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SFC WG                                                     CJ. Bernardos
Internet-Draft                                                      UC3M
Intended status: Experimental                                  A. Mourad
Expires: September 10, 2020                                 InterDigital
                                                           March 9, 2020


            NSH extensions for local distributed SFC control
             draft-bernardos-sfc-nsh-distributed-control-00

Abstract

   Service function chaining (SFC) allows the instantiation of an
   ordered set of service functions and subsequent "steering" of traffic
   through them.  In order to set up and maintain SFC instances, a
   control plane is required, which typically is centralized.  In
   certain environments, such as fog computing ones, such centralized
   control might not be feasible, calling for distributed SFC control
   solutions.  This document specifies several NSH extensions to provide
   in-band SFC control signaling.

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
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   This Internet-Draft will expire on September 10, 2020.

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   Copyright (c) 2020 IETF Trust and the persons identified as the
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   carefully, as they describe your rights and restrictions with respect



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   to this document.  Code Components extracted from this document must
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Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
   2.  Terminology . . . . . . . . . . . . . . . . . . . . . . . . .   4
   3.  Local SFC control signaling extending NSH . . . . . . . . . .   5
   4.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   7
   5.  Security Considerations . . . . . . . . . . . . . . . . . . .   8
   6.  Acknowledgments . . . . . . . . . . . . . . . . . . . . . . .   8
   7.  References  . . . . . . . . . . . . . . . . . . . . . . . . .   8
     7.1.  Normative References  . . . . . . . . . . . . . . . . . .   8
     7.2.  Informative References  . . . . . . . . . . . . . . . . .   8
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .   8

1.  Introduction

   Virtualization of functions provides operators with tools to deploy
   new services much faster, as compared to the traditional use of
   monolithic and tightly integrated dedicated machinery.  As a natural
   next step, mobile network operators need to re-think how to evolve
   their existing network infrastructures and how to deploy new ones to
   address the challenges posed by the increasing customers' demands, as
   well as by the huge competition among operators.  All these changes
   are triggering the need for a modification in the way operators and
   infrastructure providers operate their networks, as they need to
   significantly reduce the costs incurred in deploying a new service
   and operating it.  Some of the mechanisms that are being considered
   and already adopted by operators include: sharing of network
   infrastructure to reduce costs, virtualization of core servers
   running in data centers as a way of supporting their load-aware
   elastic dimensioning, and dynamic energy policies to reduce the
   monthly electricity bill.  However, this has proved to be tough to
   put in practice, and not enough.  Indeed, it is not easy to deploy
   new mechanisms in a running operational network due to the high
   dependency on proprietary (and sometime obscure) protocols and
   interfaces, which are complex to manage and often require configuring
   multiple devices in a decentralized way.

   Service Functions are widely deployed and essential in many networks.
   These Service Functions provide a range of features such as security,
   WAN acceleration, and server load balancing.  Service Functions may
   be instantiated at different points in the network infrastructure
   such as data center, the WAN, the RAN, and even on mobile nodes.




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   Service functions (SFs), also referred to as VNFs, or just functions,
   are hosted on compute, storage and networking resources.  The hosting
   environment of a function is called Service Function Provider or
   NFVI-PoP (using ETSI NFV terminology).

   Services are typically formed as a composition of SFs (VNFs), with
   each SF providing a specific function of the whole service.  Services
   also referred to as Network Services (NS), according to ETSI
   terminology.

   With the arrival of virtualization, the deployment model for service
   function is evolving to one where the traffic is steered through the
   functions wherever they are deployed (functions do not need to be
   deployed in the traffic path anymore).  For a given service, the
   abstracted view of the required service functions and the order in
   which they are to be applied is called a Service Function Chain
   (SFC).  An SFC is instantiated through selection of specific service
   function instances on specific network nodes to form a service graph:
   this is called a Service Function Path (SFP).  The service functions
   may be applied at any layer within the network protocol stack
   (network layer, transport layer, application layer, etc.).

   The concept of fog computing has emerged driven by the Internet of
   Things (IoT) due to the need of handling the data generated from the
   end-user devices.  The term fog is referred to any networked
   computational resource in the continuum between things and cloud.  A
   fog node may therefore be an infrastructure network node such as an
   eNodeB or gNodeB, an edge server, a customer premises equipment
   (CPE), or even a user equipment (UE) terminal node such as a laptop,
   a smartphone, or a computing unit on-board a vehicle, robot or drone.

   In fog computing, the functions composing an SFC are hosted on
   resources that are inherently heterogeneous, volatile and mobile
   [I-D.bernardos-sfc-fog-ran].  This means that resources might appear
   and disappear, and the connectivity characteristics between these
   resources may also change dynamically.  These scenarios call for
   distributed SFC control solutions, where there are SFC pseudo
   controllers, enabling autonomous SFC self-orchestration capabilities.
   The concept of SFC pseudo controller (P-CTRL) is described in
   [I-D.bernardos-sfc-distributed-control], as well different procedures
   for their discovery and initialization.

   This document specifies several NSH extensions to provide in-band SFC
   control signaling.







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2.  Terminology

   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].

   The following terms used in this document are defined by the IETF in
   [RFC7665]:

      Service Function (SF): a function that is responsible for specific
      treatment of received packets (e.g., firewall, load balancer).

      Service Function Chain (SFC): for a given service, the abstracted
      view of the required service functions and the order in which they
      are to be applied.  This is somehow equivalent to the Network
      Function Forwarding Graph (NF-FG) at ETSI.

      Service Function Forwarder (SFF): A service function forwarder is
      responsible for forwarding traffic to one or more connected
      service functions according to information carried in the SFC
      encapsulation, as well as handling traffic coming back from the
      SF.

      SFI: SF instance.

      Service Function Path (SFP): the selection of specific service
      function instances on specific network nodes to form a service
      graph through which an SFC is instantiated.

   The following terms are used in this document:

      SFC Pseudo Controller (P-CTRL): logical entity
      [I-D.bernardos-sfc-distributed-control], complementing the SFC
      controller/orchestrator found in current architectures and
      deployments.  It is service specific, meaning that it is defined
      and meaningful in the context of a given network service.
      Compared to existing SFC controllers/orchestrators, which manage
      multiple SFCs instantiated over a common infrastructure, pseudo
      controllers are constrained to service specific lifecycle
      management.

      SFC Central Controller (C-CTRL): central control plane logical
      entity in charge of configuring and managing the SFC components
      [RFC7665].







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3.  Local SFC control signaling extending NSH

                                o
                         node B |
                       +--------|-+    F1+-.-.-+F2+-.-.-+F3 SFC
                       | ........ |
                       | |P-CTRL| |
                       | ........ |
                     +-.-.-+F2    |
            o       /  +---+------+                 ________
            |      .       .                      _(        )_
   +--------|-+   /       /                     _( +--------+ )_
   |          |  .       .                     (_  | C-CTRL |  _)
   |          | /       /                        (_+--------+_)
   |          |.       |                           (________)
   |     +-.-./        .
   |    F1    |        |         ( (oo) )
   +----------+        .  o         /\  ........
      node A           |  |        /\/\ |P-CTRL|
                 +-----.--|-+     /\/\/\........
                 |     |    |    /\/  \/\  F3
                 |     .    |      node D
                 |     |    |
                 |     +    |
                 |          |
                 +----------+
                    node C

                      Figure 1: Example SFC scenario

   Figure 1 shows an exemplary scenario to show the use of the new NSH
   extensions.  In this scenario, there is no mobility, so nodes are not
   moving out of radio coverage.  In this scenario, at a given point in
   time the service demands increase, which requires F2 (running at node
   B) and F3 (running at node D) to have more resources allocated, as
   otherwise the service would not meet the required SLA.  This is
   detected by the P-CTRL through service-specific local OAM monitoring.
   Once detected the need of scaling up the resources at nodes B and D,
   P-CTRL notifies this through in-band signaling in the actual data
   packets processed by the SFC.  This is shown in Figure 2.  Note that
   the use of in-band signaling provides a more efficient way of
   conveying the signaling, as well as supports multiple NS lifecycle
   management operations (even addressing different nodes) to be
   conveyed in a single message.







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                 +--------+    +--------+    +--------+
                 |  F1@A  |    |  F2@B  |    |  F3@D  |
                 +--------+    +--------+    +--------+

                 +--------+    +--------+    +--------+
                 |Transp. |    |Transp. |    |Transp. |
                 | header |    | header |    | header |
                 +--------+    +--------+    +--------+
                 |  NSH   |    |  NSH   |    |  NSH   |
                 | header |    | header |    | header |
                 |  F3@D  |    |  F3@D  |    |  F3@D  |
                 |scale up|    |scale up|    |scale up|
                 |  F2@B  |    |  F2@B  |    |        |
                 |scale up|    |scale up|    |        |
   +--------+    +--------+    +--------+    +--------+    +--------+
   | Packet |    | Packet |    | Packet |    | Packet |    | Packet |
   +--------+    +--------+    +--------+    +--------+    +--------+
      ===>          ===>          ===>          ===>          ===>

     Figure 2: In-band NS lifecycle management signaling extending NSH

   The NS lifecycle management commands conveyed in the NSH are
   transported as a new NSH metadata (MD) type (e.g., Type 3, as current
   NSH specifications only support 2 types), as shown next:

    0                   1                   2                   3
    0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |Ver|O|U|    TTL    |   Length  |U|U|U|U|MD Type| Next Protocol |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |          Service Path Identifier              | Service Index |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                                                               |
   ~       Variable-Length NS lifecycle management commands        ~
   |                                                               |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   The format of the new variable-length field for NS lifecycle
   management commands is shown next:

    0                   1                   2                   3
    0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |        NS lifecycle cmd       |      Type     |U|    Length   |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                   Variable-Length Metadata                    |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+




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   o  NS lifecycle cmd: the NS lifecycle management command.  This is a
      non-limiting list of the commands:

      *  Scale in.

      *  Scale out.

      *  Scale up.

      *  Scale down.

      *  Instantiate function.

      *  Terminate function.

      *  Configure function.

      *  Upgrade function.

      *  Update function.

      *  Update function.

      *  Onboard VNFD.

      *  Onboard OAMD.

      *  Sync state.

      *  Request to overcome CTRL.

      *  CTRL activation.

   o  Type: indicates the explicit type of command carried out.  This
      depends on the orchestration framework implementation.

   o  Unassigned bit: one unassigned bit is available for future use.
      This bit MUST NOT be set, and it MUST be ignored on receipt.

   o  Unassigned bit: one unassigned bit is available for future use.
      This bit MUST NOT be set, and it MUST be ignored on receipt.

4.  IANA Considerations

   N/A.






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5.  Security Considerations

   TBD.

6.  Acknowledgments

   The work in this draft has been partially supported by the H2020
   5Growth (Grant 856709) and 5G-DIVE projects (Grant 859881).

7.  References

7.1.  Normative References

   [I-D.bernardos-sfc-distributed-control]
              Bernardos, C. and A. Mourad, "Distributed SFC control for
              fog environments", draft-bernardos-sfc-distributed-
              control-01 (work in progress), January 2020.

   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119,
              DOI 10.17487/RFC2119, March 1997,
              <https://www.rfc-editor.org/info/rfc2119>.

7.2.  Informative References

   [I-D.bernardos-sfc-fog-ran]
              Bernardos, C., Rahman, A., and A. Mourad, "Service
              Function Chaining Use Cases in Fog RAN", draft-bernardos-
              sfc-fog-ran-06 (work in progress), September 2019.

   [RFC7665]  Halpern, J., Ed. and C. Pignataro, Ed., "Service Function
              Chaining (SFC) Architecture", RFC 7665,
              DOI 10.17487/RFC7665, October 2015,
              <https://www.rfc-editor.org/info/rfc7665>.

Authors' Addresses

   Carlos J. Bernardos
   Universidad Carlos III de Madrid
   Av. Universidad, 30
   Leganes, Madrid  28911
   Spain

   Phone: +34 91624 6236
   Email: cjbc@it.uc3m.es
   URI:   http://www.it.uc3m.es/cjbc/





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   Alain Mourad
   InterDigital Europe

   Email: Alain.Mourad@InterDigital.com
   URI:   http://www.InterDigital.com/














































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