[Search] [txt|pdf|bibtex] [Tracker] [Email] [Diff1] [Diff2] [Nits]

Versions: 00 01                                                         
<Service Function Chaining>                              Truong-Xuan Do
Internet Draft                                             Younghan Kim
Intended status: Informational               Soongsil University, Korea
Expires:   April 2016                                      Oct 20, 2015




      High Availability mechanism for Service Function Chains
              draft-xuan-sfc-chain-high-availability-01


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), its areas, and its working groups.  Note that
   other groups may also distribute working documents as Internet-
   Drafts.

   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."

   The list of current Internet-Drafts can be accessed at
   http://www.ietf.org/1id-abstracts.html

   The list of Internet-Draft Shadow Directories can be accessed at
   http://www.ietf.org/shadow.html

   This Internet-Draft will expire on April 2016.

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 to this document.



<Do, et al.>               Expires April 20,2016               [Page 1]


Internet-Draft       <High Availability in SFC>            Oct 20, 2015




Abstract

   This document describes mechanisms to achieve the high
   availability of the service function chains. This document
   considers the high availability in the perspective of entire chain.
   This means the SFC control plane needs to take into account some
   metrics related service chain in addition to individual service
   functions. This document covers both stateless and stateful service
   functions as well.


Table of Contents


   1. Introduction...................................................3
   2. Conventions used in this document..............................3
   3. High availability architecture of SFC..........................4
      3.1. Metrics for back-up SFPs..................................5
      3.2 SFP with all stateless service functions...................6
      3.3 SFP with stateful service funtions.........................7
   4. Security Considerations........................................8
   5. IANA Considerations............................................8
   6. References.....................................................8
      6.1. Normative References......................................8
      6.2. Informative References....................................8





<Do, et al.>               Expires April 20,2016               [Page 2]


Internet-Draft       <High Availability in SFC>           Oct 20, 2015


1. Introduction

   Service function chaining currently is redesigned with the support
   of the software-defined network (SDN) and network function
   virtualization (NFV) which provide more flexible and dynamical
   end-to-end services.

   In order to ensure the high availability of service function
   chains, some traditional mechanisms for individual service function
   are reused (e.g. Active/Standby or Active/Active). These mechanisms
   are based on the deployment of the backup or redundant service
   functions. The recovery of whole service chain relies on the
   recovery of individual service function.

   This document describe a mechanism which ensure the high
   availability of service chain based on some metrics of whole chain.
   The mechanism also considers both stateless and stateful service
   functions in the chain.


2. Conventions used in this document

   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 RFC-2119 [RFC2119].


        The terms about SFC are defined in [RFC7498] and
        [I-D.ietf-sfc-architecture]

<Do, et al.>               Expires April 20,2016               [Page 3]


Internet-Draft       <High Availability in SFC>           Oct 20, 2015


3. High availability architecture of SFC

        Figure 1. shows the architecture for achieving the high
        availability of the SFC. We make assumptions that each service
    function has several instances which are connected to different
        service function forwarders (SFF). Each service function path (SFP)
        is created by the combination of different service instances of
        different service functions. We propose a new entity called SFC
    HA manager which is responsible for monitoring metrics which belong
        not only to the individual service functions, such as fail-over,
        load condition, but also the whole service chain, such as, latency,
        total load, and traffic engineering. The SFC HA Manager takes
        responsibilities of making the backup SFPs. SFC HA manager should
        be located in the control plane part [I-D.ietf-sfc-control-plane]
        of SFC architecture


                         [SFC HA Manager]

            +****************+********+***>> back-up SFP
            +|.......+........|........|.........+.....>> current SFP
            ||       |        |        |         |
           SFI1     SFI2     SFI2     SFI3     SFI3
            |        |        |        |         |
            +---+----+        +----+---+         |
                |                  |             |
             SFFI1               SFFI2        SFFI3

                                Figure 1. High availability architecture of SFC



<Do, et al.>               Expires April 20,2016               [Page 4]


Internet-Draft       <High Availability in SFC>            Oct 20, 2015

3.1. Metrics for back-up SFPs

        Some metrics for whole service function chain are listed below:

        Fail-over: a back-up SFP with the replacement of failed service
        functions

        Total latency: a back-up SFP with better latency

        Total bandwidth: a back-up SFP with highest bandwidth

        Total path: a back-up SFP with shortest path

        Total load: a back-up SFP with the lowest load

        Traffic engineering: a back-up SFP with the pre-defined traffic
        engineering goals



<Do, et al.>               Expires April 20,2016               [Page 5]


Internet-Draft       <High Availability in SFC>            Oct 20, 2015

3.2 SFP with all stateless service functions

        Procedures for making a back-up service function path

        + Gather and monitor the states of current service function paths
        + Evaluate the current SFPs based on collected data and above
          metrics
        + HA manager makes back-up SFPs for current SFP
        + When a critical event occurs, the back-up SFP can be invoked and
          replace the current SFP.
    + The information about new SFP (back-up) is updated to all
          corresponding SFFs.



<Do, et al.>               Expires April 20,2016               [Page 6]


Internet-Draft       <High Availability in SFC>            Oct 20, 2015



3.3 SFP with stateful service funtions

    Procedures for making a back-up service function path

        + Gather and monitor the states of current service function paths
        + Evaluate the current SFPs based on collected data and above
          metrics
        + HA manager makes back-up SFPs for current SFP
                - For stateful service functions in the SFP, internal state
                  management for each service function is required and
                  synchronized with the same kind of service function when
                  creating a back-up SFP
                - State synchronization can be handled by the direct
                  communication between two same kind service functions

        + When a critical event occurs, the back-up SFP can be invoked and
          replace the current SFP.
    + The information about new SFP (back-up) is updated to all
          corresponding SFFs.



<Do, et al.>               Expires April 20,2016               [Page 7]


Internet-Draft       <High Availability in SFC>            Oct 20, 2015



4. Security Considerations

TBD.

5. IANA Considerations

TBD.

6. References

6.1. Normative References


   [RFC7498]
              Quinn, P. and T. Nadeau, "Problem Statement for Service
                          Function Chaining", RFC 7498, April 2015.



6.2. Informative References

        [I-D.ietf-sfc-architecture]

              Halpern, J. and C. Pignataro, "Service Function Chaining
              (SFC) Architecture", draft-ietf-sfc-architecture-11 (work
              in progress), July 2015.

        [I-D.ietf-sfc-control-plane]
                           H. Li, Q. Wu, O. Huang, etc. al., "Service Function
                           Chaining (SFC) Control Plane Components & Requirements",
                           draft-ietf-sfc-control-plane-00, Aug 2015





<Do, et al.>               Expires April 20,2016               [Page 8]


Internet-Draft       <High Availability in SFC>            Oct 20, 2015


Authors' Addresses

   Truong-Xuan Do
   Soongsil University
   4F Hyungnam Engineering Bldg. 424,
   (156-743) 511 Sangdo-Dong, Dongjak-Gu, Seoul, Korea

   Phone: +82 10 4473 6869
   Email: xuan@dcn.ssu.ac.kr


   Younghan Kim
   Soongsil University
   4F Hyungnam Engineering Bldg. 424,
   (156-743) 511 Sangdo-Dong, Dongjak-Gu, Seoul, Korea

   Phone: +82-2-820-0904
   Email: younghak@ssu.ac.kr































<Do, et al.>               Expires April 20,2016               [Page 9]