Network coding for satellite systems
draft-irtf-nwcrg-network-coding-satellites-09

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Internet Engineering Task Force                             N. Kuhn, Ed.
Internet-Draft                                                      CNES
Intended status: Informational                            E. Lochin, Ed.
Expires: June 13, 2020                                      ISAE-SUPAERO
                                                       December 11, 2019

                  Network coding for satellite systems
             draft-irtf-nwcrg-network-coding-satellites-09

Abstract

   This document is the product of the Coding for Efficient Network
   Communications Research Group (NWCRG).  It conforms to the directions
   found in the NWCRG taxonomy [RFC8406].  Thus, the scope of the
   document is network coding as a linear combination of packets in and
   above the network layer.  Physical and MAC layer coding are beyond
   the scope of the document.  The draft focuses on a multi-gateway
   satellite system and identifies the use-cases where network coding
   provides significant performance improvements.  The objective is to
   contribute to a larger deployment of network coding techniques in
   SATCOM to complement already implemented loss recovery mechanisms.
   The draft also identifies open research issues related to the
   deployment of network coding in SATCOM systems.

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 June 13, 2020.

Copyright Notice

   Copyright (c) 2019 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 and restrictions with respect
   to this document.  Code Components extracted from this document must
   include Simplified BSD License text as described in Section 4.e of
   the Trust Legal Provisions and are provided without warranty as
   described in the Simplified BSD License.

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
   2.  A Note on Satellite Networks Topology . . . . . . . . . . . .   3
   3.  Use-cases for Improving SATCOM System Performance Using
       Network Coding  . . . . . . . . . . . . . . . . . . . . . . .   5
     3.1.  Two-way Relay Channel Mode  . . . . . . . . . . . . . . .   5
     3.2.  Reliable Multicast  . . . . . . . . . . . . . . . . . . .   5
     3.3.  Hybrid Access . . . . . . . . . . . . . . . . . . . . . .   6
     3.4.  LAN Packet Losses . . . . . . . . . . . . . . . . . . . .   7
     3.5.  Varying Channel Conditions  . . . . . . . . . . . . . . .   8
     3.6.  Improving Gateway Handover  . . . . . . . . . . . . . . .   8
   4.  Research Challenges . . . . . . . . . . . . . . . . . . . . .   9
     4.1.  Joint-use of Network Coding and Congestion Control in
           SATCOM Systems  . . . . . . . . . . . . . . . . . . . . .   9
     4.2.  Efficient Use of Satellite Resources  . . . . . . . . . .  10
     4.3.  Interaction with Virtualized Satellite Gateways and
           Terminals . . . . . . . . . . . . . . . . . . . . . . . .  10
     4.4.  Delay/Disruption Tolerant Networks  . . . . . . . . . . .  10
   5.  Conclusion  . . . . . . . . . . . . . . . . . . . . . . . . .  11
   6.  Glossary  . . . . . . . . . . . . . . . . . . . . . . . . . .  11
   7.  Acknowledgements  . . . . . . . . . . . . . . . . . . . . . .  13
   8.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .  13
   9.  Security Considerations . . . . . . . . . . . . . . . . . . .  13
   10. Informative References  . . . . . . . . . . . . . . . . . . .  13
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  15

1.  Introduction

   This document is the product of and represents the collaborative work
   and consensus of the Coding for Efficient Network Communications
   Research Group (NWCRG); while it is not an IETF product and not a
   standard it intends to inform the SATCOM and Internet research
   communities about recent developments in Network Coding.  A glossary
   is proposed in Section 6 to clarify the terminology use throughout
   the document.

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   As will be shown in this draft, the implementation of network coding
   techniques above the network layer of the ISO model, at application
   or transport layers, offers an opportunity for improving the end-to-
   end performance of SATCOM systems.  While physical- and link-layer
   coding error protection is usually enough to provide Quasi-Error Free
   transmission thus minimizing packet loss, when the physical and link
   layers coding fail or that residual errors create packet losses that
   greatly interfere with Internet protocols, retransmissions add
   significant delays because especially in geostationary system with
   over 0.7 second round-trip delays.  Hence the use of network coding
   at the upper layers can improve the quality of service in SATCOM
   subnetworks and eventually favorably impact the experience of end
   users.

   While there is an active research Community working on network coding
   techniques above the network layer in general and in SATCOM in
   particular, not much of this work made it to commercial systems in
   the satellite industry.  In this context, this document aims at
   identifying opportunities for further usage of network coding in
   commercial SATCOM networks.

   The notation used in this document is based on the NWCRG taxonomy
   [RFC8406]:

   o  Channel and link error correcting codes are considered part of the
      PHY layer error protection and are out of the scope of this
      document.

   o  FEC (also called Application-Level FEC) operates in and above the
      network layer and targets packet loss recovery.

   o  This document considers only coding (or coding techniques or
      coding schemes) that use a linear combination of packets and
      excludes for example content coding (e.g., to compress a video
      flow) or other non-linear operation.

2.  A Note on Satellite Networks Topology

   There are multiple SATCOM systems, for example broadcast TV, point to
   point communication or IoT and monitoring.  Therefore, depending on
   the purpose of the system, the associated ground segments
   architecture will be different.  This section focuses on a satellite
   system that follows the ETSI DVB standards to provide broadband
   Internet access via ground-based gateways.  One must note that the
   overall data capacity of one satellite may be higher than the
   capacity that one single gateway support.  Hence, there are usually
   multiple gateways for one unique satellite platform.

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   In this context, Figure 1 shows an example of a multi-gateway
   satellite system.  More information on a generic SATCOM ground
   segment architecture for bidirectional Internet access can be found
   in [SAT2017].

   +--------------------------+
   | application servers      |
   | (data, coding, multicast)|
   +--------------------------+
          | ... |
          -----------------------------------
          |     |   |             |   |     |
   +--------------------+     +--------------------+
   | network function   |     | network function   |
   |(firewall, PEP, etc)|     |(firewall, PEP, etc)|
   +--------------------+     +--------------------+
       | ... | IP packets             |  ...   |
                                                   ---
   +------------------+         +------------------+ |
   | access gateway   |         | access gateway   | |
   +------------------+         +------------------+ |
          | BBFRAME                         |        | gateway
   +------------------+         +------------------+ |
   | physical gateway |         | physical gateway | |
   +------------------+         +------------------+ |
                                                   ---
          | PLFRAME                         |
   +------------------+         +------------------+
   | outdoor unit     |         | outdoor unit     |
   +------------------+         +------------------+
          | satellite link                  |
   +------------------+         +------------------+
   | outdoor unit     |         | outdoor unit     |
   +------------------+         +------------------+
          |                                 |
   +------------------+         +------------------+
   | sat terminals    |         | sat terminals    |
   +------------------+         +------------------+
          |        |                  |        |
   +----------+    |            +----------+   |
   |end user 1|    |            |end user 3|   |
   +----------+    |            +----------+   |
             +----------+               +----------+
             |end user 2|               |end user 4|
             +----------+               +----------+

    Figure 1: Data plane functions in a generic satellite multi-gateway
       system.  More details can be found in DVB standard documents.

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3.  Use-cases for Improving SATCOM System Performance Using Network
    Coding

   This section details use-cases where network coding techniques could
   improve SATCOM system performance.

3.1.  Two-way Relay Channel Mode

   This use-case considers two-way communication between end-users,
   through a satellite link as seen in Figure 2.

   Satellite terminal A sends a packet flow A and satellite terminal B
   sends a packet flow B to a coding server.  The coding server then
   sends a combination of both flows instead of each individual flows.
   This results in non-negligible capacity savings that has been
   demonstrated in the past [ASMS2010].  In the example, a dedicated
   coding server is introduced (note that its location could be
   different based on deployment use-case).  The network coding
   operations could also be done at the satellite level, although this
   would require a lot of computational resource on-board and may not be
   supported by today's satellites.

   -X}-   : traffic from satellite terminal X to the server
   ={X+Y= : traffic from X and Y combined sent from
               the server to terminals X and Y

   +-----------+        +-----+
   |Sat term A |--A}-+  |     |
   +-----------+     |  |     |      +---------+      +------+
       ^^            +--|     |--A}--|         |--A}--|Coding|
       ||               | SAT |--B}--| Gateway |--B}--|Server|
       ===={A+B=========|     |={A+B=|         |={A+B=|      |
       ||               |     |      +---------+      +------+
       vv            +--|     |
   +-----------+     |  |     |
   |Sat term B |--B}-+  |     |
   +-----------+        +-----+

     Figure 2: Network Architecture for Two-way Relay Channel using NC

3.2.  Reliable Multicast

   The use of multicast servers is one way to better utilize a satellite
   broadcast capabilities.  Multicast is proposed in the SHINE ESA
   project [I-D.vazquez-nfvrg-netcod-function-virtualization] [SHINE].
   This use-case considers adding redundancy to a multicast flow
   depending on what has been received by different end-users, resulting

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   in non-negligible savings of the scarce SATCOM resources.  This
   scenario is shown in Figure 3.

   -Li}- : packet indicating the loss of packet i of a multicast flow M
   ={M== : multicast flow including the missing packets

   +-----------+       +-----+
   |Sat term A |-Li}-+ |     |
   +-----------+     | |     |      +---------+  +------+
       ^^            +-|     |-Li}--|         |  |Multi |
       ||              | SAT |-Lj}--| Gateway |--|Cast  |
       ===={M==========|     |={M===|         |  |Server|
       ||              |     |      +---------+  +------+
       vv            +-|     |
   +-----------+     | |     |
   |Sat term B |-Lj}-+ |     |
   +-----------+       +-----+

     Figure 3: Network Architecture for a Reliable Multicast using NC

   A multicast flow (M) is forwarded to both satellite terminals A and
   B.  However packet Ni (respectively Nj) gets lost at terminal A
   (respectively B), and terminal A (respectively B) returns a negative
   acknowledgment Li (respectively Lj), indicating that the packet is
   missing.  Using NC, either the access gateway or the multicast server
   can include a repair packet (rather than the individual Ni and Nj
   packets) in the multicast flow to let both terminals recover from
   losses.

   This could also be achieved by using other multicast or broadcast
   systems, such as NACK-Oriented Reliable Multicast (NORM) [RFC5740] or
   File Delivery over Unidirectional Transport (FLUTE) [RFC6726].  Both
   NORM and FLUTE are limited to block coding, none of them supporting
   more flexible sliding window encoding schemes that allow decoding
   before receiving the whole block an added delay benefit [RFC8406].

3.3.  Hybrid Access

   This use-case considers improving multiple path communications with
   network coding at the transport layer (see Figure 4).  This use-case
   is inspired by the Broadband Access via Integrated Terrestrial
   Satellite Systems (BATS) project and has been published as an ETSI
   Technical Report [ETSITR2017].

   To cope with packet loss (due to either end-user mobility or
   physical-layer residual errors), network coding can be introduced
   both at the CPE and at the concentrator.  Apart from packet losses,
   other gains from this approach include a better tolerance to out-of-

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   order packet delivery which occur when exploited links exhibit high
   asymmetry in terms of RTT.  Depending on the ground architecture
   [I-D.chin-nfvrg-cloud-5g-core-structure-yang] [SAT2017], some ground
   equipment might be hosting both SATCOM and cellular network
   functionality.

   -{}- : bidirectional link

                           +---+    +--------------+
                      +-{}-|SAT|-{}-|BACKBONE      |
   +----+    +---+    |    +---+    |+------------+|
   |End |-{}-|CPE|-{}-|             ||CONCENTRATOR||
   |User|    +---+    |    +---+    |+------------+|    +-----------+
   +----+             |-{}-|DSL|-{}-|              |-{}-|Application|
                      |    +---+    |              |    |Server     |
                      |             |              |    +-----------+
                      |    +---+    |              |
                      +-{}-|LTE|-{}-+--------------+
                           +---+

     Figure 4: Network Architecture for a Hybrid Access Using Network
                                  Coding

3.4.  LAN Packet Losses

   This use-case considers using network coding in the scenario where a
   lossy WIFI link is used to connect to the SATCOM network.  When
   encrypted end-to-end applications based on UDP are used, a PEP cannot
   operate hence other mechanism need to be used.  The WIFI packet
   losses will result in an end-to-end retransmission that will harm the
   end-user quality of experience and poorly utilize SATCOM bottleneck
   resource for non-revenue generating traffic.  In this use-case,
   adding network coding techniques will prevent the end-to-end
   retransmission from occurring since the packet losses will be
   recovered.

   The architecture is shown in Figure 5.

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 -{}- : bidirectional link
 -''- : Wi-Fi link
 C : where network coding techniques could be introduced

 +----+    +---------+    +---+    +--------+    +-------+    +--------+
 |End |    |Satellite|    |SAT|    |Physical|    |Access |    |Network |
 |user|-''-|Terminal |-{}-|   |-{}-|Gateway |-{}-|Gateway|-{}-|Function|
 +----+    +---------+    +---+    +--------+    +-------+    +--------+
    C                       C            C           C

        Figure 5: Network Architecture for dealing with LAN Losses

3.5.  Varying Channel Conditions

   This use-case considers the usage of network coding to cope with sub
   second physical channel condition changes where the physical-layer
   mechanisms (Adaptive Coding and Modulation (ACM)) may not adapt the
   modulation and error-correction coding in time: the residual errors
   lead to higher layer packet losses that can be recovered with network
   coding.  This use-case is mostly relevant when mobile users are
   considered or when the satellite frequency band introduces quick
   changes in channel condition (Q/V bands, Ka band, etc.).  Depending
   on the use-case (e.g., very high frequency bands, mobile users) or
   depending on the deployment use-cases (e.g., performance of the
   network between each individual data block), the relevance of adding
   network coding is different.

   The system architecture is shown in Figure 6.

   -{}- : bidirectional link
   C : where network coding techniques could be introduced

   +---------+    +---+    +--------+    +-------+    +--------+
   |Satellite|    |SAT|    |Physical|    |Access |    |Network |
   |Terminal |-{}-|   |-{}-|Gateway |-{}-|Gateway|-{}-|Function|
   +---------+    +---+    +--------+    +-------+    +--------+
        C                       C            C           C

       Figure 6: Network Architecture for dealing with Varying Link
                              Characteristics

3.6.  Improving Gateway Handover

   This use-case considers the recovery of packets that may be lost
   during gateway handover.  Whether for off-loading a given equipment
   or because the transmission quality differs from gateway to gateway,
   switching the transmission gateway may be beneficial.  However,
   packet losses can occur if the gateways are not properly synchronized

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   or if the algorithm used to trigger gateway handover is not properly
   tuned.  During these critical phases, network coding can be added to
   improve the reliability of the transmission and allow a seamless
   gateway handover.

   Figure 7 illustrates this use-case.

   -{}- : bidirectional link
   !   : management interface
   C : where network coding techniques could be introduced
                                           C             C
                         +--------+    +-------+    +--------+
                         |Physical|    |Access |    |Network |
                    +-{}-|gateway |-{}-|gateway|-{}-|function|
                    |    +--------+    +-------+    +--------+
                    |                        !       !
   +---------+    +---+              +---------------+
   |Satellite|    |SAT|              | Control plane |
   |Terminal |-{}-|   |              | manager       |
   +---------+    +---+              +---------------+
                    |                        !       !
                    |    +--------+    +-------+    +--------+
                    +-{}-|Physical|-{}-|Access |-{}-|Network |
                         |gateway |    |gateway|    |function|
                         +--------+    +-------+    +--------+
                                           C             C

     Figure 7: Network Architecture for dealing with Gateway Handover

4.  Research Challenges

   This section proposes a few potential approaches to introduce and use
   network coding in SATCOM systems.

4.1.  Joint-use of Network Coding and Congestion Control in SATCOM
      Systems

   Many SATCOM systems typically use Performance Enhancing Proxy (PEP)
   RFC 3135 [RFC3135].  PEPs usually split end-to-end connections and
   forward transport or application layer packets to the satellite
   baseband gateway that deals with layer-2 and layer-1 encapsulation.
   PEPs contribute to mitigate congestion in a SATCOM systems by
   limiting the impact of long delays on Internet protocols.  A PEP
   mechanism could also include network coding operation and thus
   support the use-cases that have been discussed in the Section 3 of
   this document.

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   Deploying network coding in the PEP could be relevant and be
   independent from the specifics of a SATCOM link.  This however leads
   to research questions dealing with the potential interaction between
   network coding and congestion control.

4.2.  Efficient Use of Satellite Resources

   There is a recurrent trade-off in SATCOM systems: how much overhead
   from redundant reliability packets can be introduced to guarantee a
   better end-user QoE while optimizing capacity usage ? At which layer
   this supplementary redundancy should be added ?

   This problem has been tackled in the past by the deployment of
   physical-layer error-correction codes, but there remains questions on
   adapting the coding overhead and added delay for, e.g., the quickly
   varying channel conditions use-case where ACM may not be reacting
   quickly enough as was discussed on the previous section.

4.3.  Interaction with Virtualized Satellite Gateways and Terminals

   In the emerging virtualized network infrastructure, network coding
   could be easily deployed as a VNF.  The next generation of SATCOM
   ground segments will rely on a virtualized environment to integrate
   to terrestrial networks.  This trend towards NFV is also central to
   5G and next generation cellular networks, making this research
   applicable to other deployment scenarios
   [I-D.chin-nfvrg-cloud-5g-core-structure-yang].  As one example, the
   network coding VNF deployment in a virtualized environment has been
   presented in [I-D.vazquez-nfvrg-netcod-function-virtualization].

   A research challenge would be the optimization of the NFV service
   function chaining, considering a virtualized infrastructure and other
   SATCOM specific functions, in order to guarantee efficient radio-link
   usage and provide easy-to-deploy SATCOM services.  Moreover, another
   challenge related to a virtualized SATCOM equipment is the management
   of limited buffered capacities in large gateways.

4.4.  Delay/Disruption Tolerant Networks

   Communications among deep-space platforms and terrestrial gateways
   can be a challenge.  Reliable end-to-end (E2E) communications over
   such paths must cope with very long delays and frequent link
   disruptions; indeed, E2E connectivity may be available only
   intermittently.  Delay/Disruption Tolerant Networking [RFC4838] is a
   solution to enable reliable internetworking space communications
   where both standard ad-hoc routing and E2E Internet protocols cannot
   be used.  Moreover, DTN can also be seen as an alternative solution
   to transfer data between a central PEP and a remote PEP.

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   Network Coding enables E2E reliable communications over a DTN with
   potential adaptive re-encoding, as proposed in [THAI15].  Here, the
   use-cases proposed in Section 3.5 would legitimize the usage of
   network coding within the DTN stack to improve the physical channel
   utilization and minimize the effects of the E2E transmission delays.
   In this context, the use of packet erasure coding techniques inside a
   Consultative Committee for Space Data Systems (CCSDS) architecture
   has been specified in [CCSDS-131.5-O-1].  One research challenge
   remains on how such network coding can be integrated in the IETF DTN
   stack.

5.  Conclusion

   This document introduces some wide-scale network coding techniques
   opportunities in satellite telecommunications systems.

   Even though this document focuses on satellite systems, it is worth
   pointing out that some scenarios proposed here may be relevant to
   other wireless telecommunication systems.  As one example, the
   generic architecture proposed in Figure 1 may be mapped onto cellular
   networks as follows: the 'network function' block gathers some of the
   functions of the Evolved Packet Core subsystem, while the 'access
   gateway' and 'physical gateway' blocks gather the same type of
   functions as the Universal Mobile Terrestrial Radio Access Network.
   This mapping extends the opportunities identified in this draft since
   they may also be relevant for cellular networks.

6.  Glossary

   The glossary of this memo extends the glossary of the taxonomy
   document [RFC8406] as follows:

   o  ACM : Adaptive Coding and Modulation;

   o  BBFRAME: Base-Band FRAME - satellite communication layer 2
      encapsulation work as follows: (1) each layer 3 packet is
      encapsulated with a Generic Stream Encapsulation (GSE) mechanism,
      (2) GSE packets are gathered to create BBFRAMEs, (3) BBFRAMEs
      contain information related to how they have to be modulated (4)
      BBFRAMEs are forwarded to the physical-layer;

   o  CPE: Customer Premises Equipment;

   o  COM: COMmunication;

   o  DSL: Digital Subscriber Line;

   o  DTN: Delay/Disruption Tolerant Network;

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   o  DVB: Digital Video Broadcasting;

   o  E2E: End-to-end;

   o  ETSI: European Telecommunications Standards Institute;

   o  FEC: Forward Erasure Correction;

   o  FLUTE: File Delivery over Unidirectional Transport;

   o  IntraF: Intra-Flow Coding;

   o  InterF: Inter-Flow Coding;

   o  IoT: Internet of Things;

   o  LTE: Long Term Evolution;

   o  MPC: Multi-Path Coding;

   o  NC: Network Coding;

   o  NFV: Network Function Virtualization;

   o  NORM: NACK-Oriented Reliable Multicast;

   o  PEP: Performance Enhancing Proxy [RFC3135] - a typical PEP for
      satellite communications include compression, caching and TCP
      acceleration;

   o  PLFRAME: Physical Layer FRAME - modulated version of a BBFRAME
      with additional information (e.g., related to synchronization);

   o  QEF: Quasi-Error-Free;

   o  QoE: Quality-of-Experience;

   o  QoS: Quality-of-Service;

   o  SAT: SATellite;

   o  SATCOM: generic term related to all kinds of SATellite
      COMmunication systems;

   o  SPC: Single-Path Coding;

   o  VNF: Virtual Network Function.

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7.  Acknowledgements

   Many thanks to John Border, Stuart Card, Tomaso de Cola, Vincent
   Roca, Lloyd Wood and Marie-Jose Montpetit for their help in writing
   this document.

8.  IANA Considerations

   This memo includes no request to IANA.

9.  Security Considerations

   Security considerations are inherent to any access network, and in
   particular SATCOM systems.  The use of FEC or Network Coding in
   SATCOM also comes with risks (e.g., a single corrupted redundant
   packet may propagate to several flows when they are protected
   together in an Inter-Flow coding approach, see section Section 3).
   However, this is not specific to the SATCOM use-case and this
   document does not further elaborate on it.

10.  Informative References

   [ASMS2010]
              De Cola, T. and et. al., "Demonstration at opening session
              of ASMS 2010", Advanced Satellite Multimedia Systems
              (ASMS) Conference , 2010.

   [CCSDS-131.5-O-1]
              "Erasure correcting codes for use in near-earth and deep-
              space communications", CCSDS Experimental
              specification 131.5-0-1, 2014.

   [ETSITR2017]
              "Satellite Earth Stations and Systems (SES); Multi-link
              routing scheme in hybrid access network with heterogeneous
              links", ETSI TR 103 351, 2017.

   [I-D.chin-nfvrg-cloud-5g-core-structure-yang]
              Chen, C. and Z. Pan, "Yang Data Model for Cloud Native 5G
              Core structure", draft-chin-nfvrg-cloud-5g-core-structure-
              yang-00 (work in progress), December 2017.

   [I-D.vazquez-nfvrg-netcod-function-virtualization]
              Vazquez-Castro, M., Do-Duy, T., Romano, S., and A. Tulino,
              "Network Coding Function Virtualization", draft-vazquez-
              nfvrg-netcod-function-virtualization-02 (work in
              progress), November 2017.

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   [RFC3135]  Border, J., Kojo, M., Griner, J., Montenegro, G., and Z.
              Shelby, "Performance Enhancing Proxies Intended to
              Mitigate Link-Related Degradations", RFC 3135,
              DOI 10.17487/RFC3135, June 2001,
              <https://www.rfc-editor.org/info/rfc3135>.

   [RFC4838]  Cerf, V., Burleigh, S., Hooke, A., Torgerson, L., Durst,
              R., Scott, K., Fall, K., and H. Weiss, "Delay-Tolerant
              Networking Architecture", RFC 4838, DOI 10.17487/RFC4838,
              April 2007, <https://www.rfc-editor.org/info/rfc4838>.

   [RFC5740]  Adamson, B., Bormann, C., Handley, M., and J. Macker,
              "NACK-Oriented Reliable Multicast (NORM) Transport
              Protocol", RFC 5740, DOI 10.17487/RFC5740, November 2009,
              <https://www.rfc-editor.org/info/rfc5740>.

   [RFC6726]  Paila, T., Walsh, R., Luby, M., Roca, V., and R. Lehtonen,
              "FLUTE - File Delivery over Unidirectional Transport",
              RFC 6726, DOI 10.17487/RFC6726, November 2012,
              <https://www.rfc-editor.org/info/rfc6726>.

   [RFC8406]  Adamson, B., Adjih, C., Bilbao, J., Firoiu, V., Fitzek,
              F., Ghanem, S., Lochin, E., Masucci, A., Montpetit, M-J.,
              Pedersen, M., Peralta, G., Roca, V., Ed., Saxena, P., and
              S. Sivakumar, "Taxonomy of Coding Techniques for Efficient
              Network Communications", RFC 8406, DOI 10.17487/RFC8406,
              June 2018, <https://www.rfc-editor.org/info/rfc8406>.

   [SAT2017]  Ahmed, T., Dubois, E., Dupe, JB., Ferrus, R., Gelard, P.,
              and N. Kuhn, "Software-defined satellite cloud RAN",
              International Journal on Satellite Communnications and
              Networking vol. 36 - https://doi.org/10.1002/sat.1206,
              2017.

   [SHINE]    Pietro Romano, S. and et. al., "Secure Hybrid In Network
              caching Environment (SHINE) ESA project", ESA project ,
              2017 on-going.

   [THAI15]   Thai, T., Chaganti, V., Lochin, E., Lacan, J., Dubois, E.,
              and P. Gelard, "Enabling E2E reliable communications with
              adaptive re-encoding over delay tolerant networks",
              Proceedings of the IEEE International Conference on
              Communications http://dx.doi.org/10.1109/ICC.2015.7248441,
              June 2015.

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Authors' Addresses

   Nicolas Kuhn (editor)
   CNES
   18 Avenue Edouard Belin
   Toulouse  31400
   France

   Email: nicolas.kuhn@cnes.fr

   Emmanuel Lochin (editor)
   ISAE-SUPAERO
   10 Avenue Edouard Belin
   Toulouse  31400
   France

   Email: emmanuel.lochin@isae-supaero.fr

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