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Versions: 00 01 02                                                      
service function chain                                             C. Wu
Internet-Draft                                       Zhejiang University
Intended status: Standards Track                                 W. Meng
Expires: June 6, 2015                                            C. Wang
                                                         ZTE Corporation
                                                        December 3, 2014


            Redundancy Mechanism for Service Function Chains
                   draft-meng-sfc-chain-redundancy-01

Abstract

   This document discusses about hot standby analysis of service
   function instances (SFIs) under different scenarios.  The document
   provides requirement and use cases and also describes the suitable
   scenarios that each solution may be deployed in.

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
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   Internet-Drafts are draft documents valid for a maximum of six months
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   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 June 6, 2015.

Copyright Notice

   Copyright (c) 2014 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
   publication of this document.  Please review these documents
   carefully, as they describe your rights and restrictions with respect
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   include Simplified BSD License text as described in Section 4.e of
   the Trust Legal Provisions and are provided without warranty as



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   described in the Simplified BSD License.


Table of Contents

   1.  Introduction . . . . . . . . . . . . . . . . . . . . . . . . .  3
   2.  Convention and Terminology . . . . . . . . . . . . . . . . . .  4
   3.  Redundancy Mechanisms  . . . . . . . . . . . . . . . . . . . .  5
     3.1.  Homogeneous Backup . . . . . . . . . . . . . . . . . . . .  5
     3.2.  Heterogeneous Backup . . . . . . . . . . . . . . . . . . .  5
     3.3.  Internal Backup  . . . . . . . . . . . . . . . . . . . . .  6
     3.4.  External Backup  . . . . . . . . . . . . . . . . . . . . .  6
   4.  Redirect Service Function Paths  . . . . . . . . . . . . . . .  8
   5.  Control Plane Considerations . . . . . . . . . . . . . . . . .  9
   6.  Data Plane Considerations  . . . . . . . . . . . . . . . . . . 10
   7.  Load Balancing Considerations  . . . . . . . . . . . . . . . . 11
   8.  Normative References . . . . . . . . . . . . . . . . . . . . . 12
   Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 13

































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1.  Introduction

   The object of Service Function Chains (SFC) is trying to unload
   services from nodes in traditional network and deal with such
   services through service function chains.  As a result of this,
   redundancy of service function instances needs to be standardize,
   rather than maintain as an internal mechanism in a traditional
   network device.

   Many SFs might be located in large-scale networks, such as ISP
   networks or enterprise ones, where exist a large number of customers.
   In each service function, these customers which is served by a single
   service function instance (SFI) may experience service degradation in
   case of the presence of the single point of exceptional failure.
   Therefore, redundancy of the SFI will be strongly desired in order to
   deliver highly available services.

   This memo describes some use cases of redundancy among SFIs under
   typical scenarios.
































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2.  Convention and 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 terms about SFC are defined in [I-D.ietf-sfc-problem-statement]
   and [I-D.ietf-sfc-architecture].











































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3.  Redundancy Mechanisms

   As illustrated in Figure 1, two SFIs (SFI1 and SFI1') are deployed
   for redundancy purposes.  This is the reference architecture for the
   mechanisms we describe in this memo.

             ,---.
            /     \
   --------(  SFI1 |-
            \     /  \
             `-^-'    \     ,---.
               |       \-- /     \------->  Master Service Function Path
    Backup --> |          (  SFI2 )
             ,-v-.    .... \     /.......>  Backup Service Function Path
            /     \  .      `---'
   ........( SFI1' ).
            \     /
             `---'


                         Figure 1: Reference Model

3.1.  Homogeneous Backup

   Figure 2 illustrates a homogeneous backup cases.  In this scenario,
   each of those master SFIs will have a corresponding backup SFI.

               ,---.       ,---.       ,---.
              /     \     /     \     /     \
             (  SFI1 |   (  SFI2 |   (  SFI3 |
              \     /     \     /     \     /
               `-^-'       `-^-'       `-^-'
                 |           |           |
                 |           |           |
                 |           |           |
               ,-v-.       ,-v-.       ,-v-.
              /     \     /     \     /     \
             ( SFI1' )   ( SFI2' )   ( SFI3' )
              \     /     \     /     \     /
               `---'       `---'       `---'

                    Figure 2: Homogeneous Backup Model

3.2.  Heterogeneous Backup

   Figure 3 illustrates a heterogeneous backup cases.  In this scenario,
   each of those master SFIs might have more than one corresponding
   backup SFIs.



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                ,---.             ,---.
               /     \           /     \
              (  SFI1 |         (  SFI2 |
               \     /         / \     / \
                `-^-'         /   `---'   \
                  |           |            |
                  |           |            |
                  |           |            |
                ,-v-.       ,-v-.        ,-v-.
               /     \     /     \      /     \
              ( SFI1' )   ( SFI2' )    ( SFI2'')
               \     /     \     /      \     /
                `---'       `---'        `---'

                   Figure 3: Heterogeneous Backup Model

3.3.  Internal Backup

   Figure 4 illustrates a internal backup cases.  In this scenario, both
   sides of backup are located in a same Service Function Node.

       +----------------------------------------+
       |     ,---.       ,---.        ,---.     |
       |    /     \     /     \      /     \    |
       |   (  SFI1 <---> SFI1' |    (  SFI2 |   | <-- Service Function Node
       |    \     /     \     /      \     /    |
       |     `---'       `---'        `---'     |
       +----------------------------------------+

                      Figure 4: Internal Backup Model

3.4.  External Backup

   Figure 5 illustrates a external backup cases.  In this scenario, each
   side of backup is located in its own Service Function Node.
















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       +---------------------------------------+
       |     ,---.       ,---.       ,---.     |
       |    /     \     /     \     /     \    |
       |   (  SFI1 |   ( SFI2  |   (  SFI3 |   | <-- Service Function Node 1
       |    \     /     \     /     \     /    |
       |     `-^-'       `-^-'       `-^-'     |
       +-------|-----------|-----------|-------+
               |           |           |   <------- Network
       +-------|-----------|-----------|-------+
       |     ,-v-.       ,-v-.       ,-v-.     |
       |    /     \     /     \     /     \    |
       |   ( SFI1' |   ( SFI2' |   ( SFI3' |   | <-- Service Function Node 2
       |    \     /     \     /     \     /    |
       |     `---'       `---'       `---'     |
       +---------------------------------------+

                      Figure 5: External Backup Model


































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4.  Redirect Service Function Paths

   As described in [ietf-sfc-architecture], a Service Function Path is
   the instantiation of the defined SFC.

   In case of planned maintenance operations or exceptional failure of
   Service Function Node, The SFP MUST be changed to prevent disrupting
   the normal traffic.











































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5.  Control Plane Considerations

   TBD
















































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6.  Data Plane Considerations

   TBD
















































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7.  Load Balancing Considerations

   TBD
















































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8.  Normative References

   [I-D.ietf-sfc-architecture]
              Halpern, J. and C. Pignataro, "Service Function Chaining
              (SFC) Architecture", draft-ietf-sfc-architecture-02 (work
              in progress), September 2014.

   [I-D.ietf-sfc-problem-statement]
              Quinn, P. and T. Nadeau, "Service Function Chaining
              Problem Statement", draft-ietf-sfc-problem-statement-10
              (work in progress), August 2014.

   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119, March 1997.

   [RFC2865]  Rigney, C., Willens, S., Rubens, A., and W. Simpson,
              "Remote Authentication Dial In User Service (RADIUS)",
              RFC 2865, June 2000.

































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Authors' Addresses

   Wu Chunming
   Zhejiang University
   No.38 Zheda Road, Xihu District
   Hangzhou
   China

   Email: wuchunming@zju.edu.cn


   Wei Meng
   ZTE Corporation
   No.50 Software Avenue, Yuhuatai District
   Nanjing
   China

   Email: meng.wei2@zte.com.cn,vally.meng@gmail.com


   Cui Wang
   ZTE Corporation
   No.50 Software Avenue, Yuhuatai District
   Nanjing
   China

   Email: wang.cui1@zte.com.cn
























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