Satellite Ground Routing Architecture Based on Access Satellite Prediction
draft-hou-rtgwg-satellite-ground-routing-00
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| Document | Type | Active Internet-Draft (individual) | |
|---|---|---|---|
| Authors | Hou Dongxu , Xiao Min | ||
| Last updated | 2024-11-27 | ||
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draft-hou-rtgwg-satellite-ground-routing-00
RTGWG H. Dongxu, Ed.
Internet-Draft X. Min
Intended status: Informational ZTE Corporation
Expires: 31 May 2025 November 2024
Satellite Ground Routing Architecture Based on Access Satellite
Prediction
draft-hou-rtgwg-satellite-ground-routing-00
Abstract
With the development of network technology, the satellite network are
gradually integrating with the terrestrial network. This draft
illustrates a satellite ground routing architecture based on access
satellite prediction to solve the end-to-end communication issue in
the satellite ground integration scenario where the connection
between terrestrial nodes and satellites switches frequently. This
architecture includes registration nodes which are responsible for
maintaining access node information. Each access node preserve
satellite orbit information, performs access satellite prediction,
and generates encapsulation addresses. The access satellite
undertakes data encapsulation, data forwarding, and data
unencapsulation based on encapsulation addresses.
Status of This Memo
This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79.
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This Internet-Draft will expire on 5 May 2025.
Copyright Notice
Copyright (c) 2024 IETF Trust and the persons identified as the
document authors. All rights reserved.
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This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents (https://trustee.ietf.org/
license-info) in effect on the date of publication of this document.
Please review these documents carefully, as they describe your rights
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Requirements Language . . . . . . . . . . . . . . . . . . . . 3
3. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 3
4. Satellite Ground Routing Architecture . . . . . . . . . . . . 4
5. Node Addressing . . . . . . . . . . . . . . . . . . . . . . . 6
6. Encapsulation Address Generation . . . . . . . . . . . . . . 7
7. Extensions and Future Works . . . . . . . . . . . . . . . . . 8
8. Security Considerations . . . . . . . . . . . . . . . . . . . 9
9. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 9
10. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 9
11. References . . . . . . . . . . . . . . . . . . . . . . . . . 9
11.1. Normative References . . . . . . . . . . . . . . . . . . 9
11.2. Informative References . . . . . . . . . . . . . . . . . 9
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 10
1. Introduction
With the development of network technology, the satellite network are
gradually integrating with the terrestrial network. The integration
methods includes BGP-based integration and tunnel-based integration.
The satellite network and the terrestrial network belongs to
different ASs(Autonomous Systems). The routing information between
different ASs are exchanged by BGP. BGP adjacency relationships
between terrestrial nodes and satellites change with connection
variation. If terrestrial routing protocols are directly used in
this scenario, following issues would occurs:
(1) The connection between terrestrial nodes and satellites switch
frequently which causes continuous routing information update.
(2) Sudden connection interruption can't be avoided for the complex
communication environment in the space.
(3) The continuous routing informaiton update further influences the
stability of the terrestrial network.
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Therefore, the tunnel-based integration architecture which isolates
the impact between different networks is a viable approach. In this
architecture, the satellite network is considered as a system which
is independent of the terrestrial network, and doesn't need to
recognize the routing information of the terrestrial network. When
terrestrial nodes communicate across the satellite network, all data
packets need to be encapsulated. The maintenance and acquisition of
packet encapsulation information is the key issue in this method.
Considering this problem, the draft proposes a satellite ground
routing architecture based on access satellite prediction.
The architecture includes registration nodes which are responsible
for maintaining access node information. Each access node preserve
satellite orbit information, performs access satellite prediction,
and generates encapsulation addresses. The access satellite
undertakes data encapsulation, data forwarding, and data
unencapsulation based on encapsulation addresses. Further details
are discussed in subsequent sections.
2. Requirements Language
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
"OPTIONAL" in this document are to be interpreted as described in BCP
14 [RFC2119] [RFC8174] when, and only when, they appear in all
capitals, as shown here.
3. Terminology
* GS: Ground Station
* VLEO: Very Low Earth Orbit with the altitude below 450 km.
* LEO: Low Earth Orbit with the altitude between 180 km and 2000 km.
* MEO: Medium Earth Orbit with the altitude between 2000 km and
35786 km.
* GEO: Geosynchronous Orbit with the altitude 35786 km.
* Intra-satellite links: Links between adjacent satellites in the
same orbit.
* Intra-satellite links: Links between adjacent satellites in the
different orbits.
* SGP4: Simplified Perturbations Models
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* Lon: Longitude
* Lat: Latitude
* BGP: Border Gateway Protocol [RFC4271]
* IGP: Interior Gateway Protocol, examples of IGPs inculde Open
Shortest Path First (OSPF [RFC2328]), Routing Information Protocol
(RIP [RFC2453]), Intermediate System to Intermediate System (IS-IS
[RFC7142]) and Enhanced Interior Gateway Routing Protocol (EIGRP
[RFC7868]).
4. Satellite Ground Routing Architecture
The satellite-ground routing architecture which is based on access
satellite prediction contains three types of nodes, namely the
terrestrial node, the registration node, and the access satellite, as
shown in Figure 1.
.--. .--. .--.
###-| N1 |-### <--> ###-| N2 |-### <--> ###-| N3 |-###
\__/ \__/ ------------ \__/
| | / ---------- \1 |
/|\ /|\ * / 2 \ \ /|\
\___/ ┌---┐ / \ \ O
/ \ |───| * ─+─
Ground | |Registration / \
Station └---┘Node User
Figure 1: Satellite ground routing architecture based on access
satellite prediction
The satellite which communicates with ground nodes at a designated
time is the access satellite. As shown in Figure 1, N1 is the access
satellite of GS(Ground Station). The access satellite needs to
maintain the mapping relationship between all the satellites and the
access network addresses which as shown in Table 1. Considering the
support for different network architectures, the satellite identifier
in the mapping relationship can be IPv4 addresses, IPv6 addresses,
DTN addresses, and etc. Therefore, the address type of satellite
identifiers are not specified in Table 1 and are only represented by
sat1_iden.
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+==================+======================+================+
| Satellite Number | Satellite Identifier | Network Prefix |
+==================+======================+================+
| sat1 | sat1_iden | prefixA |
+------------------+----------------------+----------------+
| sat2 | sat2_iden | prefixB |
+------------------+----------------------+----------------+
| sat3 | sat3_iden | prefixC |
+------------------+----------------------+----------------+
| ...... | ...... | ...... |
+------------------+----------------------+----------------+
Table 1: LEO and its access network prefix with ground nodes
The registration node records the network information of all the
terrestrial nodes accessing the satellite network, as shown in
Table 2. This table describes the mapping relationship between
network nodes or node identifiers and geographic location, e.g.
latitude and longitude.
+==============+=============================+==============+
| Network Node | Node Identifier | Geographical |
| | | Location |
+==============+=============================+==============+
| User | prefix1.area_id1.device_id1 | (lon1,lat1) |
+--------------+-----------------------------+--------------+
| GS | prefix2.area_id2.device_id2 | (lon2,lat2) |
+--------------+-----------------------------+--------------+
| ...... | ...... | ...... |
+--------------+-----------------------------+--------------+
Table 2: Registration information of ground access nodes
The terrestrial node includes ground stations, terminal users, and
etc. When the terrestrial node accesses the satellite network, it
should communicate with the registration node, register its network
information, and obtain network information of other terrestrial
nodes firstly. The registration and information acquisition process
corresponds to "1" and "2" in Figure 1. To build the link with the
registration node, the address of the registration node should be
pre-configured on the terrestrial node. In addition, the pre-
configured information contains the satellite orbit information and
the access network information of different satellites.
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5. Node Addressing
When accessing the satellite network, the terrestrial node
establishes connection with the registration node, and informs its
address as well as location informaiton to the registration node.
Terrestrial nodes switch connections among multiple satellites for
the movement of satellites. The access address of terrestrial nodes
would also change accordingly. Therefore, the address information
registered by terrestrial nodes should meet two requirements:
(1) The address information is the unique identifier of the
terrestrial node.
(2) Based on the address information and the satellite orbit
prediction, the address which is served to connect the remote
terrestrial node and the corresponding access satellite at a
specified time can be determined.
To achieve the above requirements, the address information of
terrestrial nodes is represented by a loopback address or router ID,
and includes two parts of information, namely the geographic area and
the device number within the area. The address format is shown in
Figure 2.
┌--------┬---------┐-----------┐
| Prefix | Area ID | Device ID |
└------─-┴---------┴----─------┘
Figure 2: Address format
Prefix: The prefix part of an address, which can be used to
distinguish node types such as ground stations, end users, and etc.
Area ID: The geographic identifier marks different regions of the
Earth, to achieve the mapping relationship between the location of
the terrestrial node and the Earth's surface regions, as shown in
Figure 3.
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┌---┬---┬---┬---┬---┬---┬---┬---┬---┬---┐
| 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10|
├---+---+---+---+---+---+---+---+---+---┤
| 11| 12| 13| 14| 15| 16| 17| 18| 19| 20|
├---+---+---+---+---+---+---+---+---+---┤
| 21| 22| 23| 24| 25| 26| 27| 28| 29| 30|
├---+---+---+---+---+---+---+---+---+---┤
| 31| 32| 33| 34| 35| 36| 37| 38| 39| 40|
├---+---+---+---+---+---+---+---+---+---┤
| 41| 42| 43| 44| 45| 46| 47| 48| 49| 50|
└---┴---┴---┴---┴---┴---┴---┴---┴---┴---┘
Figure 3: Geographic division
Device ID: The identification information of the terrestrial node,
which is used to distinguish different nodes in the same area.
After registration, the terrestrial node can obtain the existing
registration information in the network from the registration node.
6. Encapsulation Address Generation
Besides address information of the registration node, the satellite
orbit information and the access network information of different
satellites should also be pre-configured on the terrestrial nodes.
The satellite orbit information is used to determine the satellite
ephemeris, that is, to determine which satellite provides services to
the designated Earth area at a specified time. The access network
information of different satellites refers to the network information
used when the satellite is connected to the terrestrial node, and the
format has been explained in the previous section.
Based on the satellite ephemeris, the access satellite of the remote
terrestrial node can be determined at a certain time. Then,
according to the access network of the access satellite and the
address information of the terrestrial node, the access address of
the remote terrestrial node can be calculated at a certain time. A
typical example is as follows.
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The access satellite's access network and the address information of
user is prefixA and prefix1.area_id1 respectively at the time slot
t1. So the corresponding address of user which is applied to
communicate with the access satellite is prefixa.area_id1.device_id1.
As shown in Table 3, with the continuous switching of access
satellites, the access address of the user is constantly changing.
The GS generates and use these access address of destination user for
data packet transmission. The process of GS source address
obtainment is similar with the above description.
+===========+=============================+
| Time Slot | Access Address |
+===========+=============================+
| t0-t1 | prefixA.area_id1.device_id1 |
+-----------+-----------------------------+
| t1-t2 | prefixB.area_id1.device_id1 |
+-----------+-----------------------------+
| t2-t3 | prefixC.area_id1.device_id1 |
+-----------+-----------------------------+
Table 3: Access address of user from t0
to t3
After receiving the data packet from GS, the access satellite of GS
parses the destination address of the packet, obtains the prefix
informaiton, and queries the destination satellite identifier via
this informaiton. Then, the service satellite of GS encapsulates the
original data packet and complete the subsequent transmission using
its own identifier as the source address and the destination
satellite identifier as the destination address.
As soon as the destination satellite receives the data packet, it
unencapsulates the data packet and transfers it to the destination
ground node. The reverse data transmission process of the
destination ground node is similar with the above process, and not
tired in words here.
7. Extensions and Future Works
In the future work, following problems would be taken in mind:
(1) Extension of the current routing protocol to support the
architecture described in this document.
(2) Improvement of the routing algorithm presented in this document
to consider more network metrics and obtain the optimal path
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8. Security Considerations
This document discusses one possible satellite ground routing
architecture. This architecture adds a new mechanism which is access
satellite prediction, but essentially relies on existing routing
protocols. So It has no new security impact.
9. Acknowledgements
TBA
10. IANA Considerations
This document has no IANA actions.
11. References
11.1. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997,
<https://www.rfc-editor.org/info/rfc2119>.
[RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
May 2017, <https://www.rfc-editor.org/info/rfc8174>.
11.2. Informative References
[I-D.ietf-tvr-use-cases]
Birrane, E. J., Kuhn, N., and Y. Qu, "TVR (Time-Variant
Routing) Use Cases", Work in Progress, Internet-Draft,
draft-ietf-tvr-use-cases-00, 15 April 2023,
<https://datatracker.ietf.org/doc/rfc9657>.
[I-D.lhan-satellite-semantic-addressing]
Han, L., Li, R., Retana, A., chenmeiling, and N. Wang,
"Satellite Semantic Addressing for Satellite
Constellation", Work in Progress, Internet-Draft, draft-
lhan-satellite-semantic-addressing-03, 3 March 2023,
<https://datatracker.ietf.org/doc/html/draft-lhan-
satellite-semantic-addressing-03>.
[KUIPER] "Amazon receives FCC approval for project Kuiper satellite
constellation.", <https://tinyurl.com/bs7syjnk>.
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[Large-Scale-LEO-Network-Routing]
"Large Scale LEO Satellite Networks for the Future
Internet: Challenges and Solutions to Addressing and
Routing," Computer Networks and Communications, 1(1),
31-58", <https://ojs.wiserpub.com/index.php/CNC/article/
view/2105>.
[StarLink] "Starlink", <https://en.wikipedia.org/wiki/Starlink>.
[ThreeGPP] "3GPP", <https://www.3gpp.org/>.
Authors' Addresses
Hou Dongxu (editor)
ZTE Corporation
No.50 Software Avenue
Nanjing
Jiangsu, 210012
China
Email: hou.dongxu@zte.com.cn
Xiao Min
ZTE Corporation
No.50 Software Avenue
Nanjing
Jiangsu, 210012
China
Email: xiao.min2@zte.com.cn
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