| < draft-lai-bmwg-istn-methodology-00.txt | draft-lai-bmwg-istn-methodology-01.txt > | |||
|---|---|---|---|---|
| Benchmarking Methodology Working Group Z. Lai | Benchmarking Methodology Working Group Z. Lai | |||
| Internet-Draft H. Li | Internet-Draft H. Li | |||
| Intended status: Informational Y. Deng | Intended status: Informational Y. Deng | |||
| Expires: 28 April 2022 Q. Wu | Expires: 29 October 2022 Q. Wu | |||
| J. Liu | J. Liu | |||
| Tsinghua University | Tsinghua University | |||
| 25 October 2021 | 27 April 2022 | |||
| Problems and Requirements of Evaluation Methodology for Integrated Space | Problems and Requirements of Evaluation Methodology for Integrated Space | |||
| and Terrestrial Networks | and Terrestrial Networks | |||
| draft-lai-bmwg-istn-methodology-00 | draft-lai-bmwg-istn-methodology-01 | |||
| Abstract | Abstract | |||
| With the rapid evolution of the aerospace industry, many "NewSpace" | With the rapid evolution of the aerospace industry, many "NewSpace" | |||
| upstarts are actively deploying their mega-constellations in low | upstarts are actively deploying their mega-constellations in low | |||
| Earth orbits (LEO) and building integrated space and terrestrial | earth orbits (LEO) and building integrated space and terrestrial | |||
| networks (ISTN), promising to provide pervasive, low-latency, and | networks (ISTN), promising to provide pervasive, low-latency, and | |||
| high-throughput Internet service globally. Due to the high | high-throughput Internet service globally. Due to the high | |||
| manufacturing, launching, and updating cost of LEO mega- | manufacturing, launching, and updating cost of LEO mega- | |||
| constellations, it is expected that ISTNs can be well designed and | constellations, it is expected that ISTNs can be well designed and | |||
| evaluated before the launch of satellites. However, the progress of | evaluated before the launch of satellites. However, the progress of | |||
| designing, assessing, and understanding new network functionalities | designing, assessing, and understanding new network functionalities | |||
| and protocols for futuristic ISTNs faces a substantial obstacle: lack | and protocols for futuristic ISTNs faces a substantial obstacle: lack | |||
| of standardized evaluation methodology with acceptable realism, | of standardized evaluation methodology with acceptable realism (e.g. | |||
| flexibility, and cost that can involve the unique dynamic behaviors | can involve the unique dynamic behaviors of ISTNs), flexibility, and | |||
| of ISTNs. This memo first reviews the unique characteristics of LEO | cost. This memo first reviews the unique characteristics of LEO | |||
| mega-constellations. Further, it analyzes the limitation of existing | mega-constellations. Further, it analyzes the limitation of existing | |||
| network evaluation and analysis methodologies under ISTN | evaluation and analysis methodologies under ISTN environments. | |||
| environments. Finally, it outlines the key requirements of future | Finally, it outlines the key requirements of future evaluation | |||
| evaluation methodology tailored for ISTNs. | methodology tailored for ISTNs. | |||
| Status of This Memo | Status of This Memo | |||
| This Internet-Draft is submitted in full conformance with the | This Internet-Draft is submitted in full conformance with the | |||
| provisions of BCP 78 and BCP 79. | provisions of BCP 78 and BCP 79. | |||
| Internet-Drafts are working documents of the Internet Engineering | Internet-Drafts are working documents of the Internet Engineering | |||
| Task Force (IETF). Note that other groups may also distribute | Task Force (IETF). Note that other groups may also distribute | |||
| working documents as Internet-Drafts. The list of current Internet- | working documents as Internet-Drafts. The list of current Internet- | |||
| Drafts is at https://datatracker.ietf.org/drafts/current/. | Drafts is at https://datatracker.ietf.org/drafts/current/. | |||
| Internet-Drafts are draft documents valid for a maximum of six months | Internet-Drafts are draft documents valid for a maximum of six months | |||
| and may be updated, replaced, or obsoleted by other documents at any | and may be updated, replaced, or obsoleted by other documents at any | |||
| time. It is inappropriate to use Internet-Drafts as reference | time. It is inappropriate to use Internet-Drafts as reference | |||
| material or to cite them other than as "work in progress." | material or to cite them other than as "work in progress." | |||
| This Internet-Draft will expire on 28 April 2022. | This Internet-Draft will expire on 29 October 2022. | |||
| Copyright Notice | Copyright Notice | |||
| Copyright (c) 2021 IETF Trust and the persons identified as the | Copyright (c) 2022 IETF Trust and the persons identified as the | |||
| document authors. All rights reserved. | document authors. All rights reserved. | |||
| This document is subject to BCP 78 and the IETF Trust's Legal | This document is subject to BCP 78 and the IETF Trust's Legal | |||
| Provisions Relating to IETF Documents (https://trustee.ietf.org/ | Provisions Relating to IETF Documents (https://trustee.ietf.org/ | |||
| license-info) in effect on the date of publication of this document. | license-info) in effect on the date of publication of this document. | |||
| Please review these documents carefully, as they describe your rights | Please review these documents carefully, as they describe your rights | |||
| and restrictions with respect to this document. Code Components | and restrictions with respect to this document. Code Components | |||
| extracted from this document must include Simplified BSD License text | extracted from this document must include Revised BSD License text as | |||
| as described in Section 4.e of the Trust Legal Provisions and are | described in Section 4.e of the Trust Legal Provisions and are | |||
| provided without warranty as described in the Simplified BSD License. | provided without warranty as described in the Revised BSD License. | |||
| Table of Contents | Table of Contents | |||
| 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3 | 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3 | |||
| 2. Notation and Terminology . . . . . . . . . . . . . . . . . . 4 | 2. Notation and Terminology . . . . . . . . . . . . . . . . . . 4 | |||
| 3. Quick Primer for Integrated Space and Terrestrial Networks . 5 | 3. Quick Primer for Integrated Space and Terrestrial Networks . 5 | |||
| 3.1. Mega-constellation . . . . . . . . . . . . . . . . . . . 5 | 3.1. Mega-constellation . . . . . . . . . . . . . . . . . . . 5 | |||
| 3.2. Topological Dynamics . . . . . . . . . . . . . . . . . . 6 | 3.2. Topological Dynamics . . . . . . . . . . . . . . . . . . 6 | |||
| 3.3. Long Manufacturing and Deployment Duration . . . . . . . 7 | 3.3. Limited Resources . . . . . . . . . . . . . . . . . . . . 7 | |||
| 3.4. Long Manufacturing and Deployment Duration . . . . . . . 8 | ||||
| 4. Problem Statement: We Need the Right Evaluation | 4. Problem Statement: We Need the Right Evaluation | |||
| Methodology . . . . . . . . . . . . . . . . . . . . . . . 8 | Methodology . . . . . . . . . . . . . . . . . . . . . . . 8 | |||
| 4.1. Live networks and platforms . . . . . . . . . . . . . . . 8 | 4.1. Live networks and platforms . . . . . . . . . . . . . . . 9 | |||
| 4.2. Network Simulators . . . . . . . . . . . . . . . . . . . 9 | 4.2. Network Simulators . . . . . . . . . . . . . . . . . . . 10 | |||
| 4.3. Network Emulators . . . . . . . . . . . . . . . . . . . . 10 | 4.3. Network Emulators . . . . . . . . . . . . . . . . . . . . 11 | |||
| 4.4. Summary . . . . . . . . . . . . . . . . . . . . . . . . . 11 | 4.4. Summary . . . . . . . . . . . . . . . . . . . . . . . . . 12 | |||
| 5. Requirements: New Evaluation Methodology Tailored for | 5. Requirements: New Evaluation Methodology Tailored for | |||
| ISTNs . . . . . . . . . . . . . . . . . . . . . . . . . . 12 | ISTNs . . . . . . . . . . . . . . . . . . . . . . . . . . 12 | |||
| 5.1. Realism . . . . . . . . . . . . . . . . . . . . . . . . . 12 | 5.1. Realism . . . . . . . . . . . . . . . . . . . . . . . . . 13 | |||
| 5.2. Flexibility . . . . . . . . . . . . . . . . . . . . . . . 13 | 5.2. Flexibility . . . . . . . . . . . . . . . . . . . . . . . 13 | |||
| 5.3. Low-cost and Easy-to-use . . . . . . . . . . . . . . . . 13 | 5.3. Low-cost and Easy-to-use . . . . . . . . . . . . . . . . 13 | |||
| 5.4. Cross-domain Dataset Support . . . . . . . . . . . . . . 13 | 5.4. Cross-domain Dataset Support . . . . . . . . . . . . . . 13 | |||
| 6. Conclusion . . . . . . . . . . . . . . . . . . . . . . . . . 14 | 6. Conclusion . . . . . . . . . . . . . . . . . . . . . . . . . 14 | |||
| 7. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 14 | 7. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 14 | |||
| 8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 14 | 8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 14 | |||
| 9. Security Considerations . . . . . . . . . . . . . . . . . . . 14 | 9. Security Considerations . . . . . . . . . . . . . . . . . . . 14 | |||
| 10. References . . . . . . . . . . . . . . . . . . . . . . . . . 14 | 10. References . . . . . . . . . . . . . . . . . . . . . . . . . 14 | |||
| 10.1. Normative References . . . . . . . . . . . . . . . . . . 14 | 10.1. Normative References . . . . . . . . . . . . . . . . . . 14 | |||
| 10.2. Informative References . . . . . . . . . . . . . . . . . 15 | 10.2. Informative References . . . . . . . . . . . . . . . . . 15 | |||
| Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 16 | Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 17 | |||
| 1. Introduction | 1. Introduction | |||
| Integrated Space and Terrestrial Networks (ISTN), combining diverse | Integrated Space and Terrestrial Networks (ISTN), combining diverse | |||
| spacecraft and ground infrastructures, are extending the frontier of | spacecrafts and ground infrastructures, are extending the frontier of | |||
| today's terrestrial network, promising to provide low-latency, high- | today's terrestrial network, promising to provide low-latency, high- | |||
| bandwidth Internet access with broader coverage globally. | bandwidth Internet access with broader coverage globally. | |||
| Low Earth Orbit (LEO) satellites are the key building block for | Low earth orbit (LEO) satellites are the key building block for | |||
| constructing ISTN. Recently, we have witnessed a renaissance in the | constructing ISTNs. Recently, we have witnessed a renaissance in the | |||
| space industry, stimulating an exponential increase in constructing | space industry, stimulating an exponential increase in constructing | |||
| mega-constellations. As compared to their predecessor, cutting-edge | mega-constellations. As compared with their predecessor, cutting- | |||
| satellites can be equipped with high-resolution sensors, space-grade | edge satellites can be equipped with high-resolution sensors, space- | |||
| multi-core processors, high-data-rate communication links, and | grade multi-core processors, high-data-rate communication links, and | |||
| multifunctional space software. | multifunctional space software. | |||
| While ISTNs hold great promise, to completely unleash the network | While ISTNs hold great promise, to completely unleash the network | |||
| potential of emerging ISTN, it still needs to address a series of new | potential of emerging ISTN, it still needs to address a series of new | |||
| research issues. The unique characteristics of LEO satellites (e.g., | technical issues. The unique characteristics of LEO satellites | |||
| high-dynamics), not only impose new challenges at various layers of | (e.g., high-dynamics), not only impose new challenges at various | |||
| the ISTN networking stack but also open the door to many new research | layers of the ISTN networking stack but also open the door to many | |||
| problems. With many unexplored problems facing the "NewSpace" | new technical problems. With many unexplored problems facing the | |||
| industry, it is thus foreseen that in the near future, there will be | "NewSpace" industry, it is thus foreseen that in the near future, | |||
| a surge of new research (e.g. topology, addressing, routing, | there will be a surge of new efforts (e.g. topology, addressing, | |||
| transport, etc.) to rethink and reshape network functionalities and | routing, transport, etc.) to rethink and reshape the networking stack | |||
| protocols in ISTNs. In addition, the cost/ timeline of | in ISTNs. In addition, the cost/timeline of manufacturing, | |||
| manufacturing, launching, operating, and updating satellite | launching, operating, and updating satellite constellations is | |||
| constellations is typically much higher/longer than that in | typically much higher/longer than that in traditional terrestrial | |||
| traditional terrestrial networks. Therefore, it is expected that new | networks. Therefore, it is expected that new network functionalities | |||
| network functionalities and protocols can be well evaluated before | and protocols can be well evaluated before they are launched and | |||
| they are launched and deployed in realistic satellite constellations. | deployed in realistic satellite constellations. | |||
| However, the network community lacks the proper analysis tools and | However, the network community lacks the proper analysis tools and | |||
| evaluation methodologies that can mimic the unique dynamic behavior | evaluation methodologies that can mimic the unique dynamic behavior | |||
| to analyze many of the ISTN challenges that have been highlighted by | to analyze many of the ISTN challenges that have been highlighted by | |||
| prior studies. At high level, existing evaluation methodologies in | prior works. At high level, existing evaluation methodologies in the | |||
| the network community can typically be grouped into three major | network community can typically be grouped into three major | |||
| categories: live networks or platforms, simulation, and emulation. | categories: live networks or platforms, simulation, and emulation. | |||
| However, the feasibility and flexibility of live satellite networks | However, the feasibility and flexibility of live satellite networks | |||
| are technically and economically limited. The abstraction level of | are technically and economically limited. The abstraction level of | |||
| network simulation might be too high to capture low-level system | network simulation could be too high to capture low-level system | |||
| effects. Existing network emulators fail to characterize the high | effects. Existing network emulators fail to characterize the high | |||
| dynamicity of LEO satellites and thus cannot accomplish an | dynamicity of LEO satellites and thus cannot accomplish an | |||
| environment with acceptable fidelity. The community hence needs a | environment with acceptable fidelity. The community hence needs a | |||
| reasonable and standardized evaluation methodology to build proper | reasonable and standardized evaluation methodology to build proper | |||
| experimental environments which can mimic the behavior of ISTNs, | experimental environments which can mimic the behavior of ISTNs, | |||
| supporting the community to deeply understand the problems, and to | supporting the community to deeply understand the problems, and to | |||
| evaluate new functionalities and protocols (e.g. for topology, | evaluate new functionalities and protocols (e.g. for topology, | |||
| addressing, routing, transport, etc.) for ISTNs, before the mega- | addressing, routing, transport, etc.) for ISTNs, before the mega- | |||
| constellation is completely deployed. In this memo, we first review | constellation is completely deployed. In this memo, we first review | |||
| the unique characteristics of emerging LEO mega-constellations and | the unique characteristics of emerging LEO mega-constellations and | |||
| skipping to change at page 5, line 15 ¶ | skipping to change at page 5, line 15 ¶ | |||
| 3. Quick Primer for Integrated Space and Terrestrial Networks | 3. Quick Primer for Integrated Space and Terrestrial Networks | |||
| Emerging mega-constellations with inter-satellite links (ISLs) can | Emerging mega-constellations with inter-satellite links (ISLs) can | |||
| build a satellite network in outer space, and further be integrated | build a satellite network in outer space, and further be integrated | |||
| with terrestrial ground infrastructures to construct an integrated | with terrestrial ground infrastructures to construct an integrated | |||
| space and terrestrial network (ISTN). | space and terrestrial network (ISTN). | |||
| 3.1. Mega-constellation | 3.1. Mega-constellation | |||
| A constellation is a group of satellites working as a system to give | A constellation is a group of satellites working as a system to give | |||
| a coverage of the Earth surface, among which satellites are | a coverage of the earth surface, among which satellites are | |||
| positioned in fixed orbital planes with regular trajectories. LEO | positioned in fixed orbital planes with regular trajectories. LEO | |||
| and MEO satellites often belong to a constellation, because a single | and MEO satellites often belong to a constellation, because a single | |||
| satellite only covers a small area with high angular velocity. Thus, | satellite only covers a small area with high angular velocity. Thus, | |||
| continuous coverage over an area could be maintained by the relay | continuous coverage over an area could be maintained by the relay | |||
| within a constellation, as compared with GEO satellites that only | within a constellation, as compared with GEO satellites that only | |||
| provides a permanent coverage over a target area. Walker Delta | provides a permanent coverage over a target area. Walker Delta | |||
| constellation is the most common formation for constellations. It is | constellation is the most common formation for constellations. It is | |||
| defined as a bunch of circular orbits with a fixed inclination, | defined as a bunch of circular orbits with a fixed inclination, | |||
| satellite number, number of equally spaced planes and the relative | satellite number, number of equally spaced planes and the relative | |||
| spacing between satellites in adjacent planes. The famous Ballard | spacing between satellites in adjacent planes. The famous Ballard | |||
| skipping to change at page 7, line 39 ¶ | skipping to change at page 7, line 39 ¶ | |||
| | Kuiper | 5.0562 | | | Kuiper | 5.0562 | | |||
| +----------+--------------+ | +----------+--------------+ | |||
| | OneWeb | 10.6824 | | | OneWeb | 10.6824 | | |||
| +----------+--------------+ | +----------+--------------+ | |||
| | Telesat | 45.5696 | | | Telesat | 45.5696 | | |||
| +----------+--------------+ | +----------+--------------+ | |||
| Table 2: Space-ground | Table 2: Space-ground | |||
| link churn interval. | link churn interval. | |||
| 3.3. Long Manufacturing and Deployment Duration | 3.3. Limited Resources | |||
| Space resources (e.g. CPU, energy) on satellites are limited, as | ||||
| compared with terrestrial network. Since resource-constrained | ||||
| satellites such as nanosatellites are only able to carry certain | ||||
| sennsing or transferring missions, energy-consuming or complex tasks | ||||
| may not be achievable in these satellites. Such complicated tasks | ||||
| include on-board target identification and instant and continuous | ||||
| disaster monitoring. | ||||
| For example, the CPU frequency of current spaceborne processors (e.g. | ||||
| RAD5545 [RAD5545], RAD750 [RAD750]) is only up to 466MHz per core. | ||||
| More recently, some low energy-consuming commodity processors are | ||||
| used in space to complete certain remote sensing missions under a | ||||
| limited CPU capacity. [raspberry-pi] With a constrained computation | ||||
| ability and limited storage and energy, satellite functions and | ||||
| lifetime are greatly repressed. | ||||
| 3.4. Long Manufacturing and Deployment Duration | ||||
| Different from terrestrial network infrastructures, the timeline of | Different from terrestrial network infrastructures, the timeline of | |||
| manufacturing and deploying satellite networks could be much longer | manufacturing and deploying satellite networks could be much longer | |||
| due to the high cost and complex process during the development and | due to the high cost and complex process during the development and | |||
| launch period. Satellites, as well as the orbit and spectrum they | launch period. Satellites, as well as the orbit and spectrum they | |||
| used, have to be regulated, and launches have to be carefully | used, have to be regulated, and launches have to be carefully | |||
| scheduled (e.g. to avoid the impact of poor weather conditions). In | scheduled (e.g. to avoid the impact of poor weather conditions). In | |||
| addition, the maintenance and update cost of a satellite network is | addition, the maintenance and update cost of a satellite network is | |||
| also typically much higher than that of a terrestrial network. | also typically much higher than that in a terrestrial network. | |||
| For example, a review of 24 Air Force and Navy space vehicle (SV) | For example, a review of 24 Air Force and Navy space vehicle (SV) | |||
| development programs found that on average it took about 7.5 years | development programs found that on average it took about 7.5 years | |||
| from contract start to launch a government satellite. | from contract start to launch a government satellite. | |||
| [Development-Timeline] Commercial satellite programs typically take 2 | [Development-Timeline] Commercial satellite programs typically take 2 | |||
| to 3 years from contract start to launch. [Production-Cycles] | to 3 years from contract start to launch. [Production-Cycles] | |||
| SpaceX's Starlink constellation plan to launch about 42,000 | SpaceX's Starlink constellation plan to launch about 42,000 | |||
| satellites to construct a mega-constellation in outer space. On 15 | satellites to construct a mega-constellation in outer space. On 15 | |||
| October 2019, the United States Federal Communications Commission | October 2019, the United States Federal Communications Commission | |||
| (FCC) submitted filings to the International Telecommunication Union | (FCC) submitted filings to the International Telecommunication Union | |||
| (ITU) on SpaceX's behalf to arrange spectrum for 30,000 additional | (ITU) on SpaceX's behalf to arrange spectrum for 30,000 additional | |||
| Starlink satellites to supplement the 12,000 Starlink satellites | Starlink satellites to supplement the 12,000 Starlink satellites | |||
| already approved by the FCC. As of the date of September 2021, two | already approved by the FCC. As of the date of April 2022, SpaceX | |||
| years after the first launch in May 2019, SpaceX has launched about | has launched about 2,100 Starlink satellites, which is about 5% of | |||
| 1791 Starlink satellites, which is about 4% of the ultimate | the ultimate constellation plan consisting of 42,000 satellites. | |||
| constellation plan consisting of 42,000 satellites. Foreseeably, it | Foreseeably, it may take many years to complete the entire | |||
| may take many years to complete the entire constellation deployment. | constellation deployment. Even the first phase of Starlink which | |||
| Even the first phase of Starlink which consists of about 4400 | consists of about 4400 satellites is not expected to be completed | |||
| satellites is not expected to be completed until 2024. | until 2024. | |||
| 4. Problem Statement: We Need the Right Evaluation Methodology | 4. Problem Statement: We Need the Right Evaluation Methodology | |||
| The unique characteristics of LEO mega-constellations involve new | The unique characteristics of LEO mega-constellations involve new | |||
| challenges on various layers of the networking stack of ISTNs. On | challenges on various layers of the networking stack of ISTNs. On | |||
| one hand, it is foreseen that in the near future, there will be a | one hand, it is foreseen that in the near future, there will be a | |||
| surge of new network functionalities and protocols designed or | surge of new network functionalities and protocols designed or | |||
| optimized for ISTNs. On the other hand, because the cost/timeline of | optimized for ISTNs. On the other hand, because the cost/timeline of | |||
| manufacturing, launching, operating, and updating satellite | manufacturing, launching, operating, and updating satellite | |||
| constellations is typically much higher/longer than that in | constellations is typically much higher/longer than that in | |||
| skipping to change at page 9, line 13 ¶ | skipping to change at page 9, line 29 ¶ | |||
| companies. And for the resource competition, each independent | companies. And for the resource competition, each independent | |||
| experiment needs to completely monopolize a part of the test bed, so | experiment needs to completely monopolize a part of the test bed, so | |||
| the researcher cannot deploy the experiment until being allocated | the researcher cannot deploy the experiment until being allocated | |||
| with enough nodes. PlanetLab [PlanetLab] is truly global ground | with enough nodes. PlanetLab [PlanetLab] is truly global ground | |||
| testbed prototype. Started from 2003, it consists of 1353 nodes at | testbed prototype. Started from 2003, it consists of 1353 nodes at | |||
| 717 sites spanning 48 countries. Together the nodes form a global | 717 sites spanning 48 countries. Together the nodes form a global | |||
| network system to support new design of network services. | network system to support new design of network services. | |||
| The live platforms described above were initially proposed for | The live platforms described above were initially proposed for | |||
| terrestrial networks and they are developed and repaired at the same | terrestrial networks and they are developed and repaired at the same | |||
| time. The key limitation of them in ISTN environment is that they | time. The key limitation of them in an ISTN environment is that they | |||
| are designed for terrestrial network experiments, and do not | are designed for terrestrial network experiments, and do not | |||
| incorporate the realistic characteristic of LEO mega-constellations | incorporate the realistic characteristic of LEO mega-constellations | |||
| to support experiments and evaluations in ISTNs. | to support experiments and evaluations in ISTNs. | |||
| We may search for help from live satellites, but still there is only | We may search for help from live satellites, but still there is only | |||
| limited help. It seems that with the help of live ISTN, researchers | limited help. It seems that with the help of live ISTN, researchers | |||
| are capable to assess, verify and evaluate their ideas and thoughts. | are capable to assess, verify and evaluate their ideas and thoughts. | |||
| Live ISTN can give a real constellation-consistency and stack- | Live ISTN can give a real constellation-consistency and stack- | |||
| consistency testing environment. However, current satellites only | consistency testing environment. However, current satellites only | |||
| provide users a bent-pipe service, which is purely relaying the | provide users a bent-pipe service, which is purely relaying the | |||
| skipping to change at page 9, line 38 ¶ | skipping to change at page 10, line 7 ¶ | |||
| satellites. Besides, the access to satellites is also limited. | satellites. Besides, the access to satellites is also limited. | |||
| Therefore, live networks or platforms for terrestrial networks can | Therefore, live networks or platforms for terrestrial networks can | |||
| give us a large-scale experimental environment but they lack the | give us a large-scale experimental environment but they lack the | |||
| support for ISTN characteristics. On the other hand, live ISTN is | support for ISTN characteristics. On the other hand, live ISTN is | |||
| able to guarantee a real space environment, but it is not that | able to guarantee a real space environment, but it is not that | |||
| affordable and flexible. | affordable and flexible. | |||
| 4.2. Network Simulators | 4.2. Network Simulators | |||
| Simulators are testing methodology tools that enable researchers to | Simulators are tools that enable researchers to reproduce their | |||
| reproduce their testing experiments by simulating a real-world | testing experiments by simulating a real-world process or system over | |||
| process or system over time. Simulators work by using discrete event | time. Simulators work by using discrete event simulation to | |||
| simulation to calculate the interactive states among all the network | calculate the interactive states among all the network entities, | |||
| entities, ranging from switches, routers, nodes, access points, links | ranging from switches, routers, nodes, access points, links and so | |||
| and so on. While working fast and efficiently, the fidelity is only | on. While working fast and efficiently, the fidelity is only brought | |||
| brought by the state variable changes at discrete points. | by the state variable changes at discrete points. | |||
| Such tools like Systems Tool Kit (STK) [Systems-Tool-Kit] and General | Such tools like Systems Tool Kit (STK) [Systems-Tool-Kit] and General | |||
| Mission Analysis Tool (GMAT) [General-Mission-Analysis-Tool] are good | Mission Analysis Tool (GMAT) [General-Mission-Analysis-Tool] are good | |||
| for orbit analysis. STK is a powerful tool to help researchers to | for orbit analysis. STK is a powerful tool to help researchers to | |||
| model the behavior of mission entities in aerospace, | model the behavior of mission entities in aerospace, | |||
| telecommunications and so forth. It also provides visualization and | telecommunications and so forth. It also provides visualization and | |||
| analysis functions. GMAT is a similar tool for space trajectory | analysis functions. GMAT is a similar tool for space trajectory | |||
| optimization and mission modeling. Nevertheless, both tools do not | optimization and mission modeling. Nevertheless, these tools do not | |||
| support networking simulations such as topology and protocol | support networking simulations such as topology and protocol | |||
| simulations. ns-3 [ns-3] goes a step further with support for | simulations. ns-3 [ns-3] goes a step further with support for | |||
| Internet simulation, but on the contrary, it was not designed for | Internet simulation, but on the contrary, it was not designed for | |||
| ISTN and lacks the support for high-dynamics of ISTN. StarPerf | ISTN and lacks the support for high-dynamics of ISTN. StarPerf | |||
| [StarPerf] is a simulator that helps researchers to study network | [StarPerf] is a simulator that helps researchers to study network | |||
| performance under a range of constellation conditions. But still, it | performance under a range of constellation conditions. But still, it | |||
| lacks the ability to support interactive network traffic simulation | lacks the ability to support interactive network traffic simulation | |||
| and system codes in the systems. | and system codes in the systems. | |||
| Overall, while flexible and low-cost, the realism of simulators is | Overall, while flexible and low-cost, the realism of simulators is | |||
| not content enough, because they are too abstract to realize the low- | not content enough, because they are difficult to describe the low- | |||
| level characteristics. In other words, simulators are being too | level characteristics. In other words, simulators are being too | |||
| object-oriented to involve additional overhead in the actual | object-oriented to involve additional overhead in the actual | |||
| execution of programs. Besides, when accessing the network | execution of programs. Besides, when accessing the network | |||
| performance, a number of recent emerging algorithms for congestion | performance, a number of recent emerging algorithms for congestion | |||
| control, reliable transmission or even protocols are not supported, | control, reliable transmission or even protocols are not supported, | |||
| for example ns-3 [ns-3] only supports basic congestion control like | for example ns-3 [ns-3] only supports basic congestion control like | |||
| Reno [RFC6582] and so forth, so the need to work with some new | Reno [RFC6582] and so forth, so the need to work with some new | |||
| algorithms cannot be satisfied and the research to discover new | algorithms cannot be satisfied and the research to discover new | |||
| mechanisms, such as new routing algorithms and re-transmission | mechanisms, such as new routing algorithms and re-transmission | |||
| schemes, is extensively prohibited. Another problem of simulators, | schemes, is extensively prohibited. Another problem of simulators, | |||
| such as ns-3 [ns-3], is that it difficult to trace or understand the | such as ns-3 [ns-3], is that it difficult to trace or understand the | |||
| previous codes, without appropriate documentations. Simulators | previous codes, without appropriate documentations. Simulators | |||
| usually face the additional compatibility problem, which means they | usually face the additional compatibility problem, which means they | |||
| is not portable with other systems, or they do not support kernel | are not portable with other systems, or they do not support kernel | |||
| codes. Since there are multiple simulators developed by different | codes. Since there are multiple simulators developed by different | |||
| group of users, sometimes users are required to be familiar with the | group of users, sometimes users are required to be familiar with the | |||
| writing language, scripting style and modelling technique. So, the | writing language, scripting style and modelling technique. | |||
| Tool Command Language might be difficult to understand and write. | ||||
| 4.3. Network Emulators | 4.3. Network Emulators | |||
| Emulators are another kind of paradigm for testing methodology tool | Emulators are another kind of paradigm for network evaluation over a | |||
| over a virtual network. The difference between a simulator and an | virtual network. The difference between a simulator and an emulator | |||
| emulator is that emulators leverage VM or containers to keep the | is that emulators leverage VM or containers to keep the realism which | |||
| realism which is close to actual performances. Therefore, in | is close to actual performances. Therefore, in emulators, virtual | |||
| emulators, virtual nodes. virtual network links, virtual models of | nodes. virtual network links, virtual models of traffic, and | |||
| traffic, and protocols are all applied. Emulators are capable to run | protocols are all applied. Emulators are capable to run real kernel | |||
| real kernel and application code. Thus, emulators not only support | and application code. Thus, emulators not only support diverse | |||
| diverse topology design, but also protocol emulation in a synthetic | topology design, but also protocol emulation in a synthetic network | |||
| network environment. They emulate the network behavior in a more | environment. They emulate the network behavior in a more real way. | |||
| real way. Mininet [Mininet] is commonly regarded as the most | Mininet [Mininet] is commonly regarded as the most illustrious | |||
| illustrious emulator for networking with its strong ability to | emulator for networking with its strong ability to support | |||
| support experiments with Software-Defined Networking (SDN) | experiments with Software-Defined Networking (SDN) | |||
| [Software-defined-networking] systems. EstiNet [EstiNet] is another | [Software-defined-networking] systems. EstiNet [EstiNet] is another | |||
| emulator that supports evaluating and testing the performances of | emulator that supports evaluating and testing the performances of | |||
| software-defined networks. Based on containers, they can emulate | software-defined networks. Based on containers, they can emulate | |||
| real TCP/IP protocol stack in the Linux kernel. However, existing | real TCP/IP protocol stack in the Linux kernel. However, existing | |||
| emulation tools lack the ability to construct the dynamic links and | emulation tools lack the ability to construct the dynamic links and | |||
| orbits in ISTN like simulators. Thus, more problems could happen in | orbits in ISTN like simulators. Thus, more problems could happen in | |||
| higher-level protocols such as routing protocols (e.g. OSPF and | higher-level protocols such as routing protocols (e.g. OSPF and | |||
| BGP). Besides, since emulators run containers or virtual machines | BGP). Besides, since emulators run containers or virtual machines | |||
| which occupy more software overhead, compared with simulators, it | which occupy more software overhead, as compared with simulators, it | |||
| will be hard to emulate the large-scale mega-constellations. | will be hard to emulate the large-scale mega-constellations. | |||
| Existing work has shown the capability of 25 physical machines | ||||
| working together as a system to emulate 250 network nodes, but still, | ||||
| it is far less for ISTN scalability. | ||||
| To conclude, emulators are relatively good methodologies for network | To conclude, emulators are relatively good methodologies for network | |||
| experiments, but emulators still have limitations when using them for | experiments, but emulators still have limitations when using them for | |||
| ISTN research. While keeping a moderate realism by using VM or | ISTN research. While keeping a moderate realism by using VM or | |||
| containers for entity emulation and flexibility, emulators still lack | containers for entity emulation and flexibility, emulators still lack | |||
| the supports for ISTN characteristics, such as frequent link changes, | the supports for ISTN characteristics, such as frequent link changes, | |||
| satellite network topology uncertainty, and so on. More | satellite network topology uncertainty, and so on. More | |||
| specifically, current emulators only support fixed network topology | specifically, current emulators only support fixed network topology | |||
| emulation. It is not flexible to emulate the time-varying link | emulation. It is not flexible to emulate the time-varying link | |||
| packet loss, bandwidth, and other traits. A possible way is to | packet loss, bandwidth, and other traits. A possible way is to | |||
| skipping to change at page 11, line 39 ¶ | skipping to change at page 12, line 8 ¶ | |||
| In addition, it is still difficult to emulate thousands or ten | In addition, it is still difficult to emulate thousands or ten | |||
| thousand of satellites for ISTN even with VM or containers, subject | thousand of satellites for ISTN even with VM or containers, subject | |||
| to hardware limitations. For flexibility, some emulators do not | to hardware limitations. For flexibility, some emulators do not | |||
| support a good network animator tool. Especially in ISTN emulation, | support a good network animator tool. Especially in ISTN emulation, | |||
| GUI is important for users to observe and analyze orbit trajectories | GUI is important for users to observe and analyze orbit trajectories | |||
| and real time satellite positions. | and real time satellite positions. | |||
| 4.4. Summary | 4.4. Summary | |||
| In this section, we explain the necessity of an evaluation | In this section, we explain the necessity of an evaluation | |||
| methodology specifically for ISTN. Then we demonstrate the problems | methodology specifically for ISTNs. Then we demonstrate the problems | |||
| with existing methodologies related to ISTN. The performance | with existing methodologies related to ISTNs. The performance | |||
| comparison result is shown in Table 3. Above all, ISTN should be | comparison result is shown in Table 3. Above all, ISTNs should be | |||
| designed first and then launched. Live satellites enable good | designed first and then launched. Live satellites enable good | |||
| realism but they lack flexibility and require very high cost as well | realism but they lack flexibility and require very high cost as well | |||
| as a very long deployment period. Other testing tools such as | as a very long deployment period. Other testing tools such as | |||
| simulators and emulators are either functional for merely aerospace | simulators and emulators are either functional for merely aerospace | |||
| analysis or simply terrestrial networks. None of the existing | analysis or simply terrestrial networks. None of the existing | |||
| methodologies guarantees a practical and user-friendly methodology | methodologies guarantees a practical and user-friendly methodology | |||
| while keeping the evaluation environment realism with low costs. | while keeping the evaluation environment realism with low costs. | |||
| +================+=========+=============+======+=================+ | +================+=========+=============+======+=================+ | |||
| | Platform/Tool | Realism | Flexibility | Cost | Cross-domain | | | Platform/Tool | Realism | Flexibility | Cost | Cross-domain | | |||
| skipping to change at page 12, line 39 ¶ | skipping to change at page 13, line 8 ¶ | |||
| A proper evaluation methodology tailored for ISTNs is expected to | A proper evaluation methodology tailored for ISTNs is expected to | |||
| help developers, researchers, engineers to explore various design- | help developers, researchers, engineers to explore various design- | |||
| space of the networking stack of ISTNs in a technically and | space of the networking stack of ISTNs in a technically and | |||
| economically feasible manner. Based on the comparative analysis | economically feasible manner. Based on the comparative analysis | |||
| results in the prior section, we sum up the following requirements | results in the prior section, we sum up the following requirements | |||
| for the new evaluation methodology in ISTNs. | for the new evaluation methodology in ISTNs. | |||
| 5.1. Realism | 5.1. Realism | |||
| The first requirement is realism. Realism represents the testing | The first requirement is realism. Realism represents the testing | |||
| authenticity and fidelity, compared with real ISTN. It could be | authenticity and fidelity. The evaluation methodology is expected to | |||
| further divided into constellation-consistency and networking stack | keep the actual characteristics of mega-constellations. In other | |||
| realism. Constellation-consistency requires the testing to keep the | words, the orbit-level information including the latitude, longitude, | |||
| actual characteristics of mega-constellations both spatially and | and height of each satellite in any given time and the same | |||
| temporally. In other words, the orbit-level information including | information for GS and elevation angles of antennas of each GS. Note | |||
| the latitude, longitude, and height of each satellite in any given | that the constellation information also determines the visibility, | |||
| time and the same information for GS and elevation angles of antennas | links and even topology of ISTN.s Since the mega-constellations are | |||
| of each GS spatially. Note that the spatial information also | unstable, how the temporal satellite locations, visibility, link | |||
| determines the visibility, links and even topology of ISTN. Since | propagation delays and so on should also be considered carefully. In | |||
| the mega-constellations are unstable, how the temporal satellite | addition, it requires the network nodes to communicate and negotiate | |||
| locations, visibility, link propagation delays and so on should also | their messages following the actual protocol process. For example, | |||
| be considered carefully. Similarly, the networking stack realism | when doing a test for OSPF in an ISTN, we would like the nodes to | |||
| requires the network nodes to communicate and negotiate their | send Hello packets, Link-State-Request (LSR) packets, Link-State- | |||
| messages following the actual protocol process. For example, when | Update (LSU) packets and so on. A real network stack is preferred to | |||
| doing a test for OSPF in an ISTN, we would like the nodes to send | ||||
| Hello packets, Link-State-Request (LSR) packets, Link-State-Update | ||||
| (LSU) packets and so on. A real network stack is preferred to | ||||
| provide researchers an opportunity to see the performance of | provide researchers an opportunity to see the performance of | |||
| different protocols in ISTN. | different protocols in ISTNs. | |||
| 5.2. Flexibility | 5.2. Flexibility | |||
| Another requirement is flexibility and feasibility. The testing | Another requirement is flexibility and feasibility. The testing | |||
| methodology should be technically easy to use and easy to learn. | methodology should be technically easy to use and easy to learn. | |||
| Without extra modifications or process, the methodology should help | Without extra modifications or process, the methodology should help | |||
| researchers learn and use it without much effort and can evaluate | researchers learn and use it without much effort and can evaluate | |||
| their ideas as they wish, which means it should support multiple | their ideas as they wish, which means it should support flexible, | |||
| environments for researchers. | controllable environments for researchers. | |||
| 5.3. Low-cost and Easy-to-use | 5.3. Low-cost and Easy-to-use | |||
| Meanwhile, the evaluation methodology is expected to be low-cost. A | Meanwhile, the evaluation methodology is expected to be low-cost. A | |||
| well-acceptable methodology should be economically feasible for users | well-acceptable methodology should be economically feasible for users | |||
| to create an experimental network environment. Researchers do not | to create an evaluation environment. Researchers do not want to | |||
| want to conduct their tests all in live ISTN, which is over- | conduct their tests all in live ISTN, which is over-cumbersome and | |||
| cumbersome and unaffordable, let alone launching their own | unaffordable, let alone launching their own spacecraft. Even if | |||
| spacecraft. Even if there are a number of orbiting satellites, | there are a number of orbiting satellites, whether users can easily | |||
| whether users can easily gain access to satellites is also a problem. | gain access to satellites is also a problem. | |||
| 5.4. Cross-domain Dataset Support | 5.4. Cross-domain Dataset Support | |||
| The evaluation methodology is expected to be driven by realistic | The evaluation methodology is expected to be driven by realistic | |||
| datasets from multi-dimensions to support its realism. Multi- | datasets from multi-dimensions to support its realism. Multi- | |||
| dimension refers to multi-disciplinary research on ISTN. Since a | dimension refers to multi-disciplinary research on ISTNs. Since a | |||
| standard ISTN evaluation methodology not only contains high-level | standard ISTN evaluation methodology not only contains high-level | |||
| benchmarks from topology, routing to transmission, but also considers | benchmarks from topology, routing to transmission, but also considers | |||
| the low-level traits such as wireless link conditions, weather | the low-level traits such as wireless link conditions, weather | |||
| conditions and Earth rotations. To be more concrete, the former one | conditions and Earth rotations. To be more concrete, the former one | |||
| requires knowledge in networks while the latter one relies more on | requires knowledge in networks while the latter one relies more on | |||
| aerospace. Hence, to build a high-fidelity methodology, we need | aerospace. Hence, to build a high-fidelity methodology, we need | |||
| community efforts both from networks and aerospace. On the other | community efforts both from networks and aerospace. On the other | |||
| hand, an authentic dataset is an indispensable element for data | hand, an authentic dataset is an indispensable element for data | |||
| driven testing methodology. Actual data is the first step to obtain | driven testing methodology. Actual data is the first step to obtain | |||
| a realistic emulation. with characteristics of a real ISTN. Thus, | a realistic emulation. with characteristics of a real ISTN. Thus, | |||
| skipping to change at page 16, line 11 ¶ | skipping to change at page 16, line 19 ¶ | |||
| [PlanetLab] | [PlanetLab] | |||
| "PlanetLab", <https://citeseerx.ist.psu.edu/viewdoc/ | "PlanetLab", <https://citeseerx.ist.psu.edu/viewdoc/ | |||
| download?doi=10.1.1.99.7006&rep=rep1&type=pdf>. | download?doi=10.1.1.99.7006&rep=rep1&type=pdf>. | |||
| [Production-Cycles] | [Production-Cycles] | |||
| "Production-Cycles", | "Production-Cycles", | |||
| <http://www.futron.com/upload/wysiwyg/Resources/ | <http://www.futron.com/upload/wysiwyg/Resources/ | |||
| Whitepapers/Satellite_Manufacturing_Productio | Whitepapers/Satellite_Manufacturing_Productio | |||
| n_Cycles_0504.pdf>. | n_Cycles_0504.pdf>. | |||
| [RAD5545] "RAD5545", <https://www.baesystems.com/en-media/ | ||||
| uploadFile/20210407074148/1434594567983.pdf>. | ||||
| [RAD750] "RAD750", <https://www.baesystems.com/en-media/ | ||||
| uploadFile/20210407041505/1434555689265.pdf>. | ||||
| [raspberry-pi] | ||||
| "raspberry-pi", <https:// www.raspberrypi.com/news/ | ||||
| raspberry-pi-in-space/>. | ||||
| [Software-defined-networking] | [Software-defined-networking] | |||
| "Software-defined-networking", | "Software-defined-networking", | |||
| <https://en.wikipedia.org/wiki/Software- | <https://en.wikipedia.org/wiki/Software- | |||
| defined_networking>. | defined_networking>. | |||
| [Sparta] "Sparta", <https://s3-us-west- | [Sparta] "Sparta", <https://s3-us-west- | |||
| 2.amazonaws.com/ieeeshutpages/xplore/xplore-shut- | 2.amazonaws.com/ieeeshutpages/xplore/xplore-shut- | |||
| page.html>. | page.html>. | |||
| [Starlink] "Starlink", <https://en.wikipedia.org/wiki/Starlink>. | [Starlink] "Starlink", <https://en.wikipedia.org/wiki/Starlink>. | |||
| skipping to change at page 16, line 45 ¶ | skipping to change at page 17, line 17 ¶ | |||
| 20200526-00053/2378318.pdf>. | 20200526-00053/2378318.pdf>. | |||
| Authors' Addresses | Authors' Addresses | |||
| Zeqi Lai | Zeqi Lai | |||
| Tsinghua University | Tsinghua University | |||
| 30 ShuangQing Ave | 30 ShuangQing Ave | |||
| Beijing | Beijing | |||
| 100089 | 100089 | |||
| China | China | |||
| Email: zeqilai@tsinghua.edu.cn | Email: zeqilai@tsinghua.edu.cn | |||
| Hewu Li | Hewu Li | |||
| Tsinghua University | Tsinghua University | |||
| 30 ShuangQing Ave | 30 ShuangQing Ave | |||
| Beijing | Beijing | |||
| 100089 | 100084 | |||
| China | China | |||
| Email: lihewu@cernet.edu.cn | Email: lihewu@cernet.edu.cn | |||
| Yangtao Deng | Yangtao Deng | |||
| Tsinghua University | Tsinghua University | |||
| 30 ShuangQing Ave | 30 ShuangQing Ave | |||
| Beijing | Beijing | |||
| 100089 | 100084 | |||
| China | China | |||
| Email: dengyt21@mails.tsinghua.edu.cn | Email: dengyt21@mails.tsinghua.edu.cn | |||
| Qian Wu | Qian Wu | |||
| Tsinghua University | Tsinghua University | |||
| 30 ShuangQing Ave | 30 ShuangQing Ave | |||
| Beijing | Beijing | |||
| 100089 | 100084 | |||
| China | China | |||
| Email: wuqian@cernet.edu.cn | Email: wuqian@cernet.edu.cn | |||
| Jun Liu | Jun Liu | |||
| Tsinghua University | Tsinghua University | |||
| 30 ShuangQing Ave | 30 ShuangQing Ave | |||
| Beijing | Beijing | |||
| 100089 | 100084 | |||
| China | China | |||
| Email: juneliu@mail.tsinghua.edu.cn | Email: juneliu@mail.tsinghua.edu.cn | |||
| End of changes. 48 change blocks. | ||||
| 121 lines changed or deleted | 138 lines changed or added | |||
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