protocol means that the IP transport may not
   need congestion control.  Moreover, as space links are highly managed
   and carefully allocated and provisionned, end-to-end congestion
   control may not be as needed as on Internet.

   QUIC in deep space has very good promise but requires extensive
   investigation and testing to ensure proper usage and deployment.

5.  HTTP

   HTTP by itself has no notion of time.  An HTTP request and response
   may take minutes or hours to be completed, theoretically.  However,
   current infrastructure and software on Internet have various time-
   related configurations that will not work as is in the deep space

   HTTP headers containing time, such as Cache-Control and Expires
   [RFC9111] need to be set large enough to cover the longest delay so
   that expiration does not happen before the actual data arrives at the
   destination.  As with any HTTP application and content on Internet,
   these headers should be set properly based on the deployment use

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   case, which is ever more important for deep space.  Similarly, when
   continuous content transfer is used, as with 100-Continue [RFC9110],
   proper values for headers should be set.

   HTTP clients and servers typically have default timeouts that shall
   be modified.  For example, curl [curl] has the "-m" option for this
   use case.  Similarly, HTTP server implementations have various
   timeouts configuration variables to be set properly.  Testing with
   HTTP client Curl and HTTP server nginx and an introduced network
   delay of 20 minutes showed that HTTP communications work just fine
   with very basic configuration changes.

   HTTP applications themselves must be developed using an asynchronous
   pattern and if they have timeouts, they should be adjusted

   Internet Web sites are designed with the assumption of hundred of
   milliseconds delay and relatively always connected, where pages
   contain multiple queries to further get resources, media, queries to
   web services and downloading additional code and frameworks.  This
   could work in theory in this context of space, but it will not be
   optimal, as multiple queries will be generated and therefore taking
   multiple RTT before the whole page is received complete.  This issue
   can be mitigated by using various techniques such as Web Assembly
   [wasm] or pre-caching.  Moreover, tt could be possible to have very
   basic HTML pages with zero or very few href and no media content
   unless locally cached to be used.  An example would be a rover on
   Mars presenting an HTTP server with a base and bare HTML page to
   offer basic info on its status (maybe all in text) and some
   additional detailed pages, most likely also in base html text.
   However, it is foreseen that most applications based on QUIC-HTTP
   transport in deep space would be using REST or similar asynchronous
   patterns and not typical web browsing.

   Caching should be used extensively on celestial bodies networks to
   maximize local fetching.  Preemptive caching by pre-populating caches
   with data that shall be used locally on the celestial body network
   shall be done as much as possible to provide better response time on
   the local celestial body network.

   QPACK [RFC9204] should be considered for higher bandwidth efficiency.

6.  COAP

   COAP [RFC7252] is an application transport for use with contrained
   nodes and constrained networks, which fits well with the deep space
   use case.  As such, a COAP profile for deep space use has been
   defined [I-D.gomez-core-coap-space].

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7.  UDP Transport

   This document has a primary focus on HTTP-QUIC-COAP but UDP-based
   protocols and applications are also well suited for deep space, as
   there is no handshake and no notion of congestion control within the
   protocol.  Investigation of which applications and protocols over UDP
   shall be done to provide proper profiles and best practices for deep
   space use.

8.  Applications

   There are a large number of IETF-defined IP-based application
   protocols, as well as non-standard ones.  Some may work as is in a
   deep space environment, some others may require changes in timers or
   else in protocol or in the implementation, and some may not work at
   all.  It would be appropriate to pick the most likely used
   application protocols and assess their usability for this use case.
   It may also be useful to test implementations.  Obviously, the needed
   characteristic of these application protocols is the asynchronous
   paradigm, given long delays and intermittent communications.  One
   outcome of this assessment could be a best practice document on how
   to write applications in such use case.

   It should be noted that if the application is using HTTP as a
   transport, and that guidance on using HTTP as described in Section 5
   is followed, then the HTTP application should work.

9.  Network services

9.1.  Domain Name System(DNS)

   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 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.  The DNSSEC RR TTL values would need to be longer than the
   mission lifetime. [dns-isolated-networks] describes the various ways
   to achieve naming in isolated networks use case, which applies to
   deep space.

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9.2.  Network Management

   NETCONF[RFC6241] and RESTCONF[RFC8040] can be used with proper
   configuration values in implementations to avoid timeouts.  RESTCONF
   with appropriate HTTP config would enable long delayed queries to be
   working.  NETCONF uses TCP which won't work on delayed and
   intermittent communications.  If NETCONF is defined over QUIC, then
   it could be used with proper QUIC profile as discussed in Section 4.
   On the other hand, RESTCONF with proper HTTP profile would just work

   RESTCONF uses various timestamps and HTTP time related headers to
   compare transactions time, so for example to avoid any race in
   configuration changes.  However, there is no notion of timeout in the
   protocol itself, so it should work as is.  Implementations, at the
   RESTCONF level or underneath (HTTP) may have implementation-specific
   timeouts that should be configured properly to handle long delays.

   A network manager should obviously be aware that a RESTCONF
   notification sent by a server that travels over some delayed links or
   networks will arrive later than typical, and such notification may be
   less useful at the time it arrives.  However, this is the reality of
   a delayed and intermittent communications network.

   SSH in its normal interactive mode sends each character in a separate
   packet, which over long delay networks, will not be optimal.  SSH can
   be configured in line mode where packets are sent only when a full
   line is entered.  That mode shall be preferred.  However, SSH like
   NETCONF runs over TCP which will not work.  However, SSH over QUIC
   was proposed[I-D.bider-ssh-quic] which proper QUIC configuration
   might work.

   As a summary, it seems possible that all IP nodes (and even dual-
   stack (BP and IP) nodes) in space can be remotely managed using
   RESTCONF, as well as locally managed.

9.3.  Network Operations and Security

   On Earth, as it is planned today, the space network shall be isolated
   from the current Internet by "air gap", to disable any direct
   communications from Internet to deep space.  Moreover, destination IP
   prefixes filtering shall be used to restrict the traffic to only the
   relevant one for each link.  Note that this shall also be implemented
   in the routing control plane, but additional security might be
   appropriate to further protect the deep space links.

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   Each celestial network edge device shall have firewall rules to
   disable non-useful trafic to go through deep space links.  If
   communications from Mars may only occur to Earth, but not Moon, then
   appropriate filtering based on destination IPv6 prefixes shall be

   Given the air gap on Earth for Internet, there shall be no default
   route advertised in space that could for example point to Earth

   Caching should be used aggressively in all levels of the IP stack in
   this architecture.  For example, DNS servers on remote celestial
   bodies should have all useful names already configured.  HTTP Caches
   should be deployed and preemptively filled with all necessary

   IPsec may be used to provide secure tunnelling or VPN set of
   services.  However, QUIC-TLS may be instead investigated to provide
   the needed security, given that at the transport level, the security
   parameters may be dictated by the applications, therefore ensuring
   security policies from end to end applications, instead of at the
   network level.

   There will likely be multiple "operators" on celestial IP networks.
   Therefore it is likely needed to provide some kind of exchange point
   similar to the Internet Exchange Point(IXP) as we know today on
   Internet.  This would enable local exchange of trafic on the
   celestial body without going through deep space links.  BGP should
   then be considered.

9.4.  Key Management and Distribution

   Protocols or infrastructure using crypto keys and certificates should
   be carefully managed.  Certificates and session keys should have a
   lifetime large enough so that they will still be valid even when
   longer than expected disruptions happen.  For missions, certificate
   lifetimes should be considered based on a mission extended lifetime.
   The whole trust chain for certificate validation, including updates,
   should also be transferred in advance to the appropriate location on
   the celestial body network to avoid invalid verifications because of
   the lack of an intermediate certificate, as one do not want to query
   any parent certificate over space links.  Similarly, Certificate
   Revocation Lists(CRL) real-time fetching [RFC5280] or Online
   Certificate Status Protocol[RFC2560] should be investigated before
   considering their use in this environment.

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9.5.  Time

   Since this framework reuses the IP protocol stack, it inherently
   assumes time coherence between the celestial bodies networks and no
   changes in how protocols are specifying time.  Therefore, as with
   Bundle Protocol suite, it practically assumes UTC-based time being
   available on all celestial bodies, so that time related comparisons
   can be achieved.  The way to accomplish this on the celestial bodies
   networks and in space is out of scope for this document.

10.  Summary

   With proper profiling of protocols, software and operations, and with
   possibly little to no changes in protocols, the use of the IP
   protocol stack in deep space with long delays and intermittent
   communications seems possible and provides an alternative to a Bundle
   protocol based network.  This is now possible to envision because of
   the various advances in the IP stack, specially the QUIC transport,
   compared to the initial assessment done 25 years ago.

11.  IANA Considerations

   This memo includes no request to IANA.

12.  Security Considerations


13.  References

13.1.  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,

   [RFC8174]  Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
              2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
              May 2017, <>.

13.2.  Informative References

   [RFC1072]  Jacobson, V. and R. Braden, "TCP extensions for long-delay
              paths", RFC 1072, DOI 10.17487/RFC1072, October 1988,

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   [RFC2560]  Myers, M., Ankney, R., Malpani, A., Galperin, S., and C.
              Adams, "X.509 Internet Public Key Infrastructure Online
              Certificate Status Protocol - OCSP", RFC 2560,
              DOI 10.17487/RFC2560, June 1999,

   [RFC3633]  Troan, O. and R. Droms, "IPv6 Prefix Options for Dynamic
              Host Configuration Protocol (DHCP) version 6", RFC 3633,
              DOI 10.17487/RFC3633, December 2003,

   [RFC4193]  Hinden, R. and B. Haberman, "Unique Local IPv6 Unicast
              Addresses", RFC 4193, DOI 10.17487/RFC4193, October 2005,

   [RFC4271]  Rekhter, Y., Ed., Li, T., Ed., and S. Hares, Ed., "A
              Border Gateway Protocol 4 (BGP-4)", RFC 4271,
              DOI 10.17487/RFC4271, January 2006,

   [RFC4291]  Hinden, R. and S. Deering, "IP Version 6 Addressing
              Architecture", RFC 4291, DOI 10.17487/RFC4291, February
              2006, <>.

   [RFC4838]  Cerf, V., Burleigh, S., Hooke, A., Torgerson, L., Durst,
              R., Scott, K., Fall, K., and H. Weiss, "Delay-Tolerant
              Networking Architecture", RFC 4838, DOI 10.17487/RFC4838,
              April 2007, <>.

   [RFC4861]  Narten, T., Nordmark, E., Simpson, W., and H. Soliman,
              "Neighbor Discovery for IP version 6 (IPv6)", RFC 4861,
              DOI 10.17487/RFC4861, September 2007,

   [RFC5280]  Cooper, D., Santesson, S., Farrell, S., Boeyen, S.,
              Housley, R., and W. Polk, "Internet X.509 Public Key
              Infrastructure Certificate and Certificate Revocation List
              (CRL) Profile", RFC 5280, DOI 10.17487/RFC5280, May 2008,

   [RFC5340]  Coltun, R., Ferguson, D., Moy, J., and A. Lindem, "OSPF
              for IPv6", RFC 5340, DOI 10.17487/RFC5340, July 2008,

   [RFC5880]  Katz, D. and D. Ward, "Bidirectional Forwarding Detection
              (BFD)", RFC 5880, DOI 10.17487/RFC5880, June 2010,

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   [RFC6241]  Enns, R., Ed., Bjorklund, M., Ed., Schoenwaelder, J., Ed.,
              and A. Bierman, Ed., "Network Configuration Protocol
              (NETCONF)", RFC 6241, DOI 10.17487/RFC6241, June 2011,

   [RFC6724]  Thaler, D., Ed., Draves, R., Matsumoto, A., and T. Chown,
              "Default Address Selection for Internet Protocol Version 6
              (IPv6)", RFC 6724, DOI 10.17487/RFC6724, September 2012,

   [RFC7122]  Kruse, H., Jero, S., and S. Ostermann, "Datagram
              Convergence Layers for the Delay- and Disruption-Tolerant
              Networking (DTN) Bundle Protocol and Licklider
              Transmission Protocol (LTP)", RFC 7122,
              DOI 10.17487/RFC7122, March 2014,

   [RFC7252]  Shelby, Z., Hartke, K., and C. Bormann, "The Constrained
              Application Protocol (CoAP)", RFC 7252,
              DOI 10.17487/RFC7252, June 2014,

   [RFC7567]  Baker, F., Ed. and G. Fairhurst, Ed., "IETF
              Recommendations Regarding Active Queue Management",
              BCP 197, RFC 7567, DOI 10.17487/RFC7567, July 2015,

   [RFC8040]  Bierman, A., Bjorklund, M., and K. Watsen, "RESTCONF
              Protocol", RFC 8040, DOI 10.17487/RFC8040, January 2017,

   [RFC9000]  Iyengar, J., Ed. and M. Thomson, Ed., "QUIC: A UDP-Based
              Multiplexed and Secure Transport", RFC 9000,
              DOI 10.17487/RFC9000, May 2021,

   [RFC9001]  Thomson, M., Ed. and S. Turner, Ed., "Using TLS to Secure
              QUIC", RFC 9001, DOI 10.17487/RFC9001, May 2021,

   [RFC9110]  Fielding, R., Ed., Nottingham, M., Ed., and J. Reschke,
              Ed., "HTTP Semantics", STD 97, RFC 9110,
              DOI 10.17487/RFC9110, June 2022,

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   [RFC9111]  Fielding, R., Ed., Nottingham, M., Ed., and J. Reschke,
              Ed., "HTTP Caching", STD 98, RFC 9111,
              DOI 10.17487/RFC9111, June 2022,

   [RFC9171]  Burleigh, S., Fall, K., and E. Birrane, III, "Bundle
              Protocol Version 7", RFC 9171, DOI 10.17487/RFC9171,
              January 2022, <>.

   [RFC9172]  Birrane, III, E. and K. McKeever, "Bundle Protocol
              Security (BPSec)", RFC 9172, DOI 10.17487/RFC9172, January
              2022, <>.

   [RFC9174]  Sipos, B., Demmer, M., Ott, J., and S. Perreault, "Delay-
              Tolerant Networking TCP Convergence-Layer Protocol Version
              4", RFC 9174, DOI 10.17487/RFC9174, January 2022,

   [RFC9204]  Krasic, C., Bishop, M., and A. Frindell, Ed., "QPACK:
              Field Compression for HTTP/3", RFC 9204,
              DOI 10.17487/RFC9204, June 2022,

              Qu, Y., Lindem, A., Kinzie, E., Fedyk, D., and M.
              Blanchet, "YANG Data Model for Scheduled Attributes", Work
              in Progress, Internet-Draft, draft-united-tvr-schedule-
              yang-01, 3 March 2024,

              Kuhn, N., Emile, S., Fairhurst, G., Secchi, R., and C.
              Huitema, "Convergence of Congestion Control from Retained
              State", Work in Progress, Internet-Draft, draft-ietf-
              tsvwg-careful-resume-07, 16 February 2024,

              Gomez, C. and S. Aguilar, "CoAP in Space", Work in
              Progress, Internet-Draft, draft-gomez-core-coap-space-00,
              19 December 2023, <

              Blanchet, M., Torgerson, J. L., and Y. Qu, "Contact Plan
              Yang Model for Time-Variant Routing of the Bundle

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              Protocol", Work in Progress, Internet-Draft, draft-
              blanchet-tvr-contactplan-01, 7 July 2023,

              Blanchet, M., "Forwarding in the context of Time-Variant
              Routing(TVR)", Work in Progress, Internet-Draft, draft-
              blanchet-tvr-forwarding-00, 13 March 2023,

              bider, D., "QUIC-based UDP Transport for Secure Shell
              (SSH)", Work in Progress, Internet-Draft, draft-bider-ssh-
              quic-09, 2 December 2020,

              Blanchet, M., "Domain Name System in Mostly Isolated
              Networks", Work in Progress, Internet-Draft, draft-
              blanchet-dns-isolated-networks-00, September 2023,

              Consultative Committee on Space Data Systems(CCSDS), "IP
              OVER CCSDS SPACE LINKS, Blue Book 702", September 2012,

              Space Assigned Numbers Authority, "Internet Protocol
              Extension Header",

   [wasm]     World Wide Web Consortium(W3C), "WebAssembly
              Specifications", <>.

   [ioag]     Lunar Communications Architecture Working Group,
              Interagency Operations Advisory Group, "The Future Lunar
              Communications Architecture, Report of the Interagency
              Operations Advisory Group", January 2022,

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              Mars and Beyond Communications Architecture Working Group,
              Interagency Operations Advisory Group, "The Future Mars
              Communications Architecture, Report of the Interagency
              Operations Advisory Group", February 2022,

              Huitema, C., "QUIC to Mars", February 2023,

   [picoquic] Huitema, C., "picoquic",

              Huitema, C. and M. Blanchet, "QUIC in Space",

   [TVRWG]    IETF, "Time-Variant Routing (tvr)",

   [MOQWG]    IETF, "Media Over QUIC (moq)",

   [MASQUEWG] IETF, "Multiplexed Application Substrate over QUIC
              Encryption (masque)",

   [curl]     "Curl", <>.

   [CCSDSWEB] CCSDS, "Consultative Committee for Space Data Systems",

              Gettys, J., "The Blind Men and the Elephant",

Appendix A.  Additional Considerations

   This section lists additional considerations that are important for
   the deployment of IP in deep space, but may not require changes to
   protocols or implementations, as they are more related to network

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A.1.  IP Version

   As discussed in the previous section, space missions are long-lived
   and require full reachability to every spacecraft.  Since IPv4
   address space is consumed, the use of IPv4 address space would rely
   on using Network Address Translation(NAT) in space.  The significant
   consequence is the one-way reachability that NAT creates: as soon as
   there is a NAT in the path from the source to the destination, the
   destination is not be directly reachable.  For example, if a NAT is
   deployed in space, the spacecrafts behind the NAT will not be
   directly reachable from Earth missions operations and network
   management consoles.  If the NAT is on the other side of the
   connections, then spacecrafts will not be able to communicate or send
   notifications to mission operations or network management consoles.
   This is a significant issue if using IPV4 in deep space.

   The Internet has been transitioning from IPv4 to IPv6 to continue its
   expansion and since the missions are long-lived, IPv6 is the only IP
   version that has the appropriate lifetime for the deep space network.

   IPv6 also brings specific features such as IPv6 DHCP prefix
   delegation[RFC3633] that could be used for spacecrafts as mobile
   networks docking into a temporary or more permanent network and
   getting a prefix from the attaching network.

   Finally, running both IPv4 and IPv6 simultaneously, while doable as
   we do on Internet today, brings additional operational challenges
   both in security, such as handling multiple versions of access
   control lists, and network management that one should avoid as much
   as possible in space.

   Therefore, IPv6 is recommended to be the only IP protocol version
   used in space.  Moreover, if there is any required protocol change,
   IPv6 should be the base IP protocol used underneath.

   Most protocols and topics discussed in this document are independent
   of the IP version, but if there are differences, only the IPv6
   version is discussed.

A.2.  IPv6 Addressing

   Space communications infrastructure must avoid at all costs any
   address space collision, since it would prevent any reachability
   between the colliding networks.  For example, if one organization
   creates a network on a celestial body using an address space and
   another organization, or even worse the same organization, creates
   another network anywhere in space using the same address space, those
   two networks will not be able to reach each other, undermining any

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   communications.  NATs can be used between the two but this will just
   further complexify or disable remote network management.

   IPv6 addressing in space should only use non-overlapping address
   space, based on duly allocated IPv6 space assigned to each
   organization, from the public IPv6 address space[RFC4291] managed by
   registries, providing IPv6 network services in space.  IPv6 unique-
   local addressing [RFC4193] can be used within a single domain but
   such traffic should not cross domains using the unique-local
   addressing, and should instead used the global addressing as managed
   by the IPv6 preferred address algorithm [RFC6724].

   Current Regional Internet Registries(RIR) may not have in place the
   appropriate policies for the deep space use case, since these
   policies are aimed towards terrestrial Internet usage, such as
   broadband usage, ISP peering and other considerations.  These
   policies may need to be revised to include deep space usage or
   another organization with proper membership to be put in place to
   allocate and assign IPv6 address space, and possibly Autonomous
   System Numbers, for that specific community and usage.

A.3.  IPv6 over Space Links

   The Consultative Committee for Space Data Systems (CCSDS, [CCSDSWEB]
   is a standard organization for space communications, which membership
   is space agencies and related commercial organizations.  IP packet
   encapsulation into space links is defined in CCSDS 702
   [IPoverCCSDSSpaceLinks] and the codepoint for IPv6 packet
   encapsulation is 87 for space links, as specified in the Space
   Assigned Numbers Registry(SANA) [SANAIPEHeaderRegistry].  However, it
   is unknown if IPv6 has been implemented and tested, given long delays
   and Neighbor Discovery [RFC4861] timers.  An IPv6 over CCSDS Space
   Links specification may need to be defined.

A.4.  Bundle Protocol and IP

   As discussed in Section 1, the Bundle Protocol [RFC9171] has been
   designed to create a store-and-forward networking capability for
   space and other use cases.  This document framework specifies an
   alternate way to accomplish the networking for the same use case by
   reusing as much as possible the IP protocol stack, therefore
   inheriting all the engineering and implementations implemented and
   running daily on Internet.  This re-use also means that
   implementations have been exercised on real traffic orders of
   magnitude more than what has been achieved with Bundle protocol

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   It is possible to mix BP and IP on the same links or networks.
   Therefore, this framework and the BP stack can create independent and
   simultaneous networks or can be mixed.


   This work started by reassessing the use of the whole IP stack in the
   context of deep space.  Soon, QUIC was identified as the key
   technology for this endeavour.  Christian Huitema was very helpful in
   not only confirming the ability to use QUIC but also took the time
   and effort to test and modify its picoquic stack[picoquic] to confirm
   the initial hypothesis[picoquic-poc].  Its involvement and
   confirmation are the key for the launch of this work.  Then, Martin
   Thompson has been also kind to take time to answer initial questions
   on QUIC, further confirming the possibility of using QUIC for deep
   space.  Since then, many individuals have provided significant
   comments and perspectives on this subject.

   This document and its underlying work has been reviewed and discussed
   by many, who have provided valuable feedback and comments, including
   disagreements, and made an overall more solid document.  These people
   are, in no specific order: Geoff Huston, Martin Thompson, Peter
   Ashwood-Smith, Tony Li, George Neville-Neil, Jim Gettys, Nicolas
   Kuhn, Eric Vyncke, Russ Housley, Emile Stephan, Dave Taht, Jean-
   Philippe Dionne.

Authors' Addresses

   Marc Blanchet

   Christian Huitema
   Private Octopus Inc.

   Dean Bogdanovic
   AlefEdge, Inc

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