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Lochin, Ed. 5 Expires: June 13, 2020 ISAE-SUPAERO 6 December 11, 2019 8 Network coding for satellite systems 9 draft-irtf-nwcrg-network-coding-satellites-09 11 Abstract 13 This document is the product of the Coding for Efficient Network 14 Communications Research Group (NWCRG). It conforms to the directions 15 found in the NWCRG taxonomy [RFC8406]. Thus, the scope of the 16 document is network coding as a linear combination of packets in and 17 above the network layer. Physical and MAC layer coding are beyond 18 the scope of the document. The draft focuses on a multi-gateway 19 satellite system and identifies the use-cases where network coding 20 provides significant performance improvements. The objective is to 21 contribute to a larger deployment of network coding techniques in 22 SATCOM to complement already implemented loss recovery mechanisms. 23 The draft also identifies open research issues related to the 24 deployment of network coding in SATCOM systems. 26 Status of This Memo 28 This Internet-Draft is submitted in full conformance with the 29 provisions of BCP 78 and BCP 79. 31 Internet-Drafts are working documents of the Internet Engineering 32 Task Force (IETF). Note that other groups may also distribute 33 working documents as Internet-Drafts. The list of current Internet- 34 Drafts is at https://datatracker.ietf.org/drafts/current/. 36 Internet-Drafts are draft documents valid for a maximum of six months 37 and may be updated, replaced, or obsoleted by other documents at any 38 time. It is inappropriate to use Internet-Drafts as reference 39 material or to cite them other than as "work in progress." 41 This Internet-Draft will expire on June 13, 2020. 43 Copyright Notice 45 Copyright (c) 2019 IETF Trust and the persons identified as the 46 document authors. All rights reserved. 48 This document is subject to BCP 78 and the IETF Trust's Legal 49 Provisions Relating to IETF Documents 50 (https://trustee.ietf.org/license-info) in effect on the date of 51 publication of this document. Please review these documents 52 carefully, as they describe your rights and restrictions with respect 53 to this document. Code Components extracted from this document must 54 include Simplified BSD License text as described in Section 4.e of 55 the Trust Legal Provisions and are provided without warranty as 56 described in the Simplified BSD License. 58 Table of Contents 60 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 61 2. A Note on Satellite Networks Topology . . . . . . . . . . . . 3 62 3. Use-cases for Improving SATCOM System Performance Using 63 Network Coding . . . . . . . . . . . . . . . . . . . . . . . 5 64 3.1. Two-way Relay Channel Mode . . . . . . . . . . . . . . . 5 65 3.2. Reliable Multicast . . . . . . . . . . . . . . . . . . . 5 66 3.3. Hybrid Access . . . . . . . . . . . . . . . . . . . . . . 6 67 3.4. LAN Packet Losses . . . . . . . . . . . . . . . . . . . . 7 68 3.5. Varying Channel Conditions . . . . . . . . . . . . . . . 8 69 3.6. Improving Gateway Handover . . . . . . . . . . . . . . . 8 70 4. Research Challenges . . . . . . . . . . . . . . . . . . . . . 9 71 4.1. Joint-use of Network Coding and Congestion Control in 72 SATCOM Systems . . . . . . . . . . . . . . . . . . . . . 9 73 4.2. Efficient Use of Satellite Resources . . . . . . . . . . 10 74 4.3. Interaction with Virtualized Satellite Gateways and 75 Terminals . . . . . . . . . . . . . . . . . . . . . . . . 10 76 4.4. Delay/Disruption Tolerant Networks . . . . . . . . . . . 10 77 5. Conclusion . . . . . . . . . . . . . . . . . . . . . . . . . 11 78 6. Glossary . . . . . . . . . . . . . . . . . . . . . . . . . . 11 79 7. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 13 80 8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 13 81 9. Security Considerations . . . . . . . . . . . . . . . . . . . 13 82 10. Informative References . . . . . . . . . . . . . . . . . . . 13 83 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 15 85 1. Introduction 87 This document is the product of and represents the collaborative work 88 and consensus of the Coding for Efficient Network Communications 89 Research Group (NWCRG); while it is not an IETF product and not a 90 standard it intends to inform the SATCOM and Internet research 91 communities about recent developments in Network Coding. A glossary 92 is proposed in Section 6 to clarify the terminology use throughout 93 the document. 95 As will be shown in this draft, the implementation of network coding 96 techniques above the network layer of the ISO model, at application 97 or transport layers, offers an opportunity for improving the end-to- 98 end performance of SATCOM systems. While physical- and link-layer 99 coding error protection is usually enough to provide Quasi-Error Free 100 transmission thus minimizing packet loss, when the physical and link 101 layers coding fail or that residual errors create packet losses that 102 greatly interfere with Internet protocols, retransmissions add 103 significant delays because especially in geostationary system with 104 over 0.7 second round-trip delays. Hence the use of network coding 105 at the upper layers can improve the quality of service in SATCOM 106 subnetworks and eventually favorably impact the experience of end 107 users. 109 While there is an active research Community working on network coding 110 techniques above the network layer in general and in SATCOM in 111 particular, not much of this work made it to commercial systems in 112 the satellite industry. In this context, this document aims at 113 identifying opportunities for further usage of network coding in 114 commercial SATCOM networks. 116 The notation used in this document is based on the NWCRG taxonomy 117 [RFC8406]: 119 o Channel and link error correcting codes are considered part of the 120 PHY layer error protection and are out of the scope of this 121 document. 123 o FEC (also called Application-Level FEC) operates in and above the 124 network layer and targets packet loss recovery. 126 o This document considers only coding (or coding techniques or 127 coding schemes) that use a linear combination of packets and 128 excludes for example content coding (e.g., to compress a video 129 flow) or other non-linear operation. 131 2. A Note on Satellite Networks Topology 133 There are multiple SATCOM systems, for example broadcast TV, point to 134 point communication or IoT and monitoring. Therefore, depending on 135 the purpose of the system, the associated ground segments 136 architecture will be different. This section focuses on a satellite 137 system that follows the ETSI DVB standards to provide broadband 138 Internet access via ground-based gateways. One must note that the 139 overall data capacity of one satellite may be higher than the 140 capacity that one single gateway support. Hence, there are usually 141 multiple gateways for one unique satellite platform. 143 In this context, Figure 1 shows an example of a multi-gateway 144 satellite system. More information on a generic SATCOM ground 145 segment architecture for bidirectional Internet access can be found 146 in [SAT2017]. 148 +--------------------------+ 149 | application servers | 150 | (data, coding, multicast)| 151 +--------------------------+ 152 | ... | 153 ----------------------------------- 154 | | | | | | 155 +--------------------+ +--------------------+ 156 | network function | | network function | 157 |(firewall, PEP, etc)| |(firewall, PEP, etc)| 158 +--------------------+ +--------------------+ 159 | ... | IP packets | ... | 160 --- 161 +------------------+ +------------------+ | 162 | access gateway | | access gateway | | 163 +------------------+ +------------------+ | 164 | BBFRAME | | gateway 165 +------------------+ +------------------+ | 166 | physical gateway | | physical gateway | | 167 +------------------+ +------------------+ | 168 --- 169 | PLFRAME | 170 +------------------+ +------------------+ 171 | outdoor unit | | outdoor unit | 172 +------------------+ +------------------+ 173 | satellite link | 174 +------------------+ +------------------+ 175 | outdoor unit | | outdoor unit | 176 +------------------+ +------------------+ 177 | | 178 +------------------+ +------------------+ 179 | sat terminals | | sat terminals | 180 +------------------+ +------------------+ 181 | | | | 182 +----------+ | +----------+ | 183 |end user 1| | |end user 3| | 184 +----------+ | +----------+ | 185 +----------+ +----------+ 186 |end user 2| |end user 4| 187 +----------+ +----------+ 189 Figure 1: Data plane functions in a generic satellite multi-gateway 190 system. More details can be found in DVB standard documents. 192 3. Use-cases for Improving SATCOM System Performance Using Network 193 Coding 195 This section details use-cases where network coding techniques could 196 improve SATCOM system performance. 198 3.1. Two-way Relay Channel Mode 200 This use-case considers two-way communication between end-users, 201 through a satellite link as seen in Figure 2. 203 Satellite terminal A sends a packet flow A and satellite terminal B 204 sends a packet flow B to a coding server. The coding server then 205 sends a combination of both flows instead of each individual flows. 206 This results in non-negligible capacity savings that has been 207 demonstrated in the past [ASMS2010]. In the example, a dedicated 208 coding server is introduced (note that its location could be 209 different based on deployment use-case). The network coding 210 operations could also be done at the satellite level, although this 211 would require a lot of computational resource on-board and may not be 212 supported by today's satellites. 214 -X}- : traffic from satellite terminal X to the server 215 ={X+Y= : traffic from X and Y combined sent from 216 the server to terminals X and Y 218 +-----------+ +-----+ 219 |Sat term A |--A}-+ | | 220 +-----------+ | | | +---------+ +------+ 221 ^^ +--| |--A}--| |--A}--|Coding| 222 || | SAT |--B}--| Gateway |--B}--|Server| 223 ===={A+B=========| |={A+B=| |={A+B=| | 224 || | | +---------+ +------+ 225 vv +--| | 226 +-----------+ | | | 227 |Sat term B |--B}-+ | | 228 +-----------+ +-----+ 230 Figure 2: Network Architecture for Two-way Relay Channel using NC 232 3.2. Reliable Multicast 234 The use of multicast servers is one way to better utilize a satellite 235 broadcast capabilities. Multicast is proposed in the SHINE ESA 236 project [I-D.vazquez-nfvrg-netcod-function-virtualization] [SHINE]. 237 This use-case considers adding redundancy to a multicast flow 238 depending on what has been received by different end-users, resulting 239 in non-negligible savings of the scarce SATCOM resources. This 240 scenario is shown in Figure 3. 242 -Li}- : packet indicating the loss of packet i of a multicast flow M 243 ={M== : multicast flow including the missing packets 245 +-----------+ +-----+ 246 |Sat term A |-Li}-+ | | 247 +-----------+ | | | +---------+ +------+ 248 ^^ +-| |-Li}--| | |Multi | 249 || | SAT |-Lj}--| Gateway |--|Cast | 250 ===={M==========| |={M===| | |Server| 251 || | | +---------+ +------+ 252 vv +-| | 253 +-----------+ | | | 254 |Sat term B |-Lj}-+ | | 255 +-----------+ +-----+ 257 Figure 3: Network Architecture for a Reliable Multicast using NC 259 A multicast flow (M) is forwarded to both satellite terminals A and 260 B. However packet Ni (respectively Nj) gets lost at terminal A 261 (respectively B), and terminal A (respectively B) returns a negative 262 acknowledgment Li (respectively Lj), indicating that the packet is 263 missing. Using NC, either the access gateway or the multicast server 264 can include a repair packet (rather than the individual Ni and Nj 265 packets) in the multicast flow to let both terminals recover from 266 losses. 268 This could also be achieved by using other multicast or broadcast 269 systems, such as NACK-Oriented Reliable Multicast (NORM) [RFC5740] or 270 File Delivery over Unidirectional Transport (FLUTE) [RFC6726]. Both 271 NORM and FLUTE are limited to block coding, none of them supporting 272 more flexible sliding window encoding schemes that allow decoding 273 before receiving the whole block an added delay benefit [RFC8406]. 275 3.3. Hybrid Access 277 This use-case considers improving multiple path communications with 278 network coding at the transport layer (see Figure 4). This use-case 279 is inspired by the Broadband Access via Integrated Terrestrial 280 Satellite Systems (BATS) project and has been published as an ETSI 281 Technical Report [ETSITR2017]. 283 To cope with packet loss (due to either end-user mobility or 284 physical-layer residual errors), network coding can be introduced 285 both at the CPE and at the concentrator. Apart from packet losses, 286 other gains from this approach include a better tolerance to out-of- 287 order packet delivery which occur when exploited links exhibit high 288 asymmetry in terms of RTT. Depending on the ground architecture 289 [I-D.chin-nfvrg-cloud-5g-core-structure-yang] [SAT2017], some ground 290 equipment might be hosting both SATCOM and cellular network 291 functionality. 293 -{}- : bidirectional link 295 +---+ +--------------+ 296 +-{}-|SAT|-{}-|BACKBONE | 297 +----+ +---+ | +---+ |+------------+| 298 |End |-{}-|CPE|-{}-| ||CONCENTRATOR|| 299 |User| +---+ | +---+ |+------------+| +-----------+ 300 +----+ |-{}-|DSL|-{}-| |-{}-|Application| 301 | +---+ | | |Server | 302 | | | +-----------+ 303 | +---+ | | 304 +-{}-|LTE|-{}-+--------------+ 305 +---+ 307 Figure 4: Network Architecture for a Hybrid Access Using Network 308 Coding 310 3.4. LAN Packet Losses 312 This use-case considers using network coding in the scenario where a 313 lossy WIFI link is used to connect to the SATCOM network. When 314 encrypted end-to-end applications based on UDP are used, a PEP cannot 315 operate hence other mechanism need to be used. The WIFI packet 316 losses will result in an end-to-end retransmission that will harm the 317 end-user quality of experience and poorly utilize SATCOM bottleneck 318 resource for non-revenue generating traffic. In this use-case, 319 adding network coding techniques will prevent the end-to-end 320 retransmission from occurring since the packet losses will be 321 recovered. 323 The architecture is shown in Figure 5. 325 -{}- : bidirectional link 326 -''- : Wi-Fi link 327 C : where network coding techniques could be introduced 329 +----+ +---------+ +---+ +--------+ +-------+ +--------+ 330 |End | |Satellite| |SAT| |Physical| |Access | |Network | 331 |user|-''-|Terminal |-{}-| |-{}-|Gateway |-{}-|Gateway|-{}-|Function| 332 +----+ +---------+ +---+ +--------+ +-------+ +--------+ 333 C C C C 335 Figure 5: Network Architecture for dealing with LAN Losses 337 3.5. Varying Channel Conditions 339 This use-case considers the usage of network coding to cope with sub 340 second physical channel condition changes where the physical-layer 341 mechanisms (Adaptive Coding and Modulation (ACM)) may not adapt the 342 modulation and error-correction coding in time: the residual errors 343 lead to higher layer packet losses that can be recovered with network 344 coding. This use-case is mostly relevant when mobile users are 345 considered or when the satellite frequency band introduces quick 346 changes in channel condition (Q/V bands, Ka band, etc.). Depending 347 on the use-case (e.g., very high frequency bands, mobile users) or 348 depending on the deployment use-cases (e.g., performance of the 349 network between each individual data block), the relevance of adding 350 network coding is different. 352 The system architecture is shown in Figure 6. 354 -{}- : bidirectional link 355 C : where network coding techniques could be introduced 357 +---------+ +---+ +--------+ +-------+ +--------+ 358 |Satellite| |SAT| |Physical| |Access | |Network | 359 |Terminal |-{}-| |-{}-|Gateway |-{}-|Gateway|-{}-|Function| 360 +---------+ +---+ +--------+ +-------+ +--------+ 361 C C C C 363 Figure 6: Network Architecture for dealing with Varying Link 364 Characteristics 366 3.6. Improving Gateway Handover 368 This use-case considers the recovery of packets that may be lost 369 during gateway handover. Whether for off-loading a given equipment 370 or because the transmission quality differs from gateway to gateway, 371 switching the transmission gateway may be beneficial. However, 372 packet losses can occur if the gateways are not properly synchronized 373 or if the algorithm used to trigger gateway handover is not properly 374 tuned. During these critical phases, network coding can be added to 375 improve the reliability of the transmission and allow a seamless 376 gateway handover. 378 Figure 7 illustrates this use-case. 380 -{}- : bidirectional link 381 ! : management interface 382 C : where network coding techniques could be introduced 383 C C 384 +--------+ +-------+ +--------+ 385 |Physical| |Access | |Network | 386 +-{}-|gateway |-{}-|gateway|-{}-|function| 387 | +--------+ +-------+ +--------+ 388 | ! ! 389 +---------+ +---+ +---------------+ 390 |Satellite| |SAT| | Control plane | 391 |Terminal |-{}-| | | manager | 392 +---------+ +---+ +---------------+ 393 | ! ! 394 | +--------+ +-------+ +--------+ 395 +-{}-|Physical|-{}-|Access |-{}-|Network | 396 |gateway | |gateway| |function| 397 +--------+ +-------+ +--------+ 398 C C 400 Figure 7: Network Architecture for dealing with Gateway Handover 402 4. Research Challenges 404 This section proposes a few potential approaches to introduce and use 405 network coding in SATCOM systems. 407 4.1. Joint-use of Network Coding and Congestion Control in SATCOM 408 Systems 410 Many SATCOM systems typically use Performance Enhancing Proxy (PEP) 411 RFC 3135 [RFC3135]. PEPs usually split end-to-end connections and 412 forward transport or application layer packets to the satellite 413 baseband gateway that deals with layer-2 and layer-1 encapsulation. 414 PEPs contribute to mitigate congestion in a SATCOM systems by 415 limiting the impact of long delays on Internet protocols. A PEP 416 mechanism could also include network coding operation and thus 417 support the use-cases that have been discussed in the Section 3 of 418 this document. 420 Deploying network coding in the PEP could be relevant and be 421 independent from the specifics of a SATCOM link. This however leads 422 to research questions dealing with the potential interaction between 423 network coding and congestion control. 425 4.2. Efficient Use of Satellite Resources 427 There is a recurrent trade-off in SATCOM systems: how much overhead 428 from redundant reliability packets can be introduced to guarantee a 429 better end-user QoE while optimizing capacity usage ? At which layer 430 this supplementary redundancy should be added ? 432 This problem has been tackled in the past by the deployment of 433 physical-layer error-correction codes, but there remains questions on 434 adapting the coding overhead and added delay for, e.g., the quickly 435 varying channel conditions use-case where ACM may not be reacting 436 quickly enough as was discussed on the previous section. 438 4.3. Interaction with Virtualized Satellite Gateways and Terminals 440 In the emerging virtualized network infrastructure, network coding 441 could be easily deployed as a VNF. The next generation of SATCOM 442 ground segments will rely on a virtualized environment to integrate 443 to terrestrial networks. This trend towards NFV is also central to 444 5G and next generation cellular networks, making this research 445 applicable to other deployment scenarios 446 [I-D.chin-nfvrg-cloud-5g-core-structure-yang]. As one example, the 447 network coding VNF deployment in a virtualized environment has been 448 presented in [I-D.vazquez-nfvrg-netcod-function-virtualization]. 450 A research challenge would be the optimization of the NFV service 451 function chaining, considering a virtualized infrastructure and other 452 SATCOM specific functions, in order to guarantee efficient radio-link 453 usage and provide easy-to-deploy SATCOM services. Moreover, another 454 challenge related to a virtualized SATCOM equipment is the management 455 of limited buffered capacities in large gateways. 457 4.4. Delay/Disruption Tolerant Networks 459 Communications among deep-space platforms and terrestrial gateways 460 can be a challenge. Reliable end-to-end (E2E) communications over 461 such paths must cope with very long delays and frequent link 462 disruptions; indeed, E2E connectivity may be available only 463 intermittently. Delay/Disruption Tolerant Networking [RFC4838] is a 464 solution to enable reliable internetworking space communications 465 where both standard ad-hoc routing and E2E Internet protocols cannot 466 be used. Moreover, DTN can also be seen as an alternative solution 467 to transfer data between a central PEP and a remote PEP. 469 Network Coding enables E2E reliable communications over a DTN with 470 potential adaptive re-encoding, as proposed in [THAI15]. Here, the 471 use-cases proposed in Section 3.5 would legitimize the usage of 472 network coding within the DTN stack to improve the physical channel 473 utilization and minimize the effects of the E2E transmission delays. 474 In this context, the use of packet erasure coding techniques inside a 475 Consultative Committee for Space Data Systems (CCSDS) architecture 476 has been specified in [CCSDS-131.5-O-1]. One research challenge 477 remains on how such network coding can be integrated in the IETF DTN 478 stack. 480 5. Conclusion 482 This document introduces some wide-scale network coding techniques 483 opportunities in satellite telecommunications systems. 485 Even though this document focuses on satellite systems, it is worth 486 pointing out that some scenarios proposed here may be relevant to 487 other wireless telecommunication systems. As one example, the 488 generic architecture proposed in Figure 1 may be mapped onto cellular 489 networks as follows: the 'network function' block gathers some of the 490 functions of the Evolved Packet Core subsystem, while the 'access 491 gateway' and 'physical gateway' blocks gather the same type of 492 functions as the Universal Mobile Terrestrial Radio Access Network. 493 This mapping extends the opportunities identified in this draft since 494 they may also be relevant for cellular networks. 496 6. Glossary 498 The glossary of this memo extends the glossary of the taxonomy 499 document [RFC8406] as follows: 501 o ACM : Adaptive Coding and Modulation; 503 o BBFRAME: Base-Band FRAME - satellite communication layer 2 504 encapsulation work as follows: (1) each layer 3 packet is 505 encapsulated with a Generic Stream Encapsulation (GSE) mechanism, 506 (2) GSE packets are gathered to create BBFRAMEs, (3) BBFRAMEs 507 contain information related to how they have to be modulated (4) 508 BBFRAMEs are forwarded to the physical-layer; 510 o CPE: Customer Premises Equipment; 512 o COM: COMmunication; 514 o DSL: Digital Subscriber Line; 516 o DTN: Delay/Disruption Tolerant Network; 517 o DVB: Digital Video Broadcasting; 519 o E2E: End-to-end; 521 o ETSI: European Telecommunications Standards Institute; 523 o FEC: Forward Erasure Correction; 525 o FLUTE: File Delivery over Unidirectional Transport; 527 o IntraF: Intra-Flow Coding; 529 o InterF: Inter-Flow Coding; 531 o IoT: Internet of Things; 533 o LTE: Long Term Evolution; 535 o MPC: Multi-Path Coding; 537 o NC: Network Coding; 539 o NFV: Network Function Virtualization; 541 o NORM: NACK-Oriented Reliable Multicast; 543 o PEP: Performance Enhancing Proxy [RFC3135] - a typical PEP for 544 satellite communications include compression, caching and TCP 545 acceleration; 547 o PLFRAME: Physical Layer FRAME - modulated version of a BBFRAME 548 with additional information (e.g., related to synchronization); 550 o QEF: Quasi-Error-Free; 552 o QoE: Quality-of-Experience; 554 o QoS: Quality-of-Service; 556 o SAT: SATellite; 558 o SATCOM: generic term related to all kinds of SATellite 559 COMmunication systems; 561 o SPC: Single-Path Coding; 563 o VNF: Virtual Network Function. 565 7. Acknowledgements 567 Many thanks to John Border, Stuart Card, Tomaso de Cola, Vincent 568 Roca, Lloyd Wood and Marie-Jose Montpetit for their help in writing 569 this document. 571 8. IANA Considerations 573 This memo includes no request to IANA. 575 9. Security Considerations 577 Security considerations are inherent to any access network, and in 578 particular SATCOM systems. The use of FEC or Network Coding in 579 SATCOM also comes with risks (e.g., a single corrupted redundant 580 packet may propagate to several flows when they are protected 581 together in an Inter-Flow coding approach, see section Section 3). 582 However, this is not specific to the SATCOM use-case and this 583 document does not further elaborate on it. 585 10. Informative References 587 [ASMS2010] 588 De Cola, T. and et. al., "Demonstration at opening session 589 of ASMS 2010", Advanced Satellite Multimedia Systems 590 (ASMS) Conference , 2010. 592 [CCSDS-131.5-O-1] 593 "Erasure correcting codes for use in near-earth and deep- 594 space communications", CCSDS Experimental 595 specification 131.5-0-1, 2014. 597 [ETSITR2017] 598 "Satellite Earth Stations and Systems (SES); Multi-link 599 routing scheme in hybrid access network with heterogeneous 600 links", ETSI TR 103 351, 2017. 602 [I-D.chin-nfvrg-cloud-5g-core-structure-yang] 603 Chen, C. and Z. Pan, "Yang Data Model for Cloud Native 5G 604 Core structure", draft-chin-nfvrg-cloud-5g-core-structure- 605 yang-00 (work in progress), December 2017. 607 [I-D.vazquez-nfvrg-netcod-function-virtualization] 608 Vazquez-Castro, M., Do-Duy, T., Romano, S., and A. Tulino, 609 "Network Coding Function Virtualization", draft-vazquez- 610 nfvrg-netcod-function-virtualization-02 (work in 611 progress), November 2017. 613 [RFC3135] Border, J., Kojo, M., Griner, J., Montenegro, G., and Z. 614 Shelby, "Performance Enhancing Proxies Intended to 615 Mitigate Link-Related Degradations", RFC 3135, 616 DOI 10.17487/RFC3135, June 2001, 617 . 619 [RFC4838] Cerf, V., Burleigh, S., Hooke, A., Torgerson, L., Durst, 620 R., Scott, K., Fall, K., and H. Weiss, "Delay-Tolerant 621 Networking Architecture", RFC 4838, DOI 10.17487/RFC4838, 622 April 2007, . 624 [RFC5740] Adamson, B., Bormann, C., Handley, M., and J. Macker, 625 "NACK-Oriented Reliable Multicast (NORM) Transport 626 Protocol", RFC 5740, DOI 10.17487/RFC5740, November 2009, 627 . 629 [RFC6726] Paila, T., Walsh, R., Luby, M., Roca, V., and R. Lehtonen, 630 "FLUTE - File Delivery over Unidirectional Transport", 631 RFC 6726, DOI 10.17487/RFC6726, November 2012, 632 . 634 [RFC8406] Adamson, B., Adjih, C., Bilbao, J., Firoiu, V., Fitzek, 635 F., Ghanem, S., Lochin, E., Masucci, A., Montpetit, M-J., 636 Pedersen, M., Peralta, G., Roca, V., Ed., Saxena, P., and 637 S. Sivakumar, "Taxonomy of Coding Techniques for Efficient 638 Network Communications", RFC 8406, DOI 10.17487/RFC8406, 639 June 2018, . 641 [SAT2017] Ahmed, T., Dubois, E., Dupe, JB., Ferrus, R., Gelard, P., 642 and N. Kuhn, "Software-defined satellite cloud RAN", 643 International Journal on Satellite Communnications and 644 Networking vol. 36 - https://doi.org/10.1002/sat.1206, 645 2017. 647 [SHINE] Pietro Romano, S. and et. al., "Secure Hybrid In Network 648 caching Environment (SHINE) ESA project", ESA project , 649 2017 on-going. 651 [THAI15] Thai, T., Chaganti, V., Lochin, E., Lacan, J., Dubois, E., 652 and P. Gelard, "Enabling E2E reliable communications with 653 adaptive re-encoding over delay tolerant networks", 654 Proceedings of the IEEE International Conference on 655 Communications http://dx.doi.org/10.1109/ICC.2015.7248441, 656 June 2015. 658 Authors' Addresses 660 Nicolas Kuhn (editor) 661 CNES 662 18 Avenue Edouard Belin 663 Toulouse 31400 664 France 666 Email: nicolas.kuhn@cnes.fr 668 Emmanuel Lochin (editor) 669 ISAE-SUPAERO 670 10 Avenue Edouard Belin 671 Toulouse 31400 672 France 674 Email: emmanuel.lochin@isae-supaero.fr