High-level VNF Descriptors using NEMO
draft-aranda-nfvrg-recursive-vnf-00

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NFVRG                                                P. Aranda Gutierrez
Internet-Draft                                                DRL. Lopez
Intended status: Informational                                Telefonica
Expires: December 23, 2016                                 June 21, 2016

                 High-level VNF Descriptors using NEMO
                  draft-aranda-nfvrg-recursive-vnf-00

Abstract

   Current efforts in the scope of Network Function Virtualisation(NFV)
   propose YAML-based descriptors for Virtual Network Functions (VNFs).
   These descriptors are human-readable but hardly understandable by
   humans.  On the other hand, there has been an effort proposed to the
   IETF to define a human-readable (and understandable) representation
   for networks, known as NEMO.  In this draft, we propose a simple
   extension to NEMO to accomodate VNFDs in a similar manner as inline
   assembly is integrated in higher-level programming languages.

   This approach enables the creation of recursive VNF forwarding graphs
   in Service Descriptors, practically making them recursive.

Status of This Memo

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   This Internet-Draft will expire on December 23, 2016.

Copyright Notice

   Copyright (c) 2016 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
   (http://trustee.ietf.org/license-info) in effect on the date of

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   publication of this document.  Please review these documents
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   described in the Simplified BSD License.

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
   2.  Terminology and abbreviations . . . . . . . . . . . . . . . .   3
   3.  Prior art . . . . . . . . . . . . . . . . . . . . . . . . . .   3
     3.1.  Virtual network function descriptors  . . . . . . . . . .   3
     3.2.  NEMO  . . . . . . . . . . . . . . . . . . . . . . . . . .   4
   4.  Additional requirements on NEMO . . . . . . . . . . . . . . .   5
     4.1.  Referencing VNFDs in a NodeModel  . . . . . . . . . . . .   5
     4.2.  Referencing the network interfaces of a VNF in a
           NodeModel . . . . . . . . . . . . . . . . . . . . . . . .   5
     4.3.  An example  . . . . . . . . . . . . . . . . . . . . . . .   6
   5.  Conclusion  . . . . . . . . . . . . . . . . . . . . . . . . .   7
   6.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   7
   7.  Security Considerations . . . . . . . . . . . . . . . . . . .   7
   8.  Acknowledgement . . . . . . . . . . . . . . . . . . . . . . .   7
   9.  References  . . . . . . . . . . . . . . . . . . . . . . . . .   8
     9.1.  Normative References  . . . . . . . . . . . . . . . . . .   8
     9.2.  Informative References  . . . . . . . . . . . . . . . . .   8
     9.3.  URIs  . . . . . . . . . . . . . . . . . . . . . . . . . .   8
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .   8

1.  Introduction

   Currently, there is a lot of activity going on to use NFV in the
   network.  From the point of view of the orchestration, Virtual
   Network Functions are blocks that are deployed in the infrastructure
   as independent units.  They provide for one layer of components (VNF
   components(VNFCs)) below, i.e. a set of VNFCs accessible to a VNF
   provider can be composed into VNFs.  However, there is no simple way
   to use existing VNFs as components in VNFs with a higher degree of
   complexity.  In addition, VNFDs used in different open source MANO
   frameworks are YAML-based files, which despite being human readable,
   are not easy to understand.

   On the other hand, there has been recently an attempt to work on a
   modelling language for networks (NEMO).  This language is human-
   readable and provides a NodeModel construct to describe nodes that
   supports recursiveness.  In this draft, we propose an addition to
   NEMO to make it interact with VNFDs supported by a NFV MANO
   framework.  This integration creates a new language for VNFDs that is

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   recursive, allowing VNFs to be created based on the definitions of
   existing VNFs.

   This draft uses OpenMANO and OSM descriptor references as an example
   for the lowest level descriptors that are imported into NEMO.
   Conceptually, other descriptor formats like TOSCA can also be used at
   this level.

2.  Terminology and abbreviations

   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 [RFC2119].

3.  Prior art

3.1.  Virtual network function descriptors

   Virtual network function descriptors (VNFDs) are used in the
   Management and orchestration (MANO) framework of the ETSI NFV to
   achieve the optimal deployment of virtual network functions (VNFs).
   The Virtual Infrastructure Manager (VIM) uses this information to
   place the functions optimally.  VNFDs include information of the
   components of a specific VNF and their interconnection to implement
   the VNF, in the form of a forwarding graph.  In addition to the
   forwarding graph, the vnfd includes information regarding the
   interfaces of the VNF.  These are then used to connect the VNF to
   either physical or logical interfaces once it is deployed.

   There are different MANO frameworks available.  For this draft, we
   will concentrate on the example of OpenMANO [1], which usesYAML [2].
   Taking the example from the (public) OpenMANO github repository, we
   can easily identify the virtual interfaces of the sample VNFs in
   their descriptors:

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          +----------------------------+
          |                            |
    mgt0  |     +---------------+      |   ge0
          |     |               |      |
       ---+-----+  Template VM  +------+------
          |     |               |      |
          |     +---+--------+--+      |
          |         |        |         |
          +---------+--------+---------+
                    |        |
                  xe0       xe1

   vnf:
       name: TEMPLATE
       description: This is a template to help in the creation of
       # class: parent      # Optional. Used to organize VNFs
       external-connections:
       -   name:              mgmt0
           type:              mgmt
           VNFC:              TEMPLATE-VM
           local_iface_name:  mgmt0
           description:       Management interface
       -   name:              xe0
           type:              data
           VNFC:              TEMPLATE-VM
           local_iface_name:  xe0
           description:       Data interface 1
       -   name:              xe1
           type:              data
           VNFC:              TEMPLATE-VM
           local_iface_name:  xe1
           description:       Data interface 2
       -   name:              ge0
           type:              bridge
           VNFC:              TEMPLATE-VM
           local_iface_name:  ge0
           description:       Bridge interface

       Figure 1: Sample VNF and descriptor (source: OpenMANO github)

3.2.  NEMO

   The Network Modeling (NEMO) language is described in
   [I-D.xia-sdnrg-nemo-language].  It provides a simple way of
   describing network scenarios.  The language is based on a two-stage
   process.  In the first stage, models for nodes, links and other
   entities are defined.  In the second stage, the defined models are
   instanciated.  The NEMO language also allows for behavioural

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   descriptions.  A variant of the NEMO language is used in the
   OpenDaylight NEMO northbound API [3].

   NEMO allows to define NodeModels, which are then instanciated in the
   infrastructure.  NodeModels are recursive and can be build with basic
   node types or with previously defined NodeModels.  An example for a
   script defining a NodeModel is shown below:

   CREATE NodeModel dmz
     Property string: location-fw, string: location-n2,
       string: ipprefix, string: gatewayip, string: srcip,
       string: subnodes-n2;
     Node fw1
       Type fw
       Property location: location-fw,
         operating-mode: layer3;
   ...

                  Figure 2: Creating a NodeModel in NEMO

4.  Additional requirements on NEMO

   In order to integrate VNFDs into NEMO, we need to take into account
   two specifics of VNFDs, which cannot be expressed in the current
   language model.  Firstly, we need a way to reference the file which
   holds the VNFD provided by the VNF developer.  This will normally be
   a universal resource identifier (URI).  Additionally, we need to make
   the NEMO model aware of the virtual network interfaces.

4.1.  Referencing VNFDs in a NodeModel

   As explained in the introduction, in order integrate VNFDs into the
   NEMO language in the easiest way we need to reference the VNFD as a
   Universal Resource Identifier (URI) as defined in RFC 3986 [RFC3986].
   To this avail, we define a new element in the NodeModel to import the
   VNFD:

   CREATE NodeModel NAME <node_model_name>
     IMPORT VNFD FROM <vnfd_uri>

4.2.  Referencing the network interfaces of a VNF in a NodeModel

   As shown in Figure 1, VNFDs include an exhaustive list of interfaces,
   including the interfaces to the management network.  However, since
   these interfaces may not be significant for specific network
   scenarios and since interface names in the VNFD may not be adequate

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   in NEMO, we propose to define a new element in the node model, namely
   the ConnectionPoint.

   CREATE NodeModel NAME <node_model_name>
     DEFINE ConnectionPoint <cp_name> FROM VNFD:<iface_from_vnfd>

4.3.  An example

   Once these two elements are included in the NEMO language, it is
   possibly to recursively define NodeModel elements that use VNFDs in
   the lowest level of recursion.  Firstly, we create NodeModels from
   VNFDs:

   CREATE NodeModel NAME SampleVNF
       IMPORT VNFD from https://github.com/nfvlabs/openmano.git
   /openmano/vnfs/examples/dataplaneVNF1.yaml
       DEFINE ConnectionPoint data_inside as VNFD:ge0
       DEFINE ConnectionPoint data_outside as VNFD:ge1

          Import from a sample VNFD from the OpenMANO repository

   Then we can reuse these NodeModels recursively to create complex
   NodeModels:

   CREATE NodeModel NAME ComplexNode
       Node InputVNF TYPE SampleVNF
       Node OutputVNF TYPE ShaperVNF
       DEFINE ConnectionPoint input
       DEFINE ConnectionPoint output
       CONNECTION input_connection FROM input TO InputVNF:data_inside
           TYPE p2p
       CONNECTION output_connection FROM output TO ShaperVNF:wan
           TYPE p2p
       CONNECTION internal FROM InputVNF:data_outside TO ShaperVNF:lan
           TYPE p2p

                        Create a composed NodeModel

   This NodeModel definition creates a composed model linking the
   SampleVNF created from the VNFD with a hypothetical ShaperVNF defined
   elsewhere.  This definition can be represented graphically as
   follows:

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       +------------------------------------------------------+
       |       ComplexVNF                                     |
       |      +-------------+           +-------------+       |
    input     |             |           |             |     output
       +------+  SampleVNF  +-----------+  ShaperVNF  +-------+
       |      |             |           |             |       |
       |      +-------------+           +-------------+       |
       |  data_inside   data_outside   lan           wan      |
       +------------------------------------------------------+

                                 Figure 3

   In ETSI NFV, a network service is described by one or more VNFs that
   are connected through one or more network VNFFGs.  This is no more
   than what is defined in the composed NodeModel shown if Figure 3.  By
   using NEMO, we provide a simple way to define VNF forwarding
   graphs(VNF-FGs) in network service descriptors in a recursive way.

5.  Conclusion

   With the strategy defined in this document, we are able to link a
   low-level VNF description into a high-level description language for
   networks like NEMO.  Effectively, we are introducing recursiveness in
   VNFDs, allowing complex service descriptors to be built by reusing
   previously tested descriptors graphs as building blocks.

   Although we have used the OpenMANO descriptor format in this
   document, other descriptors and concepts (i.e. as those used by TOSCA
   [4]) can also be used as the lowest level in this extension to the
   NEMO language.

6.  IANA Considerations

   This draft includes no request to IANA.

7.  Security Considerations

   The IMPORT construct allows referencing external resources.
   Developers using it in NEMO scripts are advised to verify the source
   of those external resources, and whenever possible, rely on sources
   with a verifiable identity through cryptographic methods.

8.  Acknowledgement

   This work has been partially performed in the scope of the
   SUPERFLUIDITY project, which has received funding from the European

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   Union's Horizon 2020 research and innovation programme under grant
   agreement No.671566 (Research and Innovation Action).

9.  References

9.1.  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,
              <http://www.rfc-editor.org/info/rfc2119>.

   [RFC3986]  Berners-Lee, T., Fielding, R., and L. Masinter, "Uniform
              Resource Identifier (URI): Generic Syntax", STD 66,
              RFC 3986, DOI 10.17487/RFC3986, January 2005,
              <http://www.rfc-editor.org/info/rfc3986>.

9.2.  Informative References

   [I-D.xia-sdnrg-nemo-language]
              Xia, Y., Jiang, S., Zhou, T., Hares, S., and Y. Zhang,
              "NEMO (NEtwork MOdeling) Language", draft-xia-sdnrg-nemo-
              language-04 (work in progress), April 2016.

9.3.  URIs

   [1] https://github.com/nfvlabs/openmano

   [2] yaml.org

   [3] https://wiki.opendaylight.org/view/NEMO:Main

   [4] http://docs.oasis-open.org/tosca/tosca-nfv/v1.0/tosca-nfv-
       v1.0.html

Authors' Addresses

   Pedro A. Aranda Gutierrez
   Telefonica I+D
   Zurbaran, 10
   Madrid  28010
   Spain

   Email: pedroa.aranda@telefonica.com

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   Diego R. Lopez
   Telefonica I+D
   Zurbaran, 12
   Madrid  28010
   Spain

   Email: diego.r.lopez@telefonica.com

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