



TSVWG                                                            F. Yang
Internet-Draft                                              China Mobile
Intended status: Informational                                   T. Tsou
Expires: 13 December 2025                                         Tiktok
                                                            11 June 2025


         Transport Layer Protocol Requirement for LEO satellite
                 draft-yang-tsvwg-leo-transport-req-01

Abstract

   In recent years, high-bandwidth LEO (Low Earth Orbit) satellite
   networks, such as Starlink and OneWeb, have seen tremendous
   development and are gradually becoming an important part of the
   global Internet.  However, due to the unique characteristics of
   satellite networks, using TCP for data transmission faces challenges
   in multiple aspects, such as high latency caused by long-distance
   propagation and high error rates due to signal attenuation.  This
   proposal summarizes the basic requirements that need to be considered
   for designing transport layer protocols tailored to LEO satellites.

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
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   This Internet-Draft will expire on 13 December 2025.

Copyright Notice

   Copyright (c) 2025 IETF Trust and the persons identified as the
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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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   and restrictions with respect to this document.  Code Components
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   provided without warranty as described in the Revised BSD License.

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
     1.1.  Requirements Language . . . . . . . . . . . . . . . . . .   2
   2.  Requirement for transport layer protocol  . . . . . . . . . .   3
   3.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   4
   4.  Security Considerations . . . . . . . . . . . . . . . . . . .   4
   5.  References  . . . . . . . . . . . . . . . . . . . . . . . . .   4
     5.1.  Normative References  . . . . . . . . . . . . . . . . . .   4
     5.2.  Informative References  . . . . . . . . . . . . . . . . .   4
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .   5

1.  Introduction

   In recent years, high-bandwidth LEO (Low Earth Orbit) satellite
   networks, such as Starlink and OneWeb, have seen tremendous
   development and are gradually becoming an important part of the
   global Internet.  However, due to the unique characteristics of
   satellite networks, using TCP for data transmission faces challenges
   in multiple aspects, such as high latency caused by long-distance
   propagation and high error rates due to signal attenuation.  This
   proposal summarizes the basic requirements that need to be considered
   for designing transport layer protocols tailored to LEO satellites.

   The factors mentioned in [I-D.LEOTransPS], such as bursty packet
   losses, variable round-trip times, and variable link rates, will
   greatly impact the performance of TCP.

   Various optimizations at the transport protocol level have been
   proposed, such as end-to-end optimizations like SCPS-TP and MP-TCP,
   redundancy coding like FEC, cross-layer optimizations like ECN, and
   congestion control algorithm optimizations like TCP Westwood and TCP
   Eifel, as well as AI-enhanced congestion control.  This gives us some
   indications on what problem we should focused on.

1.1.  Requirements Language

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
   "OPTIONAL" in this document are to be interpreted as described in
   BCP 14 [RFC2119] [RFC8174] when, and only when, they appear in all
   capitals, as shown here.




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2.  Requirement for transport layer protocol

   Given the unique characteristics of LEO satellite networks, the
   requirements for transport layer protocols should focus on improving
   the following aspects:

   Fast Connection Establishment.  In satellite networks, fast
   connection establishment is crucial for improving communication
   efficiency.  For short-lived communication needs, such as bursty data
   transmission from mobile users, a slow connection setup process can
   waste significant time.  TCP needs to optimize its connection
   establishment process by adopting fast handshake algorithms and other
   techniques to reduce the time required for connection setup and
   enhance the responsiveness of satellite networks.

   High-Bandwidth Support.  High-performance transport protocols aim to
   support the rapid transmission of large volumes of data, such as
   high-definition video streaming and big data file transfers.  When
   sufficient bandwidth capacity is available in the satellite link, the
   protocol should provide high-bandwidth transmission capabilities to
   meet the demands of these applications.

   Adaptation to Latency Variations.  The latency in satellite networks
   may fluctuate due to factors such as satellite handovers and signal
   interference, causing RTT (Round-Trip Time) jitter.  Transport
   protocols need to quickly adapt to this latency jitter to avoid
   performance degradation resulting from congestion window changes
   triggered by the jitter.

   Error Resistance.  Data packet loss in satellite channels can be
   caused by obstructions, atmospheric interference, and spatial
   distance.  More efficient packet loss detection and recovery
   mechanisms are needed.  For example, redundancy-based encoding
   methods can be introduced, where the sender encodes data with
   redundancy, and the receiver can use this redundant information to
   recover lost packets, reducing the need for retransmissions and
   enhancing the reliability of data transmission.

   Resilience to Network Interruptions.  Short-term interruptions in
   satellite links can easily occur due to sun outages or satellite
   coverage limitations.  During such interruptions, the transport
   protocol should reduce the sending rate to minimize unnecessary
   packet transmission.  Once the interruption is resolved, the protocol
   should quickly restore the bandwidth to ensure efficient data
   transfer.






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   Reduced Retransmission Rate.  Retransmissions increase transmission
   delay and consume bandwidth, which are particularly valuable
   resources in satellite networks.  Transport protocols need to
   minimize unnecessary retransmissions through accurate packet loss
   detection and effective error recovery mechanisms, thereby optimizing
   the overall efficiency of data transmission.

   Improved Out-of-Order Handling.  The complex transmission environment
   in satellite networks can cause packets to arrive out of order at the
   receiver due to different routing paths and varying transmission
   delays.  Transport protocols must be capable of accurately reordering
   out-of-order packets to ensure the correct delivery of data.

3.  IANA Considerations

   N/A.

4.  Security Considerations

   N/A.

5.  References

5.1.  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/rfc/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/rfc/rfc8174>.

5.2.  Informative References

   [I-D.LEOTransPS]
              Feng, Y., "draft-yang-tsvwg-leo-transport-problem-
              statement", 2025, <https://datatracker.ietf.org/doc/draft-
              yang-tsvwg-leo-transport-problem-statement/>.

   [Izhikevich2024]
              Liz, I., Reese, E., Te-Yuan, H., and T. Renata, "A Global
              Perspective on the Past, Present, and Future of Video
              Streaming over Starlink", 2024,
              <https://doi.org/10.1145/3700412>.





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   [Hu2023]   Bin, H., Xumiao, Z., Qixin, Z., Nitin, V., Morley, M. Z.,
              Feng, Q., and Z. Zhi-Li, "LEO Satellite vs. Cellular
              Networks: Exploring the Potential for Synergistic
              Integration", 2023,
              <https://doi.org/10.1145/3624354.3630588>.

   [Li2024]   Jihao, L., Hewu, L., Zeqi, L., Qian, W., Yijie, L., Qi,
              Z., Yuanjie, L., and L. Jun, "SatGuard: Concealing Endless
              and Bursty Packet Losses in LEO Satellite Networks for
              Delay-Sensitive Web Applications", 2024,
              <https://doi.org/10.1145/3589334.3645639>.

   [I-D.LSNCC]
              Lai, Z., Li, Z., Wu, Q., Li, H., and Q. Zhang, "Analysis
              for the Adverse Effects of LEO Mobility on Internet
              Congestion Control", 2024,
              <https://datatracker.ietf.org/doc/draft-lai-ccwg-
              lsncc/00/>.

Authors' Addresses

   Feng Yang
   China Mobile
   Beijing
   China
   Email: yangfeng@chinamobile.com


   Tina Tsou
   Tiktok
   San Jose,
   United States of America
   Email: tina.tsou@tiktok.com


















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