IP in Deep Space: Key Characteristics, Use Cases and Requirements
draft-ietf-tiptop-usecase-01
| Document | Type | Active Internet-Draft (tiptop WG) | |
|---|---|---|---|
| Authors | Marc Blanchet , Wesley Eddy , Marshall Eubanks | ||
| Last updated | 2026-01-21 | ||
| Replaces | draft-many-tiptop-usecase | ||
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draft-ietf-tiptop-usecase-01
Internet Engineering Task Force M. Blanchet
Internet-Draft Viagenie
Intended status: Informational W. Eddy
Expires: 25 July 2026 Aalyria Technologies
M. Eubanks
Space Initiatives Inc
21 January 2026
IP in Deep Space: Key Characteristics, Use Cases and Requirements
draft-ietf-tiptop-usecase-01
Abstract
Deep space communications involve long delays (e.g., Earth to Mars
has one-way delays 4-24 minutes) and intermittent communications,
mainly because of orbital dynamics. The IP protocol stack used on
the Internet is based on the assumptions of shorter delays and mostly
uninterrupted communications. This document describes the key
characteristics, use cases, and requirements for deep space
networking, intended to help when profiling IP protocols in such
environment.
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-
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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 25 July 2026.
Copyright Notice
Copyright (c) 2026 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.
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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 . . . . . . . . . . . . . . . . . . . . . . . . 2
1.1. Limitations of this document . . . . . . . . . . . . . . 3
1.2. Terminology . . . . . . . . . . . . . . . . . . . . . . . 4
1.3. Document and Discussion Locations . . . . . . . . . . . . 4
2. Characteristics . . . . . . . . . . . . . . . . . . . . . . . 5
2.1. Common Aspects . . . . . . . . . . . . . . . . . . . . . 6
2.2. Moon . . . . . . . . . . . . . . . . . . . . . . . . . . 7
2.3. Mars . . . . . . . . . . . . . . . . . . . . . . . . . . 8
2.4. Lagrange Points . . . . . . . . . . . . . . . . . . . . . 10
2.5. Cruising Spacecraft . . . . . . . . . . . . . . . . . . . 10
2.6. Spacecraft Onboard . . . . . . . . . . . . . . . . . . . 10
3. Use Cases . . . . . . . . . . . . . . . . . . . . . . . . . . 10
4. Requirements . . . . . . . . . . . . . . . . . . . . . . . . 13
4.1. Store-and-Forward . . . . . . . . . . . . . . . . . . . . 13
4.2. Time . . . . . . . . . . . . . . . . . . . . . . . . . . 14
4.3. Location . . . . . . . . . . . . . . . . . . . . . . . . 14
4.4. Signaling and Exchanges . . . . . . . . . . . . . . . . . 15
4.5. Bandwidth . . . . . . . . . . . . . . . . . . . . . . . . 15
4.6. Transport . . . . . . . . . . . . . . . . . . . . . . . . 15
4.7. Addressing and Routing . . . . . . . . . . . . . . . . . 15
4.8. Recovery on Reboot . . . . . . . . . . . . . . . . . . . 16
4.9. Energy . . . . . . . . . . . . . . . . . . . . . . . . . 16
5. Security Considerations . . . . . . . . . . . . . . . . . . . 17
6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 17
7. References . . . . . . . . . . . . . . . . . . . . . . . . . 17
7.1. Informative References . . . . . . . . . . . . . . . . . 17
Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . . 21
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 21
1. Introduction
Deep space communications involve long delays (e.g., Earth to Mars is
4-24 minutes one way) and intermittent communications, mainly because
of orbital dynamics. Up to now, communications have typically been
done on a layer-2 point to point basis, in some cases with relays
operating at layer-2 or below. Most missions have operated on their
own, without direct data exchanges between spacecrafts at higher
layers.
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Use of networking technologies, including IP, has become established
within space vehicles that have their own onboard networks. Complex
human exploration and collaborative science missions are driving
increased networking between vehicles. Additionally, there is a
rising need for interoperability between mission end-users and
multiple service providers. As the scale of missions, link
interconnections, and application interactions grows, it will be
increasingly important to support standard IP-based network data
flows.
This document describes the key characteristics and use cases for
networking in deep space. It provides examples taken from the
current communications facilities to reach the Moon and Mars, as well
as future plans. While these examples provide great insight on what
is possible today, the resulting architecture should also consider
future possibilities and farther celestial bodies. For example,
while the number of relays and orbiters around the Moon and Mars is
currently limited, it is expected that their number will increase
significantly, therefore providing improved coverage around those
celestial bodies, resulting in an impact on communications and
networking traffic patterns, intermittence and alternate paths.
Initially the needs considered in this document are to support IP-
based applications in or between private networks, without assumption
of reachability to/from the global Internet. At least initially,
interplanetary IP networks are likely to be protected from the
Internet, and vice-versa the Internet is protected from them (since
they may have unique routing, congestion control, and other
behaviors). However, over time it is possible that connectivity to
the Internet may become available for some mission assets, and
eventually interplanetary networks could become part of the Internet.
This work is a followup of an assessment on the use of the IP
protocol stack in deep space [I-D.many-deepspace-ip-assessment].
1.1. Limitations of this document
Communication in deep space is vastly different than on Earth. This
document does not describe space communication technologies below IP,
but only the information relevant from the IP protocol stack
viewpoint for the purpose of its engineering. More information is
available for the Moon [ioagmoon] and Mars [ioagmars].
Position, Navigation and Timing (PNT) is not directly discussed in
this memo, but is a vital offering from space network service
providers, in addition to data communications. Networking can
support some of the data exchanges that facilitate PNT services.
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Near Earth orbits, such as Low Earth Orbit (LEO), Medium Earth Orbit
(MEO), and Geosynchronous Earth Orbit (GEO) communications and
networking to and from Earth are out of scope for this memo.
However, given the relatively small distance to the Moon, there are
possibilities to use spacecraft around Earth or at Lagrange points as
relays to communicate with lunar assets. In this context, these
possibilities are in scope.
1.2. Terminology
* Deep space: while the ITU definition [deepspacewikipedia] of deep
space is beyond 2 million km, in this document, the Moon and its
environs are included since networking for this regime bears more
similarities to other deep space bodies than to terrestrial and
Earth-orbiting conditions.
* Direct-with-Earth (DWE): communications from/to a spacecraft
directly to/from Earth, without the use of relays.
* Moon, Lunar: refers to Earth's Moon.
* Deep Space Network (DSN): NASA’s international array of giant
radio antennas that supports interplanetary spacecraft missions
[DSN].
* LunaNet Service Providers (LNSP): service providers to the lunar
surface and orbital regions, including private commercial
operators, as defined in the LunaNet Interoperability
Specification [lnis].
* Lagrange Points: special points in the gravitational fields
between bodies (e.g. Earth-Moon, Earth-Sun, etc.), that are
popular mission locations due to stability (i.e. low fuel usage),
visibility for communications or science instruments, or other
reasons. Also known as "libration points".
* Lunar Gateway: a space station orbiting the Moon, that can serve
as a waypoint or other supporting infrastructure for lunar
exploration [Gateway].
1.3. Document and Discussion Locations
The source of this document is located at
https://github.com/marcblanchet/draft-tiptop-usecase. Comments or
changes are welcomed by filing a PR or an issue against that
repository.
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This subject should be discussed on the IETF tiptop working group
mailing list.
2. Characteristics
Compared to Internet on Earth, deep space communications and
networking have multiple challenges, such as:
* Significant and variable delays (e.g. round trips of multiple
seconds, minutes, or hours).
* Frequent and long interruptions of communications, often with no
alternate path. Because of orbital dynamics, a spacecraft may not
be reachable from Earth because it is occluded by a celestial
body. However, spacecraft location and reachability can be
generally precalculated so that the communication windows can be
planned between pairs of spacecraft or between a spacecraft and a
celestial body such as Earth, Moon or Mars.
* Lower bandwidth, sometimes even measured in "bits per second"
rather than typical terrestrial Mbps and Gbps rates.
* One-way / unidirectional links are sometimes used.
* Highly asymmetrical bandwidth and data rates are often present
between uplink (DWE to a spacecraft) and downlink (DWE from a
spacecraft), due to varying transmission power levels, antenna
sizes, and other physical link properties.
* Limited onboard computing resources can lead to simplified or
streamlined protocol implementations.
* Limited energy supply can further reduce contact opportunities and
performance.
Without any changes, a typical Internet application will not work in
this environment, though some Internet stack protocols are more
suitable than others. Among the challenges in this list, the primary
factors impacting Internet stack protocols are delays and
disruptions, discussed in this memo.
This section describes the following cases of mission operating
environments: Moon (surface and orbiting), Mars (surface and
orbiting), Lagrange points, cruising spacecraft, and onboard
spacecraft, starting with some commonality between all cases.
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2.1. Common Aspects
The Consultative Committee for Space Data Systems (CCSDS) is an
organization comprised of many space agencies that has developed
various link-layer protocols used on the links between Earth,
orbiters and surface assets. Examples include Telecommand (TC)
[CCSDS_TC], Telemetry (TM) [CCSDS_TM], Advanced Orbiting Systems
(AOS) [CCSDS_AOS], and Proximity1 (Prox1) [CCSDS_PROX1]]. A newer
Unified Space Data Link Protocol (USLP) [CCSDS_USLP], has been
designed to replace these in the future. A generic encapsulation
mechanism is defined by CCSDS to support networking and other uses
over these link layer protocols, including IPv4, IPv6, and IP header
compression options [IPoverCCSDSSpaceLinks][SANAIPEHeaderRegistry].
IP packets can be transported over any CCSDS link layers.
Surface assets on celestial bodies, such as habitats, rovers,
stations and others may communicate with each other while on the
surface network using Earth terrestrial technologies such as IEEE
802.11 and 3GPP technologies [ioagmoon][ioagmars] using IP, similar
to the Internet, where links are almost always connected and there
are no significant delays. They may also communicate using a relay
orbiter.
Multiple providers, such as the LNSPs for the Moon, will provide
various services including communications and networking.
Orbiters acting as communications relays are already deployed or
planned for both the Moon and Mars. A sufficient number of orbiters
can create a constellation which may provide full coverage of the
celestial body surface [ioagmoon][ioagmars], or at least key regions
(e.g. the lunar south pole). Relaying from one surface asset to
another surface asset through these orbiters may use either CCSDS
link-layers or link-layers similar to LEO constellations on Earth.
Space missions are typically planned many years in advance and are
long-lived, spanning over many years or decades. Spacecraft 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 and backward compatibility is paramount.
Space exploration is more than ever carried by multiple stakeholders.
A mixture of assets operated by government, commercial, and academic/
research organizations from multiple nations are deployed. They will
operate largely independently, but collaboration over time is
expected to meet shared science goals, joint exploration missions,
and mission cross-support needs (e.g. in contingency and emergency
cases).
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While links can be noisy due to weak signals, interference, etc.,
often packet delivery is actually virtually error-free due to the
strong coding available within the link layer. Delivery is generally
in-order. Queuing in modems, gateways, and other systems may be
significant in comparison to typical terrestrial device queues. In
some planetary proximity regimes, CCSDS COP-1 or COP-P link layer
retransmissions may be performed, further improving reliability at
the IP layer (at some expense to delays). Packet losses might be
more common in some specific cases of either very low link margins or
aggressive Adaptive Coding and Modulation (ACM), even though they
might generally be avoided through physical link engineering and
contact planning. See Section 4.2 for requirements related to timers
used for loss detection.
2.2. Moon
There are currently very few orbiters around Moon but there are plans
to establish multiple constellations of them to be used as
communication relays. As few as 5 cooperating orbiters at the right
orbits is sufficient to provide full coverage [ioagmoon], and smaller
sets of orbiters can be targeted to provide full coverage of specific
limited regions such as the far side or the polar regions
[imconstellation]. Until full coverage is accomplished,
interruptions of communications are expected. While Earth ground
stations are able to directly cover assets on the near side of Moon,
use of relays may still be desirable to improve power usage, data
capacity, and spectrum efficiency.
Different types of networking nodes are expected on the lunar
surface, with a wide range of capabilities, from those that have very
limited functionality (similar to IoT devices on Earth), up to more
highly-capable infrastructure hub nodes that provide access for other
surface users (e.g. in a habitat or lander), and in-between cases
such as crewed or uncrewed rovers that may have combinations of
direct-to-Earth, with proximity orbiters, or via local wireless LAN
or cellular capabilities.
The LunaNet Interoperability Specification (LNIS) [lnis] is a
framework including IP networking support for lunar service providers
and users to acheive interoperability.
For human / crewed operations, nearly continuous coverage and data
flows might be expected. However, for other types of network users
(such as science missions), only limited communication opportunities
may be available.
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Some nodes (such as those supporting human missions) may have
multiple/redundant links available simultaneously, but this should
not be expected in general, and even then it is likely to be more for
failover use than for multipath network transport.
Data link operation is scheduled in advance through coordination
between the end-user mission operations centers and LNSPs. The time
windows for operation and data rates are well-known in advance
(typically days or more). Successful link operation generally
requires both directional pointing/tracking (with knowledge of
vehicle locations and motion) of antenna systems, as well as pre-
configuration of modem / signal processing and gateway systems that
require prior coordination on many parameters. Ad hoc or random
access may be available at some later point, but is likely to be rare
for at least proximity and direct-with-Earth links.
Near or on the surface, it is currently expected that the mobile
spacecraft such as rovers or humans will be moving slowly compared to
fast-moving vehicules on terrestrial networks where specific
requirements are needed for handover.
While interoperability and cross support are frequently expected,
there is no assumption in-general that different parties can simply
connect at the link layer or trade packets at the network layer
(either directly or through intermediaries). Network routing and
interconnection is likely to be closely coordinated and limited by
policies established jointly between cooperating organizations. It
is not likely to be directly like the Internet, with BGP, DNS, etc.
generally available to support interdomain operations.
One-way delay from Earth to Moon is around 1.3 seconds.
Capacity is expected to eventually be in the range of hundreds of
Mbps over radio links and Gbps via optical links between Earth and
Moon assets [ioagmoon].
2.3. Mars
There are currently some orbiters around Mars, of which 4 are
actively in use as relays, and 2 active rovers. Multiple missions
are planned[ioagmars] in the coming years. Communications are from
ground stations on Earth, such as the DSN, to Mars orbiters acting as
layer0-1 relays to surface assets such as rovers, and reverse. The
relays do not have notion of frames, and only forward bits at
different frequencies for each segment, a mechanism named "bag of
bits"[ioagmars]. These orbiters can do as "bent-pipe" when the two
segments are active, or by storing the bits as "store-and-forward"
until the next segment becomes available. Since the current set of
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orbiters do not provide full coverage of Mars, the communication
windows are calculated and planned between Earth and each orbiter,
and between each orbiter and each surface asset. Currently, only one
rover can use a relay link at any given time. The MaROS
project[maros] sponsored by the Jet Propulsion Laboratory acts as a
broker to enable missions to enter data about the communications
capabilities such as frequencies, bandwidth, window of communication
time, ... so that rover missions can schedule the available
communications windows for transmitting and receiving. Most orbiters
are used and scheduled in MaROS. One of the Mars orbiters is Mars
Reconnaissance Orbiter(MRO)[mro]. It was launched in 2005 and has a
single 40Mhz processor but over 100G of solid state memory. MaROS
experience over years shows that the current bottleneck is not the
temporary storage of the relays but the bandwidth from Mars surface
assets to Mars orbiter relays. As demonstrated by a
study[marscommstudy] on Mars communication windows, the communication
windows seem to happen at a constant frequency, but the reality shows
that the timing is pretty variable, which means a very large range of
resulting round-trip time (RTT) for communications from Earth to Mars
and back. For example, within 3 months in 2024, the calculated RTT
of the various combinations of orbiters and rovers varied from 30
minutes to 170 hours.
Surface assets are commanded directly from Earth but at a very low
rate. The traffic from the assets to Earth goes through relays.
It is expected that future constellations of Mars orbiters acting as
relays will also have optical inter-satellite links[ioagmars]. The
current orbiters were put in various orbits for the purpose of
science, and usually have a small number of short relay opportunities
per day. However, dedicated relay orbiters could be put at much
higher altitudes to provide much better coverage.
About every two years, a solar conjunction happens for a period of
around 2 weeks, where the Sun is between Earth and Mars, therefore
causing the interruption of communications between Earth and Mars.
One-way delay from Earth to Mars is from 4 to 24 minutes, depending
on the actual relative distance between them.
It is envisioned that optical links between Earth and Mars may
deliver hundreds of Mbps[ioagmars].
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2.4. Lagrange Points
Sun-Earth and Earth-Moon Lagrange points, such as Earth-Moon (EML)-
1,2,4,5 and Earth-Sun (ESL)-1,2, are popular for science mission
objectives and also being considered for communication relays and
therefore potential network forwarders.
Sets of cooperating spacecraft may also be used to increase data
return and streamline operations for science missions co-located at
Lagrange points, by networking locally and sharing a common DWE
"trunk link".
2.5. Cruising Spacecraft
Spacecraft that are cruising towards a deep space destination are
assumed to generally be reached via direct point-to-point links from
Earth using CCSDS link-layers.
2.6. Spacecraft Onboard
Modern spacecraft generally contain multiple computers typically
linked with wired realtime buses or links such as CAN, SpaceWire, RS-
422, and others, but also increasingly using Ethernet or Time-
Triggered Ethernet [tte] (TTE), with IP as the networking layer.
Especially in complex human-crewed vehicles, WiFi is becoming
important, and has been used extensively in the International Space
Station and planned for the Lunar Gateway.
IP networking onboard a spacecraft (or within a habitat) can support
applications within the local network, without experiencing most of
the typical space communications challenges described prior.
Considerations need to be made, however, in order to make sure these
applications do not rely on typical wider infrastructure (e.g. DNS,
NTP, etc.) that may not be externally available in space.
Additionally, some nodes on the network may be mobile/dynamic, such
as astronaut suits and personal electronics, rovers, etc.
3. Use Cases
Multiple countries are developing systems aimed for a sustained lunar
presence combining crewed and robotic missions. The technologies
developed for lunar use are intended to be applied later for Mars as
well, and might equally apply for missions to asteroids and other
deep space bodies. IP has been included in the stack for the
International Deep Space Interoperability Standards [idsis], and the
LunaNet Interoperability Specification [lnis]. There is a general
intention to extend and reuse systems developed for lunar use to
later Mars use.
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Separate space agencies and private companies are deploying lunar
space stations, orbiters, landers, rovers, habitats, crewed mission
elements, and other assets. Due to pervasive use and support of IP
in modern computing systems, it is used onboard many space systems
already, and between co-located systems (e.g. onboard ISS), and
planned to be needed for networking on the Lunar Gateway, in Lunar
3GPP surface networks, and in Lunar habitat LAN and WLAN networks.
As more-and-more IP-enabled assets become deployed in lunar vicinity,
it will increasingly create opportunities to interconnect them. In
fact, internetworking of lunar (and future Mars) systems is becoming
essential, as plans call explicitly for cooperation between mission
elements and communications/navigation system assets operated by
different space agencies and/or private companies acting as service
providers.
There are expected to be several different interoperable LNSPs
offering a variety of relay and/or DWE services, to provide wide
coverage and cross-support opportunities. As more significant
numbers of missions target Mars and other bodies, the same concepts
should apply.
It may be expected that planetary IP networks should over time become
united into larger aggregates, and even into a single interoperable
network (as intended within the LunaNet conception).
It is expected that surface assets (for Moon, Mars, asteroids, etc.)
will communicate with other surface assets on the same body through
typical Earth-based wireless technologies such as WiFi or 4G/5G/6G,
or via a orbiting relays.
Regarding applications, the following is an incomplete list:
* Telecommand: Commanding can take different forms, either
individual commands or batching commands together. Individual
commands sent to a mission/spacecraft from Earth are typically
small (may fit within a single packet in many cases), and should
typically be received reliably and in-order to be processed.
Commands with dependencies or other relations may be grouped
together for transmission and to help assure coherent execution
rather than sent individually. This can resemble small file
transfer, for instance. Commands may be time-sensitive, or have
an "expiration date" after which they are not useful to store/
carry in the network. Required data rates may typically be in
kbps and bursty.
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* Telemetry: Spacecraft stream telemetry data (periodically measured
onboard status, metrics, etc.) to Earth for monitoring and other
purposes. Timely delivery is useful, but storage in the network
is fine, if needed. Required data rates may be approaching the
Mbps range, and often a constant/steady stream of data is
produced.
* On-demand/real-time media(audio, video, ...): when a active path
from the asset to Earth, the asset sends a media feed. The delay
is only the propagation delay.
* Delayed media: the asset sends the media, but it is expected that
there is no active path from the asset to Earth, so data may be
temporarily stored in the network.
* Emergency and Search and Rescue (SAR) messaging: sent from an
asset to one or many other assets (e.g. via broadcast or
multicast) that support emergency operations. Since crew or
mission safety may be at risk, this traffic should be prioritized
over most other types of packets when encountering queuing or
storage within the network. Timely delivery is necessary, but it
should also be delivered reliably.
* Science data: Typically science data may take the form of large
bulk file transfers unicasted from a spacecraft to Earth. In many
cases, storage and large delays in delivery can be tolerated.
File transfer applications such as CCSDS File Delivery Protocol
(CFDP)[CCSDS_CFDP] are typically used, that might be configured to
either operate unidirectionally or may provide reliability through
retransmissions, and require at least small amount of feedback.
Some science applications may also use messaging patterns to
collaborate between different types of instruments in order to
draw attention to events (e.g. gamma ray bursts, etc.) and bring
different types of instruments to bear. These messages may need
to be quickly delivered and/or multicasted.
* Messaging: Many different types of machine-to-machine messaging
need to be supported, including for uses such as (1) providing PNT
data/measurements to feed positioning, orbit determination, and
time transfer or clock calibration, (2) providing space weather
alerts, (3) providing advisory or other network information (e.g.
almanac data such as ephemeris data for relay and other network
elements, scheduled future contacts, or other service management
related messaging). Messages are generally small (though may vary
depending on type) and might be unicast, broadcast, or multicast.
In cases where they are advisory, for instance, they may not need
reliable transport, though often it will be important to provide
timely transmission.
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* Network and Asset management: sending requests and getting answers
from assets about their overall status, status of their
components, energy levels, storage capacities, etc.
4. Requirements
4.1. Store-and-Forward
Until full coverage by orbiter constellations is achieved around a
celestial body, the orbiters and other assets that are facing
intermittent communications should provide store-and-forward
capability. These can be implemented at - layer-1, like the current
Mars orbiters, where frames are not seen ("bag of bits"), at layer-2
doing frame storage or at layer-3 doing packet storage. Storage
higher in the stack enables more versatile, agile and policy-based
routing. A key factor for designing the store and forward capability
of an orbiter is its storage capacity.
Surface assets that are facing intermittent communications also need
the store-and-forward capability.
Mechanisms should be defined to avoid as much as possible storage
full events on a relay. This may include some in-advance signaling
to the network about future full storage event, so that the network
and/or the source can throttle down or reroute packets to avoid that
event.
In the event of full storage, a policy should be determined on which
packets should be dropped, such as the last one in the queue, the
first one in the queue, ones based on policies related to packet or
transport fields like source or destination addresses, traffic
classes, flow ids, etc. , similar to queue management used in
terrestrial networks. These policies are important for
differentiated trafic such as Emergency and Search and Rescue.
Even if calculations can be done based on known orbital dynamics,
events happen that result in missed communication windows. For
example, some communication windows were not used on Mars because a
rover may be still charging and therefore does not have enough energy
to perform communications. Random events can also happen because of
space weather. Therefore, while the window of comms can be
calculated and used, the system should be able to cope with random
long interruption events.
Proper guards should be designed to avoid denial-of-service attacks
by filling storage in the network.
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4.2. Time
Timers are used in transport protocols, application protocols and
applications themselves for various purposes, such as detecting/
presuming packet loss or data lifetime. Timers should be therefore
adjusted and configured based on the expected travel time and RTT
from the source to destination. Given variations and possible
dynamic changes in the network that can cause much longer latency,
appropriate safeguards should be put for timer values.
There are two main challenges that deep space networks pose for use
of timers in loss detection. First, for cases like Mars, the time
needed to infer a loss and request retransmission is much longer than
what protocols are designed for in the Internet, and can be so long
as to preclude retransmission within the same contact window.
Second, for cases where the timing can vary widely, finding
appropriate timeout values and adjusting them automatically may be a
challenge. Mitigating the long propagation delays could be
approached through various techniques such as higher-level erasure
coding (e.g. in application or transport protocols), more aggressive
retransmission policies, or other methods. Mitigating varying delays
can be approached through the use of planning/orchestration systems
to provide guidance on proper values over time, or other methods.
Lifetime is also attached to some data, such as content, security
keys, certificates, tokens, session keys and naming records.
Similarly, the lifetime should be adjusted and configured based on
the characteristics of the applications and expected travel time and
RTT.
Current Internet protocols and applications typically use UTC as
their time reference. There are currently work to define Lunar
Standard Time, also called Coordinated Lunar Time and Mars Standard
Time [lunartime]. Depending on the application and use case, it may
be necessary to adapt the protocol or the application to use another
time reference.
4.3. Location
Some IETF protocols such as [RFC5870][RFC8805] use a Earth coordinate
system such as [WGS84] or address-based reference[RFC8805] for
encoding location. Deep space uses various coordinate systems such
as celestial body references[SANACelestialBodyReference] or orbit-
relative references[SANAOrbitRelativeReference]. Therefore, IETF
protocols carrying location information may need to be updated to
also support space coordinate reference systems. An example of such
space coordinate reference system addition for IETF protocols is in
[RFC9179].
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4.4. Signaling and Exchanges
Given the large latency of space communications, multiple steps of
exchanges or handshakes may still work but are far from optimal and
may never converge. Therefore, applications and protocols should be
adapted to minimize the number of exchanges.
Similarly, applications, protocols or networking stack that depend on
signaling back to the source or to somewhere in the path may arrive
too late for any usefulness, because of the latency. Therefore, any
signaling should be carefully designed based on the expected latency.
4.5. Bandwidth
Given that space communications will always have much lower bandwidth
than what is possible in shorter distances such as on Earth,
optimization of the bandwidth usage is important. This can be
implemented at many levels in the networking stack, starting from
layer-2 to IP header compression to transport and application data
compression.
4.6. Transport
Since IP (and UDP) does not provide reliable transport services, such
as loss, duplicates and reordered recovery, a reliable transport
should be used and configured properly for space delays and
intermittence for applications and protocols requiring it.
Congestion control algorithms may declare congestion based on
heuristics such as when delays are increasing. In that case, sources
pace down to decrease their usage of the bandwidth. However, given
that forwarders in space apply the store-and-forward technique when
link intermittence happen, the congestion seen by the source is not
actually congestion in the typical Internet sense, but deep buffer
usage in forwarders, as a normal and expected operation. Therefore,
congestion control should be adapted or not used because of
intermittence. At least early on, while the networks are small
scale, coordinated resource planning and management may be performed
to avoid creating congestion.
4.7. Addressing and Routing
To minimize routing and forwarding tables, optimal address
aggregation is preferred, and it starts with proper allocation of
addresses.
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The network in deep space, not including the surface networks on
celestial bodies, will grow at a small pace, which does not warrant
complex routing schemes. However, over time, the network will become
sufficiently complex not only because of the number of forwarders but
also because of the intrinsic intermittent and delay communication
patterns, which may warrant more complex routing solutions and
orchestration.
4.8. Recovery on Reboot
On a well-connected and low delay network such as Internet, an
unexpected reboot of an intermediate node or a endpoint is recovered
relatively fast: adjacency can be restored with neighbors for
intermediate nodes, and endpoints can resume or restart their
connections with their peers within short time. On the contrary,
given the intermittence and long delays in deep space, this fast
recovery is unlikely.
For intermediate nodes, storing in permanent memory the contact
schedule or the expected next opportunities for neighbors may help
faster recovery.
For endpoints, applications may keep a state context in permanent
memory, either at the application layer or at the transport layer or
both.
4.9. Energy
Electrical power and energy are constrained in systems operating in
deep space compared to the terrestrial Internet, although with
increasing growth of the Internet of Things (IoT) on Earth, similar
constraints are also present in many terrestrial systems.
Since there are a variety of different types and sizes of deep space
exploration hardware systems, there are different options to generate
power including solar panels or radioisotope thermoelectric
generators (RTGs). Operating off of batteries is common, since
sufficient power is not always able to be generated. In any case,
the available power is limited and when transmitting, a substantial
amount must go to operating amplifiers and other communications
system hardware. Transmissions may be limited to specific times in
order to conserve power and budget it during times when more is not
available to generate (e.g. when operating in lunar "night" on a part
of the moon not exposed to sunlight). Some links and physical layer
protocols operate synchronously and transmit continuously when active
(e.g. using idle frames), while others transmit only data frames and
use "Barker codes" or other burst transmission synchronization
methods.
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The implications of this are that there are a variety of different
modes that networking nodes may be in at any time, and some could
manifest as temporary "disconnections", even if there is antenna
visibility and connectivity would otherwise have been schedulable.
5. Security Considerations
The CCSDS has created a reference document covering general security
threats against space missions, as well as classes of mitigations
[CCSDS-Threats]. This is a useful high-level reference, though it
does not go into depth on networking protocols.
Security protocols and mitigations are most often based on time, such
as keys and certificate lifetimes, tokens lifetime, firewall opened
ports time windows, etc. Keys and certificates have also a lifecycle
where they should be renewed.
Given the delays to act, for example from Earth to a celestial body,
notifications of security issues and mitigation actions will be
delayed, which may increase the impact of security issues such as
denial of service attacks.
Security validation, such as certificate validation, based on on-line
immediate queries to validation databases, such as done with OCSP
[RFC6960], or with a certificate chain will likely take too long if
the validation database is far from the validation querier.
Techniques such as preemptive caching of validation chain and certs
should be investigated.
Certificate lifecycle should be well planned to take into account
delays and intermittence, so that for example certificate renewals
are done sufficiently in advance.
Devices operating in deep space often have limited computational and
memory resources. Key agreement - especially key updates - should be
efficient and scalable. Given the potential lifetime of space
systems and risk of quantum computing to cryptography, this includes
requirements for efficiency and scalability in use of post quantum
cryptography.
6. IANA Considerations
There are no actions for IANA in this document.
7. References
7.1. Informative References
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[RFC5870] Mayrhofer, A. and C. Spanring, "A Uniform Resource
Identifier for Geographic Locations ('geo' URI)",
RFC 5870, DOI 10.17487/RFC5870, June 2010,
<https://www.rfc-editor.org/info/rfc5870>.
[RFC6960] Santesson, S., Myers, M., Ankney, R., Malpani, A.,
Galperin, S., and C. Adams, "X.509 Internet Public Key
Infrastructure Online Certificate Status Protocol - OCSP",
RFC 6960, DOI 10.17487/RFC6960, June 2013,
<https://www.rfc-editor.org/info/rfc6960>.
[RFC8805] Kline, E., Duleba, K., Szamonek, Z., Moser, S., and W.
Kumari, "A Format for Self-Published IP Geolocation
Feeds", RFC 8805, DOI 10.17487/RFC8805, August 2020,
<https://www.rfc-editor.org/info/rfc8805>.
[RFC9179] Hopps, C., "A YANG Grouping for Geographic Locations",
RFC 9179, DOI 10.17487/RFC9179, February 2022,
<https://www.rfc-editor.org/info/rfc9179>.
[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-02, 10 September 2024,
<https://datatracker.ietf.org/doc/html/draft-many-
deepspace-ip-assessment-02>.
[IPoverCCSDSSpaceLinks]
Consultative Committee on Space Data Systems (CCSDS), "IP
OVER CCSDS SPACE LINKS, Blue Book 702", September 2012,
<https://public.ccsds.org/Pubs/702x1b1c2.pdf>.
[SANAIPEHeaderRegistry]
Space Assigned Numbers Authority, "Internet Protocol
Extension Header",
<https://sanaregistry.org/r/ipe_header/>.
[CCSDS_AOS]
Consultative Committee on Space Data Systems (CCSDS), "AOS
Space Data Link Protocol, Blue Book 732.0-B-4", October
2021, <https://public.ccsds.org/Pubs/732x0b4.pdf>.
[CCSDS_TM] Consultative Committee on Space Data Systems (CCSDS), "TM
Space Data Link Protocol, Blue Book 132.0-B-3", October
2021, <https://public.ccsds.org/Pubs/132x0b3.pdf>.
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[CCSDS_TC] Consultative Committee on Space Data Systems (CCSDS), "TC
Space Data Link Protocol, Blue Book 232.0-B-4", October
2021, <https://public.ccsds.org/Pubs/232x0b4e1c1.pdf>.
[CCSDS_PROX1]
Consultative Committee on Space Data Systems (CCSDS),
"Proximity-1 Space Link Protocol—Data Link Layer, Blue
Book 211.0-B-6", July 2020,
<https://public.ccsds.org/Pubs/211x0b6e1.pdf>.
[CCSDS_USLP]
Consultative Committee on Space Data Systems (CCSDS),
"Unified Space Data Link Protocol, Blue Book 732.1-B-2",
October 2021,
<https://public.ccsds.org/Pubs/732x1b2s.pdf>.
[CCSDS_CFDP]
Consultative Committee on Space Data Systems (CCSDS),
"File Delivery Protocol, Blue Book 727.0-B-5", July 2020,
<https://public.ccsds.org/Pubs/727x0b5e1.pdf>.
[SANACelestialBodyReference]
Space Assigned Numbers Authority, "Celestial Body
Reference Frames", May 2023, <https://sanaregistry.org/r/
celestial_body_reference_frames/>.
[SANAOrbitRelativeReference]
Space Assigned Numbers Authority, "Orbit-Relative
Reference Frames", July 2025, <https://sanaregistry.org/r/
orbit_relative_reference_frames/>.
[ioagmoon] Lunar Communications Architecture Working Group,
Interagency Operations Advisory Group, "The Future Lunar
Communications Architecture, Report of the Interagency
Operations Advisory Group", January 2022,
<https://www.ioag.org/Public%20Documents/Lunar%20communica
tions%20architecture%20study%20report%20FINAL%20v1.3.pdf>.
[ioagmars] 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,
<https://www.ioag.org/Public%20Documents/
MBC%20architecture%20report%20final%20version%20PDF.pdf>.
[mro] "Mars Reconnaissance Orbiter",
<https://science.nasa.gov/mission/mars-reconnaissance-
orbiter/>.
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[DSN] "Deep Space Network",
<https://www.nasa.gov/directorates/somd/space-
communications-navigation-program/what-is-the-deep-space-
network/>.
[marscommstudy]
Blanchet, M., "Earth-Mars Communication Windows Usage
Study", October 2024,
<https://deepspaceip.github.io/meetings/ietf121/ietf121-
deepspaceip-mars-communications-study.pdf>.
[idsis] "International Communication System Interoperability
Standards (ICSIS)", September 2020,
<https://internationaldeepspacestandards.com/wp-
content/uploads/2024/02/
communication_reva_final_9-2020.pdf>.
[lnis] "LunaNet Interoperability Specification - Version 5",
February 2025, <https://www.nasa.gov/directorates/somd/
space-communications-navigation-program/lunanet-
interoperability-specification/>.
[deepspacewikipedia]
"Deep space exploration",
<https://en.wikipedia.org/wiki/Deep_space_exploration>.
[maros] Gladden, R., "Mars Relay Operations Service (MaROS): A
Present Service Preparing for the Future", May 2014.
[tte] Wikipedia, "TTEthernet",
<https://en.wikipedia.org/wiki/TTEthernet>.
[lunartime]
NASA, "NASA to Develop Lunar Time Standard for Exploration
Initiatives", September 2024,
<https://www.nasa.gov/general/nasa-to-develop-lunar-time-
standard-for-exploration-initiatives/#:~:text=The%20lunar%
20time%20will%20be,Coordinated%20Universal%20Time%20(UTC)>
.
[imconstellation]
Intuitive Machines, "Intuitive Machines Expands Data
Transmission Services for Lunar and Deep Space Mission",
April 2025, <https://www.intuitivemachines.com/post/
intuitive-machines-expands-data-transmission-services-for-
lunar-and-deep-space-missions>.
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[WGS84] National Imagery and Mapping Agency, "Department of
Defense World Geodetic System 1984, Third Edition, NIMA
TR8350.2", January 2000.
[CCSDS-Threats]
Consultative Committee on Space Data Systems (CCSDS),
"Security Threats Against Space Missions, Green Book
350.1-G-3", February 2022,
<https://ccsds.org/Pubs/350x1g3.pdf>.
[Gateway] Lehnhardt, E. and D. Connell, "The Gateway Program as Part
of NASA's Plans for Human Exploration Beyond Low Earth
Orbit", July 2023,
<https://ntrs.nasa.gov/api/citations/20230014342/
downloads/
IEEE%20-%20Gateway%20Overview%20FINAL%20100223.pdf>.
Acknowledgements
This following people have provided valuable feedback and comments,
in no specific order: Roy Gladden, Padma Pillay-Esnault, Tomek
Mrugalski, Atsushi Tagami, Pascal Thubert, Carles Gomez Montenegro,
Martin Duke, Xisen Tian, Dan York.
Authors' Addresses
Marc Blanchet
Viagenie
Canada
Email: marc.blanchet@viagenie.ca
Wesley Eddy
Aalyria Technologies
United States of America
Email: wes@aalyria.com
Marshall Eubanks
Space Initiatives Inc
United States of America
Email: tme@space-initiatives.com
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