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NFVRG                                                           R. Szabo
Internet-Draft                                                A. Csaszar
Intended status: Informational                                  Ericsson
Expires: September 10, 2015                               K. Pentikousis
                                                                    EICT
                                                                 M. Kind
                                                     Deutsche Telekom AG
                                                                D. Daino
                                                          Telecom Italia
                                                                Z. Qiang
                                                                Ericsson
                                                              H. Woesner
                                                                   BISDN
                                                           March 9, 2015


 Unifying Carrier and Cloud Networks: Problem Statement and Challenges
                    draft-unify-nfvrg-challenges-01

Abstract

   The introduction of network and service functionality virtualization
   in carrier-grade networks promises improved operations in terms of
   flexibility, efficiency, and manageability.  In current practice,
   virtualization is controlled through orchestrator entities that
   expose programmable interfaces according to the underlying resource
   types.  Typically this means the adoption of, on the one hand,
   established data center compute/storage and, on the other, network
   control APIs which were originally developed in isolation.  Arguably,
   the possibility for innovation highly depends on the capabilities and
   openness of the aforementioned interfaces.  This document introduces
   in simple terms the problems arising when one follows this approach
   and motivates the need for a high level of programmability beyond
   policy and service descriptions.  This document also summarizes the
   challenges related to orchestration programming in this unified cloud
   and carrier network production environment.

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 http://datatracker.ietf.org/drafts/current/.





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   Internet-Drafts are draft documents valid for a maximum of six months
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   Copyright (c) 2015 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

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   described in the Simplified BSD License.

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
   2.  Terms and Definitions . . . . . . . . . . . . . . . . . . . .   3
   3.  Motivations . . . . . . . . . . . . . . . . . . . . . . . . .   4
   4.  Problem Statement . . . . . . . . . . . . . . . . . . . . . .  10
   5.  Challenges  . . . . . . . . . . . . . . . . . . . . . . . . .  10
   5.1.  Orchestration . . . . . . . . . . . . . . . . . . . . . . .  10
   5.2.  Resource description  . . . . . . . . . . . . . . . . . . .  10
   5.3.  Dependencies (de-composition) . . . . . . . . . . . . . . .  11
   5.4.  Elastic VNF . . . . . . . . . . . . . . . . . . . . . . . .  11
   5.5.  Measurement and analytics . . . . . . . . . . . . . . . . .  12
   6.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .  13
   7.  Security Considerations . . . . . . . . . . . . . . . . . . .  13
   8.  Acknowledgement . . . . . . . . . . . . . . . . . . . . . . .  13
   9.  Informative References  . . . . . . . . . . . . . . . . . . .  13
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  15

1.  Introduction

   To a large degree there is agreement in the network research,
   practitioner, and standardization communities that rigid network
   control limits the flexibility and manageability of speedy service
   creation, as discussed in [NSC] and the references therein.  For
   instance, it is not unusual that today an average service creation
   time cycle exceeds 90 hours, whereas given the recent advances in



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   virtualization and cloudification one would be interested in service
   creation times in the order of minutes [EU-5GPPP-Contract] if not
   seconds.

   Flexible service definition and creation start by formalizing the
   service into the concept of network function forwarding graphs, such
   as the ETSI VNF Forwarding Graph [ETSI-NFV-Arch] or the ongoing work
   in IETF [I-D.ietf-sfc-problem-statement].  These graphs represent the
   way in which service end-points (e.g., customer access) are
   interconnected with a set of selected network functionalities such as
   firewalls, load balancers, and so on, to deliver a network service.
   Service graph representations form the input for the management and
   orchestration to instantiate and configure the requested service.
   For example, ETSI defined a Management and Orchestration (MANO)
   framework in [ETSI-NFV-MANO].  We note that throughout such a
   management and orchestration framework different abstractions may
   appear for separation of concerns, roles or functionality, or for
   information hiding.

   Compute virtualization is central to the concept of Network Function
   Virtualization (NFV).  However, carrier-grade services demand that
   all components of the data path, such as Network Functions (NFs),
   virtual NFs (VNFs) and virtual links, meet key performance
   requirements.  In this context, the inclusion of Data Center (DC)
   platforms, such as OpenStack [OpenStack], into the SDN infrastructure
   is far from trivial.

   In this document we examine the problems arising as one combines
   these two formerly isolated environments in an effort to create a
   unified production environment and discuss the associated emerging
   challenges.  Our goal is the definition of a production environment
   that allows multi-vendor and multi-domain operation based on open and
   interoperable implementations of the key entities described in the
   remainder of this document.

2.  Terms and Definitions

   We use the term compute and "compute and storage" interchangeably
   throughout the document.  Moreover, we use the following definitions,
   as established in [ETSI-NFV-Arch]:

   NFV:  Network Function Virtualization - The principle of separating
      network functions from the hardware they run on by using virtual
      hardware abstraction.

   NFVI PoP:  NFV Infrastructure Point of Presence - Any combination of
      virtualized compute, storage and network resources.




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   NFVI:  NFV Infrastructure - Collection of NFVI PoPs under one
      orchestrator.

   VNF:  Virtualized Network Function - a software-based network
      function.

   VNF FG:  Virtualized Network Function Forwarding Graph - an ordered
      list of VNFs creating a service chain.

   MANO:  Management and Orchestration - In the ETSI NFV framework
      [ETSI-NFV-MANO], this is the global entity responsible for
      management and orchestration of NFV lifecycle.

   Further, we make use of the following terms:

   NF:  a network function, either software-based (VNF) or appliance-
      based.

   SW:  a (routing/switching) network element with a programmable
      control plane interface.

   DC:  a data center network element which in addition to a
      programmable control plane interface offers a DC control interface

   LSI:  Logical Switch Instance - a software switch instance.

3.  Motivations

   Figure 1 illustrates a simple service graph comprising three network
   functions (NFs).  For the sake of simplicity, we will assume only two
   types of infrastructure resources, namely SWs and DCs as per the
   terminology introduced above, and ignore appliance-based NFs for the
   time being.  The goal is to implement the given service based on the
   available infrastructure resources.


                              fr2  +---+ fr3
                              +->o-|NF2|-o-+
                              |  4 +---+ 5 |
                        +---+ |            V +---+
                  1-->o-|NF1|-o----------->o-|NF3|-o-->8
                      2 +---+ 3     fr1    6 +---+ 7


                          Figure 1: Service graph

   The service graph definition contains NF types (NF1, NF2, NF3) along
   with the



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   o  corresponding ports (NF1:{2,3}; NF2:{4,5}; NF3:{6,7})

   o  service access points {1,8} corresponding to infrastructure
      resources,

   o  definition of forwarding behavior (fr1, fr2, fr3)

   The forwarding behavior contains classifications for matching of
   traffic flows and corresponding outbound forwarding actions.

   Assume now that we would like to use the infrastructure (topology,
   network and software resources) depicted in Figure 2 and Figure 3 to
   implement the aforementioned service graph.  That is, we have three
   SWs and two Points of Presence (PoPs) with DC software resources at
   our disposal.


                                   +---+
                                +--|SW3|--+
                                |  +---+  |
                    +---+       |         |      +---+
                 1  |PoP|    +---+      +---+    |PoP|  8
                 o--|DC1|----|SW2|------|SW4 |---|DC2|--o
                    +---+    +---+      +---+    +---+

                [---SP1---][--------SP2-------][---SP3----]

                    Figure 2: Infrastructure resources


                       +----------+
                       |  +----+  |PoP DC (== NFVI PoP)
                       |  | CN |  |
                       |  +----+  |
                       |   |  |   |
                       |  +----+  |
                     o-+--| SW |--+-o
                       |  +----+  |
                       +----------+


       Figure 3: A virtualized Point of Presence (PoP) with software
                       resources (Compute Node - CN)

   In the simplest case, all resources would be part of the same service
   provider (SP) domain.  We need to ensure that each entity in Figure 2
   can be procured from a different vendor and therefore
   interoperability is key for multi-vendor NFVI deployment.  Without



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   such interoperability different technologies for data center and
   network operation result in distinct technology domains within a
   single carrier.  Multi-technology barriers start to emerge hindering
   the full programmability of the NFVI and limiting the potential for
   rapid service deployment.

   We are also interested in a multi-operation environment, where the
   roles and responsibilities are distributed according to some
   organizational structure within the organization.  Finally, we are
   interested in multi-provider environment, where different
   infrastructure resources are available from different service
   providers (SPs).  Figure 2 indicates a multi-provider environment in
   the lower part of the figure as an example.  We expect that this type
   of deployments will become more common in the future as they are well
   suited with the elasticity and flexibility requirements [NSC].

   Figure 2 also shows the service access points corresponding to the
   overarching domain view, i.e., {1,8}. In order to deploy the service
   graph of Figure 1 on the infrastructure resources of Figure 2, we
   will need an appropriate mapping which can be implemented in
   practice.  In Figure 4 we illustrate a resource orchestrator (RO) as
   a functional entity whose task is to map the service graph to the
   infrastructure resources under some service constraints and taking
   into account the NF resource descriptions.



























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                         fr2  +---+  fr3
                         +->o-|NF2|-o-+
                         |  4 +---+ 5 |
                   +---+ |            V +---+
             1-->o-|NF1|-o----------->o-|NF3|-o-->8
                 2 +---+ 3     fr1    6 +---+ 7

                                  ||
                                  ||
              +--------+          \/        SP0
              |   NF   |   +---------------------+
              |Resource|==>|Resource Orchestrator|==> MAPPING
              | Descr. |   |      (RO)           |
              +--------+   +---------------------+
                                  /\
                                  ||
                                  ||

                                +---+
                             +--|SW3|--+
                             |  +---+  |
                 +---+       |         |      +---+
              1  |PoP|     +---+     +---+    |PoP|  8
              o--|DC1|-----|SW2|-----|SW4|----|DC2|--o
                 +---+     +---+     +---+    +---+

             [---SP1---][--------SP2-------][---SP3----]
             [-------------------SP0-------------------]

   Figure 4: Resource Orchestrator: information base, inputs and output

   NF resource descriptions are assumed to contain information necessary
   to map NF types to a choice of instantiable VNF flavor or a selection
   of an already deployed NF appliance and networking demands for
   different operational policies.  For example, if energy efficiency is
   to be considered during the decision process then information related
   to energy consumption of different NF flavors under different
   conditions (e.g., network load) should be included in the resource
   description.

   Note that we also introduce a new service provider (SP0) which
   effectively operates on top of the virtualized infrastructure offered
   by SP1, SP2 and SP3.

   In order for the RO to execute the resource mapping (which in general
   is a hard problem) it needs to operate on the combined control plane
   illustrated in Figure 5.  In this figure we mark clearly that the
   interfaces to the compute (DC) control plane and the SDN (SW) control



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   plane are distinct and implemented through different interfaces/APIs.
   For example, Ic1 could be the Apache CloudStack API, while Ic2 could
   be a control plane protocol such as ForCES or OpenFlow
   [I-D.irtf-sdnrg-layer-terminology].  In this case, the orchestrator
   at SP0 (top part of the figure) needs to maintain a tight
   coordination across this range of interfaces.

                               +---------+
                               |Orchestr.|
                               |   SP0   |
                          _____+---------+_____
                         /          |          \
                        /           V Ic2       \
                       |       +---------+       |
                   Ic1 V       |SDN Ctrl |       V  Ic3
              +---------+      |   SP2   |      +---------+
              |Comp Ctrl|      +---------+      |Comp Ctrl|
              |  SP1    |        /  |  \        |   SP3   |
              +---------+    +---   V   ----+   +---------+
                   |         |    +----+    |         |
                   |         |    |SW3 |    |         |
                   V         |    +----+    |         V
                  +----+     V   /      \   V     +----+
               1  |PoP |    +----+      +----+    |PoP |  8
               o--|DC1 |----|SW2 |------|SW4 |----|DC2 |--o
                  +----+    +----+      +----+    +----+

              [----SP1---][---------SP2--------][---SP3----]
              [---------------------SP0--------------------]

    Figure 5: The RO Control Plane view.  Control plane interfaces are
    inticated with (line) arrows.  Data plane connections are indicated
                            with simple lines.

   In the real-world, however, orchestration operations do not stop, for
   example, at the DC1 level as depicted in Figure 5.  If we (so-to-
   speak) "zoom into" DC1 we will see a similar pattern and the need to
   coordinate SW and DC resources within DC1 as illustrated in Figure 6.
   As depicted, this edge PoP includes compute nodes (CNs) and SWs which
   in most of the cases will also contain an internal topology.

   In Figure 6, IcA is an interface similar to Ic2 in Figure 5, while
   IcB could be, for example, OpenStack Nova or similar.  The Northbound
   Interface (NBI) to the Compute Controller can use Ic1 or Ic3 as shown
   in Figure 5.






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                             NBI
                              |
                         +---------+
                         |Comp Ctrl|
                         +---------+
                       +----+     |
                   IcA V          | IcB:to CNs
                +---------+       V
                |SDN Ctrl |    |          |  ext port
                +---------+  +---+      +---+
                  to|SW      |SW |      |SW |
                    +->     ,+--++.._  _+-+-+
                    V    ,-"   _|,,`.""-..+
                       _,,,--"" |    `.   |""-.._
                  +---+      +--++     `+-+-+    ""+---+
                  |SW |      |SW |      |SW |      |SW |
                  +---+    ,'+---+    ,'+---+    ,'+---+
                  |   | ,-"  |   | ,-"  |   | ,-"  |   |
                +--+ +--+  +--+ +--+  +--+ +--+  +--+ +--+
                |CN| |CN|  |CN| |CN|  |CN| |CN|  |CN| |CN|
                +--+ +--+  +--+ +--+  +--+ +--+  +--+ +--+


             Figure 6: PoP DC Network with Compute Nodes (CN)

   In turn, each single Compute Node (CN) may also have internal
   switching resources (see Figure 7).  In a carrier environment, in
   order to meet data path requirements, allocation of compute node
   internal distributed resources (blades, CPU cores, etc.) may become
   equivalently important.

                             +-+  +-+ +-+  +-+
                             |V|  |V| |V|  |V|
                             |N|  |N| |N|  |N|
                             |F|  |F| |F|  |F|
                             +-+  +-+ +-+  +-+
                             |   /   /       |
                             +---+ +---+ +---+
                             |LSI| |LSI| |LSI|
                             +---+ +---+ +---+
                               |  /        |
                             +---+       +---+
                             |NIC|       |NIC|
                             +---+       +---+
                               |           |


          Figure 7: Compute Node with internal switching resource



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4.  Problem Statement

   The motivational examples of Section 3 illustrate that compute
   virtualization implicitly involves network virtualization.  On the
   other hand, if one starts with an SDN network and adds compute
   resources to network elements, then compute resources must be
   assigned to some virtualized network resources if offered to clients.
   That is, we observe that compute virtualization is implicitly
   associated with network virtualization.  Furthermore, virtualization
   leads to recursions with clients (redefining and) reselling resources
   and services [I-D.huang-sfc-use-case-recursive-service].

   We argue that given the multi-level virtualization of compute,
   storage and network domains, automation of the corresponding resource
   provisioning needs a recursive programmatic interface.  The current
   separated compute and network programming interfaces cannot provide
   such recursions and cannot satisfy key requirements for multi-vendor,
   multi-technology and multi-provider interoperability environments.
   Therefore we foresee the necessity of a recursive programmatic
   interface for joint compute, storage and network provisioning.

5.  Challenges

   We summarize in this section the key questions and challenges, which
   we hope will initiate further discussions in the NFVRG community.

5.1.  Orchestration

   Firstly, as motivated in Section 3, orchestrating networking
   resources appears to have a recursive nature at different levels of
   the hierarchy.  Would a programmatic interface at the combined
   compute and network abstraction better support this recursive and
   constraint-based resource allocation?

   Secondly, can such a joint compute, storage and network programmatic
   interface allow an automated resource orchestration similar to a
   recursive SDN architecture [ONF-SDN-ARCH]?

5.2.  Resource description

   Prerequisite for joint placement decisions of compute, storage and
   network is the adequate description of available resources.  This
   means that the interfaces (IcA, IcB etc. in Figure 5 and Figure 6)
   are of bidirectional nature, exposing resources as well as reserving.
   There have been manifold attempts to create frameworks for resource
   description, most prominently RDF of W3C, NDL, the GENI RPC and its
   concept of Aggregate Managers, ONF's TTP and many more.




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   Quite naturally, all attempts to standardize "arbitrary" resource
   descriptions lead to creating ontologies, complex graphs describing
   relations of terms to each other.

   Practical descriptions of compute resources are currently focusing on
   number of logical CPU cores, available RAM and storage, allowing,
   e.g., the OpenStack Nova scheduler to meet placement decisions.  In
   heterogeneous network and compute environments, hardware may have
   different acceleration capabilities (e.g., AES-NI or hardware random
   number generators), so the notion of logical compute cores is not
   expressive enough.  In addition, the network interfaces (and link
   load) provide important information on how fast a certain VNF can be
   executed in one node.

   This may lead to a description of resources as VNF-FGs themselves.
   Networking resource (SW) may expose the capability to forward and
   process frames in, e.g., OpenFlow TableFeatures reply.  Compute nodes
   in the VNF-FG would expose lists of capabilities like the presence of
   AES hardware acceleration, Intel DPDK support, or complex functions
   like a running web server.  An essential part of the compute node's
   capability would be the ability to run a certain VNF of type X within
   a certain QoS spec.  As the QoS is service specific, it can only be
   exposed by a control function within the instantiated VNF-FG.

5.3.  Dependencies (de-composition)

   Salt [SALT], Puppet [PUPPET], Chef [CHEF] and Ansible [ANSIBLE] are
   tools to manage large scale installations of virtual machines in DC
   environments.  Essentially, the decomposition of a complex function
   into its dependencies is encoded in "recipes" (Chef).

   OASIS TOSCA [TOSCA] specification aims at describing application
   layer services to automate interoperable deployment in alternative
   cloud environments.  The TOSCA specification "provides a language to
   describe service components and their relationships using a service
   topology".

   Is there a dependency (decomposition) abstraction suitable to drive
   resource orchestration between application layer descriptions (like
   TOSCA) and cloud specific installations (like Chef recipes)?

5.4.  Elastic VNF

   In many use cases, a VNF may not be designed for scaling up/down, as
   scaling up/down may require a restart of the VNF which the state data
   may be lost.  Normally a VNF may be capable for scaling in/out only.
   Such VNF is designed running on top of a small VM and grouped as a
   pool of one VNF function.  VNF scaling may crossing multiple NFVI



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   PoPs (or data center)s in order to avoid limitation of the NVFI
   capability.  At cross DC scaling, the result is that the new VNF
   instance may be placed at a remote cloud location.  At VNF scaling,
   it is a must requirement to provide the same level of Service Level
   Agreement (SLA) including performance, reliability and security.

   In general, a VNF is part of a VNF Forwarding Graph (VNF FG), meaning
   the data traffic may traverse multiple stateful and stateless VNF
   functions in sequence.  When some VNF instances of a given service
   function chain are placed / scaled out in a distant cloud execution,
   the service traffic may have to traverse multiple VNF instances which
   are located in multiple physical locations.  In the worst case, the
   data traffic may ping-pong between multiple physical locations.
   Therefore it is important to take the whole service function chain's
   performance into consideration when placing and scaling one of its
   VNF instance.  Network and cloud resources need mutual
   considerations, see [I-D.zu-nfvrg-elasticity-vnf].

5.5.  Measurement and analytics

   Programmable, dynamic, and elastic VNF deployment requires that the
   Resource Orchestrator (RO) entities obtain timely information about
   the actual operational conditions between different locations where
   VNFs can be placed.  Scaling VNFs in/out/up/down, VNF execution
   migration and VNF mobility, as well as right-sizing the VNFI resource
   allocations is a research area that is expected to grow in the coming
   years as mechanisms, heuristics, and measurement and analytics
   frameworks are developed.

   For example, Veitch et al.  [IAF] point out that NFV deployment will
   "present network operators with significant implementation
   challenges".  They look into the problems arising from the lack of
   proper tools for testing and diagnostics and explore the use of
   embedded instrumentation.  They find that in certain scenarios fine-
   tuning resource allocation based on instrumentation can lead to at
   least 50% reduction in compute provisioning.  In this context, three
   categories emerge where more research is needed.

   First, in the compute domain, performance analysis will need to
   evolve significantly from the current "safety factor" mentality which
   has served well carriers in the dedicated, hardware-based appliances
   era.  In the emerging softwarized deployments, VNFI will require new
   tools for planning, testing, and reliability assurance.

   Second, in the network domain, performance measurement and analysis
   will play a key role in determining the scope and range of VNF
   distribution across the resources available.  For example, IETF has
   worked on the standardization of IP performance metrics for years.



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   The Two-Way Active Measurement Protocol (TWAMP) could be employed,
   for instance, to capture the actual operational state of the network
   prior to making RO decisions.  TWAMP management, however, still lacks
   a standardized and programmable management and configuration data
   model.  We expect that as VNFI programmability gathers interest from
   network carriers several IETF protocols will be revisited in order to
   bring them up to date with respect to the current operational
   requirements.  To this end, NFVRG can play an active role in
   identifying future IETF standardization directions.

   Third, non-technical considerations which relate to business aspects
   or priorities need to be modeled and codified so that ROs can take
   intelligent decisions.  Energy efficiency and cost, for example, can
   steer NFV placement.  In NFVI deployments operational practices such
   as follow-the-sun will be considered as earlier research in the data
   center context implies.

6.  IANA Considerations

   This memo includes no request to IANA.

7.  Security Considerations

   TBD

8.  Acknowledgement

   The authors would like to thank the UNIFY team for inspiring
   discussions and in particular Fritz-Joachim Westphal for his comments
   and suggestions on how to refine this draft.

   This work is supported by FP7 UNIFY, a research project partially
   funded by the European Community under the Seventh Framework Program
   (grant agreement no. 619609).  The views expressed here are those of
   the authors only.  The European Commission is not liable for any use
   that may be made of the information in this document.

9.  Informative References

   [ANSIBLE]  Ansible Inc., "Ansible Documentation", 2015,
              <http://docs.ansible.com/index.html>.

   [CHEF]     Chef Software Inc., "An Overview of Chef", 2015,
              <https://docs.chef.io/chef_overview.html>.







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   [ETSI-NFV-Arch]
              ETSI, "Architectural Framework v1.1.1", Oct 2013,
              <http://www.etsi.org/deliver/etsi_gs/
              NFV/001_099/002/01.01.01_60/gs_NFV002v010101p.pdf>.

   [ETSI-NFV-MANO]
              ETSI, "Network Function Virtualization (NFV) Management
              and Orchestration V0.6.1 (draft)", Jul. 2014,
              <http://docbox.etsi.org/ISG/NFV/Open/Latest_Drafts/
              NFV-MAN001v061-%20management%20and%20orchestration.pdf>.

   [EU-5GPPP-Contract]
              5G-PPP Association, "Contractual Arrangement: Setting up a
              Public- Private Partnership in the Area of Advance 5G
              Network Infrastructure for the Future Internet between the
              European Union and the 5G Infrastructure Association", Dec
              2013, <http://5g-ppp.eu/contract/>.

   [I-D.huang-sfc-use-case-recursive-service]
              Huang, C., Zhu, J., and P. He, "SFC Use Cases on Recursive
              Services", draft-huang-sfc-use-case-recursive-service-01
              (work in progress), January 2015.

   [I-D.ietf-sfc-problem-statement]
              Quinn, P. and T. Nadeau, "Service Function Chaining
              Problem Statement", draft-ietf-sfc-problem-statement-13
              (work in progress), February 2015.

   [I-D.irtf-sdnrg-layer-terminology]
              Haleplidis, E., Pentikousis, K., Denazis, S., Salim, J.,
              Meyer, D., and O. Koufopavlou, "SDN Layers and
              Architecture Terminology", draft-irtf-sdnrg-layer-
              terminology-04 (work in progress), October 2014.

   [I-D.zu-nfvrg-elasticity-vnf]
              Qiang, Z. and R. Szabo, "Elasticity VNF", draft-zu-nfvrg-
              elasticity-vnf-01 (work in progress), March 2015.

   [IAF]      Veitch, P., McGrath, M. J., and Bayon, V., "An
              Instrumentation and Analytics Framework for Optimal and
              Robust NFV Deployment", Communications Magazine, vol. 53,
              no. 2 IEEE, February 2015.

   [NSC]      John, W., Pentikousis, K., et al., "Research directions in
              network service chaining", Proc. SDN for Future Networks
              and Services (SDN4FNS), Trento, Italy IEEE, November 2013.





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   [ONF-SDN-ARCH]
              ONF, "SDN architecture", Jun. 2014,
              <https://www.opennetworking.org/images/stories/downloads/
              sdn-resources/technical-reports/
              TR_SDN_ARCH_1.0_06062014.pdf>.

   [OpenStack]
              The OpenStack project, "Openstack cloud software", 2014,
              <http://openstack.org>.

   [PUPPET]   Puppet Labs., "Puppet 3.7 Reference Manual", 2015,
              <http://docs.puppetlabs.com/puppet/3.7/reference/>.

   [SALT]     SaltStack, "Salt (Documentation)", 2015,
              <http://docs.saltstack.com/en/latest/contents.html>.

   [TOSCA]    OASIS Standard, "Topology and Orchestration Specification
              for Cloud Applications Version 1.0", November 2013,
              <http://docs.oasis-open.org/tosca/TOSCA/v1.0/os/
              TOSCA-v1.0-os.html>.

Authors' Addresses

   Robert Szabo
   Ericsson Research, Hungary
   Irinyi Jozsef u. 4-20
   Budapest  1117
   Hungary

   Email: robert.szabo@ericsson.com
   URI:   http://www.ericsson.com/


   Andras Csaszar
   Ericsson Research, Hungary
   Irinyi Jozsef u. 4-20
   Budapest  1117
   Hungary

   Email: andras.csaszar@ericsson.com
   URI:   http://www.ericsson.com/










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   Kostas Pentikousis
   EICT GmbH
   EUREF-Campus Haus 13
   Torgauer Strasse 12-15
   10829 Berlin
   Germany

   Email: k.pentikousis@eict.de


   Mario Kind
   Deutsche Telekom AG
   Winterfeldtstr. 21
   10781 Berlin
   Germany

   Email: mario.kind@telekom.de


   Diego Daino
   Telecom Italia
   Via Guglielmo Reiss Romoli 274
   10148 Turin
   Italy

   Email: diego.daino@telecomitalia.ite


   Zu Qiang
   Ericsson
   8400, boul. Decarie
   Ville Mont-Royal, QC  8400
   Canada

   Email: zu.qiang@ericsson.com
   URI:   http://www.ericsson.com/


   Hagen Woesner
   BISDN
   Koernerstr. 7-10
   Berlin  10785
   Germany

   Email: hagen.woesner@bisdn.de
   URI:   http://www.bisdn.de





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