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NFVRG                                               M. A. Vazquez-Castro
Internet-Draft                                                 T. Do-Duy
Intended status: Informational                                       UAB
Expires: May 20, 2018                                      S.  P. Romano
                                                            A. M. Tulino
                                                                   Unina
                                                       November 16, 2017


                 Network Coding Function Virtualization
         draft-vazquez-nfvrg-netcod-function-virtualization-02

Abstract

   This document describes network coding as a network function.  It
   also describes how a network coding function can be virtualized and
   integrated with virtual network functions architectures.  The network
   coding function is not a traditionally implemented network function
   in dedicated hardware as those that have triggered network function
   virtualization.  It refers to a novel network functionality that
   generalizes classic packet-level end-to-end coding.  Classic packet-
   level end-to-end coding helps in the provision of quality of service
   by trading off delay and reliability.  Network coding goes beyond
   that by enabling in-network optimized re-encoding, which can provide
   both throughput gains and diverse network-controlled degrees of
   reliability.  Consequently, a virtualized network coding function can
   serve as a flow engineering tool over virtualized networks (e.g. over
   network slices).

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 May 20, 2018.






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Copyright Notice

   Copyright (c) 2017 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.

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   3
   2.  Conventions used in this document . . . . . . . . . . . . . .   4
   3.  Network coding as a network function  . . . . . . . . . . . .   5
     3.1.  Design domains of the network coding function . . . . . .   6
       3.1.1.  Coding domain . . . . . . . . . . . . . . . . . . . .   6
       3.1.2.  Functional domain . . . . . . . . . . . . . . . . . .   6
       3.1.3.  Protocol domain . . . . . . . . . . . . . . . . . . .   7
     3.2.  Flexible modular design via sets of subfunctions  . . . .   7
       3.2.1.  Coding/Re-encoding/Decoding Functionalities (CRDF)  .   7
       3.2.2.  Flow Engineering Functionalities (FEF)  . . . . . . .   7
       3.2.3.  Physical/Abstraction Functionalities (PAF)  . . . . .   7
   4.  Virtual Network Coding Function . . . . . . . . . . . . . . .   7
     4.1.  Virtualization of flows . . . . . . . . . . . . . . . . .   7
     4.2.  Integration with ETSI NFV architecture  . . . . . . . . .   8
     4.3.  Example . . . . . . . . . . . . . . . . . . . . . . . . .   9
       4.3.1.  The SHINE use case  . . . . . . . . . . . . . . . . .  10
   5.  Conclusions . . . . . . . . . . . . . . . . . . . . . . . . .  14
   6.  Differences with respect to version -01 . . . . . . . . . . .  14
   7.  Acknowledgements  . . . . . . . . . . . . . . . . . . . . . .  14
   8.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .  14
   9.  Security Considerations . . . . . . . . . . . . . . . . . . .  15
   10. References  . . . . . . . . . . . . . . . . . . . . . . . . .  15
     10.1.  Normative Information References . . . . . . . . . . . .  15
     10.2.  Conceptual ground basis  . . . . . . . . . . . . . . . .  15
     10.3.  Application references . . . . . . . . . . . . . . . . .  15
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  17








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1.  Introduction

   Network coding(NC) is a novel technology that can be seen as the
   generalization of classic point to point coding to coding for network
   flows.  As with classic coding, both information theoretical and
   algebraic codes literature provide the conceptual solid basis of NC.
   Such conceptual basis has clarified NC benefits and corresponding
   tradeoffs, which need to be considered in practical implementations
   of the technology.

   NC does not replace end-to-end (packet-level block) coding, which is
   a well-established technology for the per-flow provision of quality
   of service by trading off delay and reliability.  Instead, NC
   provides coding within and across network flows relying on in-network
   re-encoding based on service-intent-oriented policy strategies.  By
   means of such policy strategies, the provision of quality of service
   that NC can offer can be tailored according to desired network
   service intent.

   For its operation, NC relies on having access to network, computation
   and storage resources throughout the network.  Such novel networking,
   computational and storage ingredients of a coding technology calls
   for novel practical design approaches to truly exploit the potential
   capabilities of NC.

   On the other hand, Network Function Virtualization (NFV) and NC can
   be seen as different ways to address different challenges in the
   design of upcoming network technologies.  Moreover, NC is not a
   traditionally implemented network function in dedicated hardware,
   which are the network functions that have triggered the design of NFV
   architectures.  However, in this document we show the feasibility and
   benefits of virtualizing the network coding function.

   The objective of this document is not to explain network coding
   technology.  The interested reader should find this information
   outside this document.

   The objective of this document is fundamentally two fold.  First, we
   show that NC can be designed as a (modular) network function.  The
   modularity is convenient for the user and is given as sets of
   elementary functionalities (toolboxes) that are defined independent
   of the physical network.  Second, we show that the NC function
   requirements of connectivity, computation and storage resources find
   a natural practical design solution in the integration of the NC
   function with available NFV architectural frameworks.  Such solution
   is described here and it combines network protocol-driven and system
   modular-driven design approaches.




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   The resulting Virtual Network Coding Function (VNCF) can be useful
   for upcoming networking needs derived from network virtualization.

   In order to provide the readers with a flavor of how the ideas
   presented in this draft might be applied to real-world communication
   scenarios, we will describe an interesting use case related to the
   creation of a hybrid satellite-terrestrial infrastructure for the
   effective delivery of multimedia contents to end-users.  The
   architecture in question envisages a combination of multicast,
   simulcast and unicast communication scenarios where satellite links
   are exploited to support local in-network caching.  The satellite
   acts as the interconnection link between distributed in-network
   caches and terrestrial CDN (Cotent Delivery Network) and/or feeds
   edge-network caches at micro-centre locations.

   The example architecture will be orchestrated through an enhanced NFV
   management framework exposing Network Coding functionality as a
   Virtual Network Function (VNF).  Such a function will in our case
   implement a novel "combined coding" technique targeting the
   optimization of multicast-enabled transmissions in the presence of
   caching.  More precisely, it will leverage cutting-edge solutions for
   decentralized random caching which, combined with an original content
   distribution technique based on coded multicast, will allow us to
   abtain "order-optimal" performance.

   In a nutshell, the above mentioned technique allows us to somehow
   multiplex multiple transmission chunks on a single packet, thus
   enabling us to meet the twofold objective of optimizing the use of
   the broadcast communication medium while at the same time
   dramatically increasing the security level of satellite-enabled
   transmissions, by making them resilient to network attacks like
   snooping and eavesdropping.

2.  Conventions used in this document

   The following terms defined in this document can be found in the ETSI
   NFV [etsi_gs_nfv_002_v1.2.1] and the IETF [I-D.irtf-nwcrg-network-
   coding-taxonomy].

   Coherent Network Coding: Source and destination nodes know network
   topology and coding operations at intermediate nodes.

   Noncoherent Network Coding: Source and destination nodes do not know
   network topology and intermediate coding operations.  In this case,
   random network coding can be applied.

   Flow: A stream of physical packets logically grouped from the network
   coding perspective.  These packets may come from the same application



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   (in that case they are identified by the five-tuple: source and
   destination IP address, transport protocol ID, and source and
   destination port of the transport protocol), or come from the same
   source host (in which case they are identified by the 3-tuple source
   and destination IP address, Type of Service (TOS) or Diffserv code
   point(DSCP)).  This distinction depends on the use-case where network
   coding is applied.

   Intra-flow coding: Network coding over payloads belonging to the same
   flow.

   Inter-flow coding: Network coding over payloads belonging to multiple
   flows.

   End-to-end coding : Transport stream is coded and decoded at end-
   points.

   Coding node: Node performing coding operations.

   Virtualized Infrastructure Manager (VIM): functional block that is
   responsible for controlling and managing the NFVI compute, storage
   and network resources, usually within one operator's Infrastructure
   Domain.

   Virtualized Network Function (VNF): implementation of a Network
   Function that can be deployed on a Network Function Virtualization
   Infrastructure (NFVI).

   Virtualized Network Function Manager (VNFM): functional block that is
   responsible for the lifecycle management of VNF.

   NFV Infrastructure (NFVI): totality of all hardware and software
   components which build up the environment in which VNFs are deployed.

   NFV Orchestrator (NFVO): functional block that manages the Network
   Service (NS) lifecycle and coordinates the management of NS
   lifecycle, VNF lifecycle (supported by the VNFM) and NFVI resources
   (supported by the VIM) to ensure an optimized allocation of the
   necessary resources and connectivity.

   NFV Management and Orchestration (NFV-MANO): functions collectively
   provided by NFVO, VNFM, and VIM.

3.  Network coding as a network function







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3.1.  Design domains of the network coding function

   NC design involves different domains.  There are three reasons to
   identify such different domains for the design of network coding
   functions.

   First, network coding is intrinsically multidisciplinary involving at
   least dealing with the design of codes and networking using codes.
   Therefore development of solutions can benefit from a clear
   distinction of in which domain experts are contributing.

   Second, a network coding function is a transversal network function
   that can be used to provide solutions to different types of problems
   such as congestion problems, bottleneck problems, losses problems,
   security problems, etc.  Therefore, there should be more design
   domains other than purely protocol domain as it is the case with
   standard protocols.

   Finally, a network coding function that will operate over softwarised
   networks with cloud storage and computational resources, needs to be
   designed in a way that is close to a functional software
   architecture.

   We identify at least the three domains, as illustrated in the
   following subsections.

3.1.1.  Coding domain

   This is th domain for the design of network coding codebooks,
   coherent or noncoherent encoding/decoding schemes, performance
   benchmarks, appropriate mathematical-to-logic maps, etc.  This is a
   domain fundamentally designed by coding theorists.

   [Editor's note] To be completed...

3.1.2.  Functional domain

   This is the domain for the design of the different sub-functions for
   network coding to achieve the desired design objectives upon
   abstractions of networks and systems.

   This domain jointly requires to consider physical-logical
   abstraction, identification of network coding application to either
   inter-flow or intra-flow network coding, service intent and related
   networking for the provision of quality of service.

   [Editor's note] To be completed...




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3.1.3.  Protocol domain

   This is the domain for the design of headers, initial settings, etc
   for the physical transporting of the network coded information flow
   as one way or interactive protocols.

   [Editor's note] To be completed...

3.2.  Flexible modular design via sets of subfunctions

   In order to provide the designer with sufficient flexibility, NC
   elementary sub-functionalities can be grouped in the functional
   domain as a set of toolboxes that the designer can use.

   We define the three toolboxes described in the following subsections.

3.2.1.  Coding/Re-encoding/Decoding Functionalities (CRDF)

   [Editor's note] To be completed...

3.2.2.  Flow Engineering Functionalities (FEF)

   These subfunctionalities perform optimization of available network
   resources to optimally perform NC to meet the service design targets
   depending on the (statistical) status of the networks (congestion,
   link failures, etc).

   [Editor's note] To be completed...

3.2.3.  Physical/Abstraction Functionalities (PAF)

   These subfunctionalities performing interaction with available
   storage and computation physical resources that are abstracted by the
   other toolboxes.

   [Editor's note] To be completed...

4.  Virtual Network Coding Function

4.1.  Virtualization of flows

   An important differentiating aspect of NC with respect to traditional
   networking technologies is the following.  A network flow for a NC
   network function is understood as a stream of physical packets
   logically grouped from the network coding perspective.

   NC can optimize the NC operation abstracting such physical flow as a
   mathematical model, which can be subject of computational



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   manipulation.  This makes NC to be naturally integrated into a
   virtualized framework of abstract entities such as virtual network or
   network slices.  This is because in the NC case, not only the network
   and resources are abstracted, but also the stream of packets is
   abstracted.

   Consequently, when interpreting NC as a functionality provided to the
   network, NC function virtualization simply consists of integrating
   the NC functional toolboxes described in the previous section into
   existing architectural NFV frameworks.  The virtualization of the
   network flow is managed by the NC function (CRDF toolbox), and the
   virtualization of all the functionalities described in Section 3 has
   no difference with respect to any other network function.

4.2.  Integration with ETSI NFV architecture

   Figure 1 shows our proposed virtual NC network function (VNCF).  It
   is integrated with the ETSI NFV architecture given the abstracted
   underlying physical system/network as part of NFVI.

   The integration naturally includes too exchanges between VNCF and
   NFV-MANO over reference points.

   Clearly, the functionalities of the FEF toolbox need to interact with
   the NFVO, VNFM, and VIM.  Note that the NFVO two main
   responsibilities of orchestration of NFVI resources across VIMs and
   the life-cycle management of network services, fit perfectly the
   needs of the FEF and PAF toolboxes.  Specifically, the FEF can obtain
   available network, connectivity and computation resources, geo-
   statistical status of the networks such as congestion, link failures,
   etc.  With these, NC operation can be optimized to meet the service
   design targets given the service-specific design constraints.  The
   optimization may result into manipulation of the (non-physical) flows
   and other flow engineering policies.  On the other hand, the FEF can
   interact with the VIM to obtain the allocation, upgrade, release, etc
   of NFVI resources.















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        +-------------------------------------------+  +---------------+
        |   Virtualized Network Functions (VNFs)    |  |               |
        |  -------   -------   -------   -------    |  |               |
        |  |     |   |     |   |     |   |     |    |  |               |
        |  | VNF |   | VNF |   |VNCF |   | VNF |    |  |               |
        |  |     |   |     |   |     |   |     |    |  |               |
        |  -------   -------   -------   -------    |  |               |
        +-------------------------------------------+  |               |

        +-------------------------------------------+  |               |
        |         NFV Infrastructure (NFVI)         |  |      NFV      |
        | -----------    -----------    ----------- |  |  Management   |
        | | Virtual |    | Virtual |    | Virtual | |  |      and      |
        | | Compute |    | Storage |    | Network | |  | Orchestration |
        | -----------    -----------    ----------- |  |               |
        | +---------------------------------------+ |  |               |
        | |         Virtualization Layer          | |  |               |
        | +---------------------------------------+ |  |               |
        | +---------------------------------------+ |  |               |
        | | -----------  -----------  ----------- | |  |               |
        | | | Compute |  | Storage |  | Network | | |  |               |
        | | -----------  -----------  ----------- | |  |               |
        | |          Hardware resources           | |  |               |
        | +---------------------------------------+ |  |               |
        +-------------------------------------------+  +---------------+


   Figure 1: ETSI NFV framework with one VNCF box as part of the set of
                              available VNFs

4.3.  Example

   We describe here a high-level example of a general procedure of
   interaction between the VNCF and the NFV-MANO.  The NFV-MANO has
   repositories that hold different information regarding network
   services (NSs) and VNFs (VNCF is part of VNFs).  There are four types
   of repositories as follows:

   o  VNF catalogue represents the repository of all usable VNF
      packages, supporting the creation and management of the VNF
      packages.

   o  NS catalogue represents the repository of all usable NSs.

   o  NFV instances is the repository that holds details of all VNF
      instances and NS instances, represented by either a VNF record or
      a NS record, respectively, during the execution of VNF/NS life-
      cycle management operations.



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   o  NFVI resources is the repository that holds information about NFVI
      resources utilized for the establishment of NS and VNF instances.

   Assume a network abstracted as a set of N coding nodes, each with
   encoding/re-encoding/decoding and (possibly) multi-link connectivity.
   A user of the VNCF wants to provide an ultra-reliable service (e.g.
   mission-critical communications) to the N nodes.  The performance
   objectives are given as a set of N reliability and delay objective
   performance metrics, which are geo-location dependent.  We call this
   VNCF instantiation as a virtual geo-network coding function (VGNCF),
   which is activated and its management and orchestration take place.

   A detailed interaction with the architectural blocks (some under
   definition) is as follows.

   o  TBD

   The next section will briefly introduce a real-world application
   scenario associated woth the effective deivery of multimedia content
   in a hybrid satellite-terrestrial network.

4.3.1.  The SHINE use case

   SHINE stands for "Secure Hybrid In Network caching Environment".  It
   has two main distinctive features, associated with, respectively, the
   broadcast-enabled satellite core and the edge distribution networks.
   Within the former part of the network, we rely on network coding in
   order to define a coded multicast technique allowing us to improve
   both performance and security of communications.  At the edges of the
   distribution network, which also act as in-network caches, we instead
   leverage cutting-edge streaming technologies (namely, MPEG-DASH and/
   or WebRTC) in order to optimize content distribution towards the end
   users of the network.

   A high-level view of the SHINE architecture is reported in Figure 2.
   The picture highlights the main logical components of the
   architecture, in terms of macro-blocks and related functionality.
   Namely, we identify the following elements:

   1.  a source encoder block, taking on the responsibility of properly
       encoding the original content in order to allow for the
       subsequent coded multicast transmission over the satellite
       network;

   2.  the core satellite-enabled communication infrastructure, looking
       after DVB-enabled transmission of coded multicast frames from the
       content provider to the edge caches, both during the cache




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       population phase and during the steady-state operation of the
       CDN;

   3.  two different "flavors"" of edge access networks: (i) a WebRTC-
       enabled access network, included in the architecture in order to
       demonstrate SHINE's operation in the presence of this novel real-
       time communication infrastructure at the edges of the overall
       content delivery architecture; (ii) an MPEG-DASH enabled access
       network, included in the architecture in order to demonstrate
       SHINE's capability of leveraging such a well-assessed web-based
       distribution approach.








































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                                                  +-------+ Satellite GW
                                                /-|       | -
                                            /---  |       |  \-
                                        /---      +-------+    \-
                                     /--             /-  |       \ Network encoder
                                 /---              /-    |        \-     +-------+
                             /---                /-      /          \-   |       |
                          /--                  /-       |             \- |       |
                      /---                   /-         |               \|       |
                  /---                     /-           |                |       |
                --                       /-             |                |       |
           +---+                       /-               /                +-------+
           |   |                     /- Coded Multicast|                  -/
           |   |Edge cache         /-  Transmission    |                -/
           |   |                 /-                    |              -/
           |   |               /-                      /       +----------------+
+---------------+            /-                       |        |                |
|          +---+|          /-                         |        |                |
|               |        /-                           |        |Content Provider|
|               |      /-                             |        |                |
|               |    /-                               /        |                |
|               |   -                                |         |                |
|               | +---+                              |         +----------------+
+---------------+ |   |                            +-|-+              +---+
                  |   | Edge cache                 |   |              |   | Origin
                  |   |                  Edge cache|   |              |   |---+ server
                  |   |                            |   |              |   |   | farm
            +---------------+                      |   |              |   | +-|-+
            |     +---+     |           +---------------+             |   | | | |
            |               |           |          +---+|             +---+ | | |
            |               |           |               |                 | | | |
            |               |           |               |                 +---+ |
            |               |           |               |                   |   |
            |               |           |               |                   +---+
            +---------------+           |               |
        Edge distribution network       +---------------+
                                   Edge distribution network


                       Figure 2: The SHINE use case

   The system components which are of uttermost importance in this
   document, in view of the observation that they can highly benefit
   from the effective utilization of Network Coding as a Virtual Network
   Function are analyzed in further detail in the following.

   The source encoder is a software module implementing the main logic
   behind the proposed coded multicast technique.  It is in charge of



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   transforming the original content and applying the required
   transformations in order to arrive at a representation format that is
   suitable for the subsequent coded multicast transmission.  The
   component in question has indeed to look after both the cache
   population phase and the actual content delivery phase.  The cache
   population phase envisages that the edge caches pre-fetch some
   content, based on appropriate functions of the content library, as
   well as on information about estimated future users' demand for
   content.  During the delivery phase, on the other hand, the source
   forms a multicast "codeword" to be transmitted over the shared link
   in order to meet the actual users' content demands.  As already
   stated, we envisage that the cache population phase is carried out
   through transmission (over the satellite core network connecting
   source node with edge caches) of content chunks.  As to the content
   delivery phase, it takes place through DVB-encapsulated transmission,
   over the satellite network, of coded multicast frames.

   Satellite Core Network is the network segment that basically
   interconnects the Source Encoder, which produces and processes
   multimedia contents, and several Edge Networks, where the in-network
   caches represent the boundary network elements.  The satellite
   network trunk leverages standard DVB-S or DVB-S2 broadcast

   The delivery phase hence occurs after the placement phase, when
   traffic is high and network resources are scarce and expensive (e.g.,
   in the evening).  At the beginning of this phase, each user reveals
   its request for one of the m files.  The server is informed of these
   K requested files.  In response, the server sends RF bits (or the
   equivalent of R files) over the shared link.  The number R is called
   the rate of the server transmission or equivalently load of the
   satellite link.  From the server transmission and its local cache
   content, each user needs to be able to recover their requested files.
   As already anticipated, SHINE looks after both the content placement
   and delivery phases.  The objective is to minimize the rate R with
   which every possible set of user demands can be satisfied.  The
   constraints are the storage limit during content placement and the
   recovery requirement during content delivery.  Both phases are
   generic for both coded and uncoded schemes, but naively performed in
   the uncoded case.  In fact, when relying on uncoded or naive
   multicasting during the delivery phase, it is well known that the
   optimal caching strategy is to cache the top M most popular files at
   each user cache.  Though, this is in general far from optimal when
   coding can be used in the delivery phase.  Thanks to the adoption of
   the dynamically provided Virtual Network Coding Function, SHINE
   discloses the potential of caching-aided code design and illustrates
   its major advantages compared to the optimal caching policy under
   uncoded (naive) multicasting.  In a nutshell, the designed
   architecture shows how the combined use of edge caching and coded



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   multicasting represents a promising approach to simultaneously serve
   multiple unicast demands via coded multicast transmissions, leading
   to order-of-magnitude bandwidth efficiency gains.

5.  Conclusions

   This memo presents a preliminary version of proposal for the design
   of NC as a network function.  It is also discussed that it can be
   virtualized and integrated into a NFV architecture.

6.  Differences with respect to version -01

   Major restructuring of section 3.

7.  Acknowledgements

   The authors want to thank Dr. Harald Skinnemoen for useful comments
   and discussions.  The first author wants to thank Dr. Carlos J.
   Bernardos and Luis M.  Contreras for useful discussions.

   The authors also want to acknowledge the following ongoing projects.

   1.  GEO-VISION - GNSS driven EO and Verifiable Image and Sensor
       Integration for mission-critical Operational Networks.  EU funded
       project under the call H2020-GALILEO-2014-1 by the European
       Global Navigation Satellite Systems Agency (project reference
       641451).

   2.  SatNetCode - Satellite Network-Coding for high performance,
       semantic-aware mission-critical visual communications.  This
       project is funded by the European Space Agency, under contract
       No. 4000115046/15/NL/US.

   3.  HENCSAT - Highly Efficient Network Coding for Satellite
       Applications Test-bed.  This project is funded by the European
       Space Agency, under contract No.  4000118143/16/NL/EM.

   4.  SHINE - Secure Hybrid In Network caching Environment.  This
       project is funded by the European Space Agency, under Contract
       No. 4000118273/16/NL/CLP.

8.  IANA Considerations

   This memo includes no request to IANA.







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9.  Security Considerations

   This memo includes no Network Coding Function Virtualization -
   specific security definitions yet.

10.  References

10.1.  Normative Information References

   [etsi_gs_nfv_002_v1.2.1]
              "Network Function Virtualisation (NFV); Architectural
              Framework", 2014.

   [etsi_nvf_whitepaper]
              "Network Functions Virtualisation (NFV). White Paper 2",
              2014.

   [I-D.irtf-nwcrg-network-coding-taxonomy]
              Firoiu, V., Adamson, B., Roca, V., Adjih, C., Bilbao, J.,
              Fitzek, F., Masucci, A., and M. Montpetit, "Network Coding
              Taxonomy", draft-irtf-nwcrg-network-coding-taxonomy-01
              (work in progress), October 2016.

   [RFC6363]  Watson, M., Begen, A., and V. Roca, "Forward Error
              Correction (FEC) Framework", RFC 6363, 2011.

10.2.  Conceptual ground basis

   [AHL00]    Ahlswede, R., Cai, N., Y. R. Li, S., and R. W. Yeung,
              "Network information flow", in IEEE Trans. Inform. Theory,
              vol. 46, pp. 1204-1216, July 2000.

   [KOE03]    Koetter, R. and M. Medard, "An algebraic approach to
              network coding", in IEEE/ACM Trans. on Networking, vol.
              11, n. 5., pp. 782-795, October 2003.

   [LI03]     Y.R.Li, S., W. Yeung, R., and N. Cai, "Linear network
              coding", in IEEE Trans. Inform. Theory, vol. 49, n. 2.,
              pp. 371-381, February 2003.

10.3.  Application references

   [ALE13]    Alegre-Godoy, R. and M. A. Vazquez-Castro, "Spatial
              Diversity with Network Coding for ON/OFF Satellite
              Channels", in IEEE Communications Letters, vol. 17, No. 8,
              pp. 1612-1615, August 2013.





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   [ALE15]    Alegre-Godoy, R. and M. A. Vazquez-Castro, "Network Coded
              Multicast over Multi-beam Satellite Systems", in
              Mathematical Problems in Engineering, vol. 2015, Article
              ID 364234, May 2015.

   [DO16.1]   Do-Duy, T. and M. A. Vazquez-Castro, "Design of
              Virtualized Network Coding Functionality foR Reliability
              Control of Communication Services over Satellite",
              submitted to Special Issue on Network Coding.
              International Journal of Satellite Communications and
              Networking, 2016.

   [Do16.2]   Do-Duy, T. and M. A. Vazquez-Castro, "Network coding
              function virtualization", in IEEE 17th International
              Workshop on Signal Processing Advances in Wireless
              Communications (SPAWC), September 2016, INVIED PAPER.

   [HAN15]    Hansen, J., E. Lucani, D., Krigslund, J., Medard, M., and
              F. H. P. Fitzek, "Network coded software defined
              networking: enabling 5G transmission and storage
              networks", in IEEE Communications Magazine, 2015.

   [HEI09]    Heide, J., V. Pedersen, M., H. P. Fitzek, F., and T.
              Larsen, "Network Coding for Mobile Devices - Systematic
              Binary Random Rateless Codes", in ICC Workshops, 2009.

   [SAX15]    Saxena, P. and M. A. Vazquez-Castro, "DARE: DoF-Aided
              Random Encoding for Network Coding over Lossy Line
              Networks", in IEEE Communications Letters, vol. 19, No. 8,
              pp. 1374-1377, August 2015.

   [SZA15]    Szabo, D., Nemeth, F., Sonkoly, B., Gulyas, A., and F. H.
              P. Fitzek, "Towards the 5G revolution: A software defined
              network architecture exploiting network coding as a
              service", in SIGCOMM Comput. Commun, 2015.

   [VAZ15.1]  A. Vazquez-Castro, M., "A Geometric Approach to Dynamic
              Network Coding", in Information Theory Workshop, Jeju,
              Korea, October 2015.

   [VAZ15.2]  A. Vazquez-Castro, M., "Subspace coding over Fq-linear
              erasure satellite channels", in 12th International
              Symposium on Wireless Communication Systems, pp. 216-220,
              August 2015.







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   [VAZ15.3]  A. Vazquez-Castro, M. and P. Saxena, "Network Coding over
              Satellite: From Theory to Design and Performance", in
              Volume 154 of the series Lecture Notes of the Institute
              for Computer Sciences, Social Informatics and
              Telecommunications Engineering, pp. 315-327, September
              2015, INVITED PAPER.

Authors' Addresses

   M.A. Vazquez-Castro
   Autonomus University of Barcelona
   Campus de Bellaterra
   Barcelona, 08391
   Spain

   Email: angeles.vazquez@uab.es


   Tan Do-Duy
   Autonomus University of Barcelona
   Campus de Bellaterra
   Barcelona, 08391
   Spain

   Email: tan.doduy@uab.es


   Simon Pietro Romano
   University of Napoli Federico II
   Via Claudio 21
   Napoli, 80125
   Italy

   Email: spromano@unina.it


   Antonia Maria Tulino
   University of Napoli Federico II
   Via Claudio 21
   Napoli, 80125
   Italy

   Email: antoniamaria.tulino@unina.it








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