Internet Engineering Task Force N. Kuhn, Ed. Internet-Draft CNES Intended status: Informational E. Lochin, Ed. Expires: August 29, 2018 ISAE-SUPAERO February 25, 2018 Network coding and satellites draft-kuhn-nwcrg-network-coding-satellites-02 Abstract This memo presents the current deployment of network coding in some satellite telecommunications systems along with a discussion on the multiple opportunities to introduce these techniques at a wider scale. 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 Task Force (IETF). Note that other groups may also distribute working documents as Internet-Drafts. The list of current Internet- Drafts is at https://datatracker.ietf.org/drafts/current/. Internet-Drafts are draft documents valid for a maximum of six months and may be updated, replaced, or obsoleted by other documents at any time. It is inappropriate to use Internet-Drafts as reference material or to cite them other than as "work in progress." This Internet-Draft will expire on August 29, 2018. Copyright Notice Copyright (c) 2018 IETF Trust and the persons identified as the document authors. All rights reserved. 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. Kuhn & Lochin Expires August 29, 2018 [Page 1] Internet-Draft Network coding and satellites February 2018 Table of Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 1.1. Glossary . . . . . . . . . . . . . . . . . . . . . . . . 2 1.2. Requirements Language . . . . . . . . . . . . . . . . . . 3 2. A note on satellite topology . . . . . . . . . . . . . . . . 3 3. Status of network coding in actually deployed satellite systems . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 4. Opportunities for more network coding in satellite systems . 5 5. Details on the use cases . . . . . . . . . . . . . . . . . . 6 5.1. Two way relay channel mode . . . . . . . . . . . . . . . 6 5.2. Reliable multi-cast . . . . . . . . . . . . . . . . . . . 7 5.3. Hybrid access . . . . . . . . . . . . . . . . . . . . . . 7 5.4. Delay Tolerant Network architecture . . . . . . . . . . . 8 5.5. Dealing with varying capacity . . . . . . . . . . . . . . 8 6. Discussion on the deployability . . . . . . . . . . . . . . . 8 7. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 9 8. Contributors . . . . . . . . . . . . . . . . . . . . . . . . 9 9. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 9 10. Security Considerations . . . . . . . . . . . . . . . . . . . 9 11. References . . . . . . . . . . . . . . . . . . . . . . . . . 9 11.1. Normative References . . . . . . . . . . . . . . . . . . 9 11.2. Informative References . . . . . . . . . . . . . . . . . 10 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 10 1. Introduction Network coding schemes are inherent part of the satellite systems as the physical layer requires specific robustness to guarantee an efficient usage of the expensive radio resource. Further exploiting these schemes is an opportunity for a better end-user experience along with a better exploitation of the scarce resource. In this context, this memo aims at: o summing up the current deployment of network coding schemes over LEO and GEO satellite systems; o identifying opportunities for further usage of network coding in these systems. 1.1. Glossary The glossary of this memo is related to the network coding taxonomy document [I-D.irtf-nwcrg-network-coding-taxonomy]. The glossary is extended as follows: Kuhn & Lochin Expires August 29, 2018 [Page 2] Internet-Draft Network coding and satellites February 2018 o BBFRAME: Base-Band FRAME; o PLFRAME: Physical Layer FRAME; o PEP: Performance Enhanced Proxy; o SATCOM: SATellite COMmunications; o EPC: Evolved Packet Core; o UMTRAN: Universal Mobile Terrestrial Radio Access Network; o QoS: Quality-of-Service; o QoE: Quality-of-Experience; o VNF: Virtualized Network Function; o CPE: Customer Premise Equipment; o DTN: Delay Tolerant Network. 1.2. Requirements Language The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in RFC 2119 [RFC2119]. 2. A note on satellite topology The objective of this section is to provide both a generic description of the components composing a generic satellite system and their interaction. It provides a high level description of a multi-gateway satellites network. There exist multiple SATCOM systems, such as those dedicated to broadcasting TV or to IoT applications: depending on the purpose of the SATCOM system, ground segments are specific. This memo lays on SATCOM systems dedicated to Internet access that follows the DVB-S2/RCS2 standards. In this context, Figure 1 shows an example of a multigateway satellite system. More details on a generic SATCOM ground segment architecture for a bi-directional Internet access can be found in [SAT2017]. This architecture may be mapped to cellular networks as follows: the 'network function' block gather 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 Kuhn & Lochin Expires August 29, 2018 [Page 3] Internet-Draft Network coding and satellites February 2018 extends the opportunities identified in this draft since they may be also relevant for cellular networks. It is worth noting that some functional blocks aggregate the traffic coming from multiple users, allowing the deployment of network coding schemes. +---------------------+ | Application servers | +---------------------+ | | | | | | ----------------------------------- v v v v v v +------------------+ +------------------+ | network function | | network function | | (firewall, PEP) | | (firewall, PEP) | +------------------+ +------------------+ | | | | | | IP packets | | v v v v +------------------+ +------------------+ | access gateway | | access gateway | +------------------+ +------------------+ | | | BBFrames | v v +------------------+ +------------------+ | physical gateway | | physical gateway | +------------------+ +------------------+ | | | PLFrames | v v +------------------+ +------------------+ | outdoor unit | | outdoor unit | +------------------+ +------------------+ | | | | | | Satellite link | | v v v v +------------------+ +------------------+ | sat terminals | | sat terminals | +------------------+ +------------------+ Figure 1: Data plane functions in a generic satellite multi-gateway system Kuhn & Lochin Expires August 29, 2018 [Page 4] Internet-Draft Network coding and satellites February 2018 3. Status of network coding in actually deployed satellite systems Figure 2 presents the status of the network coding deployment in satellite systems. The information is based on the taxonomy document [I-D.irtf-nwcrg-network-coding-taxonomy] and the notations are the following: End-to-End Coding (E2E), Network Coding (NC), Intra-Flow Coding (IntraF), Inter-Flow Coding (InterF), Single-Path Coding (SP) and Multi-Path Coding (MP). X1 embodies the source coding that could be used at application level for instance: for video streaming on a broadband access. X2 embodies the physical layer, applied to the PLFRAME, to optimize the satellite capacity usage. Furthermore, at the physical layer and when random accesses are exploited, FEC mechanisms are exploited. +------+-------+---------+---------------+-------+ | | Upper | Middle | Communication layers | | | Appl. | ware | | + +-------+---------+---------------+-------+ | |Source | Network | Packetization | PHY | | |coding | AL-FEC | UDP/IP | layer | +------+-------+---------+---------------+-------+ |E2E | X1 | | | | |NC | | | | | |IntraF| X1 | | | | |InterF| | | | X2 | |SP | X1 | | | X2 | |MP | | | | | +------+-------+---------+---------------+-------+ Figure 2: Network coding and satellite systems 4. Opportunities for more network coding in satellite systems This section extends Section 3 by presenting potential opportunities for the deployment of network coding schemes inside satellite systems. These opportunities are further detailed in Section 5 and listed in this section: 1. Two ways relay channel mode (more details in Section 5.1); 2. Reliable multi-cast (more details in Section 5.2); 3. Hybrid access (more details in Section 5.3); Kuhn & Lochin Expires August 29, 2018 [Page 5] Internet-Draft Network coding and satellites February 2018 4. Delay Tolerant Network architecture (more details in Section 5.4); 5. Dealing with varying capacity (more details in Section 5.5); It is worth noting that these opportunities focus more on the middle ware (e.g. aggregation nodes) and packetization UDP/IP of Figure 2. Indeed, there are already lots of recovery mechanisms at the physical and access layers in currently deployed systems while E2E source coding are done at the application level. In a multigateway SATCOM Internet access, the specific opportunities are more relevant in specific SATCOM components such as the "network function" block or the "access gateway" of Figure 1. 5. Details on the use cases This section details use-cases where network coding schemes could improve the overall performance of a SATCOM system (e.g. considering a more efficient usage of the satellite resource, delivery delay, delivery ratio). 5.1. Two way relay channel mode This use-case considers a two-way communication between end users, through a satellite link. We propose an illustration of this scenario in Figure 3. Satellite terminal A (resp. B) transmits a flow A (resp. B) to a server hosting NC capabilities, which forward a combination of the two flows to both terminals. This results in non-negligible bandwidth saving and has been demonstrated at ASMS 2010 in Cagliari. +------------+ +-----+ +---------+ | Satellite | A | | A | | | Terminal A |-->--| | |->---| | +------+ +------------+ | | |->---| | | | || A+B ->-| SAT | B | Gateway | | | ==================| | | |--|Server| || ->-| | | | | | +------------+ B |>-| |=====| | | | | Satellite |-->--| | | A+B | | +------+ | Terminal B | | | | | +------------+ +-----+ +---------+ Figure 3: Network architecture for two way relay channel with NC Kuhn & Lochin Expires August 29, 2018 [Page 6] Internet-Draft Network coding and satellites February 2018 5.2. Reliable multi-cast This use-case considers adding redundancy to a multi-cast flow depending on what has been received by different end-users, resulting in non-negligible scarce resource saving. We propose an illustration for this scenario in Figure 4. A multi-cast flow (M) is forward to both satellite terminals A and B. On the uplink, terminal A (resp. B) does not acknowledge the packet Ni (resp. Nj) and either the access gateway or the multi-cast server includes the missing packets in the multi-cast flow so that the information transfer is reliable. +------------+ +-----+ +---------+ | Satellite |NACK Ni | |NACK Ni| | | Terminal A |-->--| | |->-----| | +------+ +------------+ | | |->-----| | | | || M ->-| SAT |NACK Nj| | |Multi | ==================| | | Gateway |--|Cast | || ->-| | | | |Server| +------------+ |>-| |=======| | | | | Satellite |-->--| | | M | | +------+ | Terminal B |NACK Nj | | | | +------------+ +-----+ +---------+ Figure 4: Network architecture for a reliable multi-cast with NC 5.3. Hybrid access This use-case considers the use of multiple path management with network coding at the transport level to either increase the reliability or the total bandwidth. We propose an illustration for this scenario in Figure 5. This use-case is inspired from the Broadband Access via Integrated Terrestrial Satellite Systems (BATS) project. The architecture is also discussed in the MPTCP working group [I-D.boucadair-mptcp-dhc]. To cope from packet loss (due to either end-user movements or physical layer impairments), network coding could be introduced in both the CPE and at the concentrator. Kuhn & Lochin Expires August 29, 2018 [Page 7] Internet-Draft Network coding and satellites February 2018 +-------------+ +----------------+ |->| SAT NETWORK |---| BACKBONE | | +-------------+ | +------------+ | +------+ | | |CONCENTRATOR| | | CPE |-->-| +-----+ | +------------+ | +------+ |->| DSL |-----------| | | +-----+ | | | | | | +-----+ | | |->| LTE |-----------| | +-----+ +----------------+ Figure 5: Network architecture for an hybrid access using NC 5.4. Delay Tolerant Network architecture ** EL: ** TBD with bundle layer as a candidate for NC 5.5. Dealing with varying capacity This use-case considers the usage of network coding to overcome cases where the wireless link characteristics quickly change overtime and where the physical layer codes could not be made robust in time. The network coding schemes could be applied at the access gateway or the network function block levels to increase the reliability of the transmission. This use-case is relevant for, e.g. when mobile users are considered or when the chosen band induce a required physical layer coding that may change over time (Q/V bands, Ka band, etc.). +------------+ +-----+ +---------+ +--------+ +---------+ | Satellite | | SAT | | Physical| | Access | | Network | | Terminal |->| |->| gateway |->| gateway|->| function| +------------+ +-----+ +---------+ +--------+ +---------+ Figure 6: Network architecture for dealing with varying link characteristics with NC 6. Discussion on the deployability This section discusses the deployability of the opportunities that are provided in Section 4. SATCOM systems typically feature Proxy-Enhanced-Proxy RFC 3135 [RFC3135] which could be relevant to host network coding mechanisms and thus support the use-cases that have been discussed in Section 5. In particular the discussion on how network coding can be integrated inside a PEP with QoS scheduler has been proposed in RFC 5865 [RFC5865]. Kuhn & Lochin Expires August 29, 2018 [Page 8] Internet-Draft Network coding and satellites February 2018 Related to the foreseen virtualized network infrastructure, the network coding schemes could be proposed as VNF and their deployability enhanced. The architecture for the next generation of SATCOM ground segments would rely on a virtualized environment. This trend can also be seen, making the discussions on the deployability of network coding in SATCOM extendable to other deployment scenarios [I-D.chin-nfvrg-cloud-5g-core-structure-yang]. As one example, the network coding VNF functions deployment in a virtualized environment is presented in [I-D.vazquez-nfvrg-netcod-function-virtualization]. 7. Acknowledgements 8. Contributors Many thanks to 9. IANA Considerations This memo includes no request to IANA. 10. Security Considerations This document, by itself, presents no new privacy nor security issues. 11. References 11.1. Normative References [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, DOI 10.17487/RFC2119, March 1997, . [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, . [RFC5865] Baker, F., Polk, J., and M. Dolly, "A Differentiated Services Code Point (DSCP) for Capacity-Admitted Traffic", RFC 5865, DOI 10.17487/RFC5865, May 2010, . Kuhn & Lochin Expires August 29, 2018 [Page 9] Internet-Draft Network coding and satellites February 2018 11.2. Informative References [I-D.boucadair-mptcp-dhc] Boucadair, M., Jacquenet, C., and T. Reddy, "DHCP Options for Network-Assisted Multipath TCP (MPTCP)", draft- boucadair-mptcp-dhc-08 (work in progress), October 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.irtf-nwcrg-network-coding-taxonomy] Adamson, B., Adjih, C., Bilbao, J., Firoiu, V., Fitzek, F., samah.ghanem@gmail.com, s., Lochin, E., Masucci, A., Montpetit, M., Pedersen, M., Peralta, G., Roca, V., Saxena, P., and S. Sivakumar, "Taxonomy of Coding Techniques for Efficient Network Communications", draft- irtf-nwcrg-network-coding-taxonomy-07 (work in progress), February 2018. [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. [SAT2017] Ahmed, T., Dubois, E., Dupe, JB., Ferrus, R., Gelard, P., and N. Kuhn, "Software-defined satellite cloud RAN", Int. J. Satell. Commun. Network. vol. 36, 2017. Authors' Addresses Nicolas Kuhn (editor) CNES 18 Avenue Edouard Belin Toulouse 31400 France Email: nicolas.kuhn@cnes.fr Kuhn & Lochin Expires August 29, 2018 [Page 10] Internet-Draft Network coding and satellites February 2018 Emmanuel Lochin (editor) ISAE-SUPAERO 10 Avenue Edouard Belin Toulouse 31400 France Email: emmanuel.lochin@isae-supaero.fr Kuhn & Lochin Expires August 29, 2018 [Page 11]