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Versions: 00 01                                                         
SFC WG                                                          Ting. Ao
Internet-Draft                                                    Bo. Wu
Intended status: Standards Track                         ZTE Corporation
Expires: November 30, 2015                                  May 29, 2015


                Hierarchical SFC for DC Interconnection
                draft-ao-sfc-for-dc-interconnect-00.txt

Abstract

   Sometimes some SFs of a SFC are provided by several DC networks.
   That means a SFC may cross several SFs in different DC network.  How
   to establish such SFC that is across several DCs is what we want to
   state.  In this document, a hierarchical SFC method is proposed.  It
   will cover data plane, control plane for such hierarchical SFC.  And
   it includes requirements of the SFC Gateway for every DC network that
   provide SF for SFC.

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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   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 November 30, 2015.

Copyright Notice

   Copyright (c) 2015 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
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   publication of this document.  Please review these documents
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   include Simplified BSD License text as described in Section 4.e of



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   the Trust Legal Provisions and are provided without warranty as
   described in the Simplified BSD License.

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
   2.  Terminology . . . . . . . . . . . . . . . . . . . . . . . . .   2
   3.  Architecture of Hierarchical SFC  . . . . . . . . . . . . . .   3
     3.1.  SFC-GW  . . . . . . . . . . . . . . . . . . . . . . . . .   5
     3.2.  Classifier for Inter-SF . . . . . . . . . . . . . . . . .   5
   4.  Encapsulation . . . . . . . . . . . . . . . . . . . . . . . .   6
     4.1.  Overlap SFC encapsulation . . . . . . . . . . . . . . . .   6
     4.2.  Metadata SFC encapsulation  . . . . . . . . . . . . . . .   6
     4.3.  Exchange SFC encapsulation  . . . . . . . . . . . . . . .   7
   5.  Coordination  . . . . . . . . . . . . . . . . . . . . . . . .   7
   6.  Summary . . . . . . . . . . . . . . . . . . . . . . . . . . .   7
   7.  Security Considerations . . . . . . . . . . . . . . . . . . .   7
   8.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   7
   9.  Information References  . . . . . . . . . . . . . . . . . . .   7
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .   8

1.  Introduction

   Service Function Chain (SFC) is the chain with a series of ordered
   Service Functions(SF).  These SFs are distributed in a DC network or
   some DC networks.  So it's common that a SFC is across several DC
   networks, which incurs the problem of DC network interconnection.
   Every part of the SFC in one DC network is a SFC within DC network.
   We call such SFC to be hierarchical SFC.  And the part of such SFC
   within a DC network is called to be Inter-SF.  Inter-SF may contain
   one or more SFs that are within one DC network, but is a logical SF
   from the view of the hierarchical SFC.

   This document is going to describe the architecture for such
   scenario.  And data plane and control plane will be provided to
   specify how the hierarchical SFC works.  Meantime, some concepts are
   proposed.

2.  Terminology

   SFC(Service Function Chain): An ordered set of some abstract SFs.

   H-SFC(Hierarchical SFC): A SFC that transfers one or more Data center
   networks.  Every Datacenter network provide a inter-SF for H-SFC.

   Inter-SF: A logical SF that is provided by a SFC in Datacenter
   network.  For H-SFC, the Inter-SF in one Datacenter network is
   regarded as a SF on the path of this H-SFC.



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   I-SFC( Internal-SFC): A Service Function Chain within the Datacenter
   network which is corresponding to the Inter-SF in H-SFC.

   SFC-GW: A gateway for SFC in Datacenter network which is used to
   interconnect with H-SFC.

3.  Architecture of Hierarchical SFC

   Hierarchical SFC is composed of an ordered of SFs or Inter-SFs.
   Inter-SF is a logic SF that is composed of an ordered of SFs which
   form a SFC in DC network.  We can connect every SFC of every
   Datacenter network as a whole H-SFC.

   For more details about H-SFC, please see Figure 1.  To setup such
   H-SFC, we need to:

   1) To deteremin what kind of service the Inter-SF should provide has
   been determined by the Orchestration;

   2) To establish the corresponding SFC in the Datacenter network of
   the Inter-SF has been established by the controller of the Datacenter
   network;

   3) Inter-SF also has its SFID in H-SFC;

   4) Inter-SF as next hop of the H-SFC also has its locator, which may
   be the address of the SFC-GW.  This locator information has been
   exchanged with Controller1.























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                                         +-------------+
                                         | Controller1 |<-------------------------------------+
                                         +-------------+                                      |
                                               ^                                              |
                                               |                                              |
           +--------------+--------------+-----+----+-------------------+                     |
           |              |                         |                   |                     |
           |              |                .........|.........            |                   |
           |         +--------------+     . +--------------+ .   +--------------+             v
           |         |     SFF1     |    .  |     SFF2     | .   |     SFF3     |     +-----------------+
           |         +--------------+    .  +--------------+ .   +--------------+     |                 |
           |              |              .         |         .          |             |  Orchestration  |
           |              |             .          |         .          |             |                 |
           v              v             .         v          .          v             +-----------------+
      +--------+     +-------------+    .   +-------------+  .    +-------------+             ^
  --->|   CF1  |---> | Inter-SF#1  |---.--> | Inter-SF#2   |--.-->| Inter-SF#3  |----->       |
      +--------+     +-------------+    .   +-------------+  .    +-------------+             |
                                         . ..................                                 |
                                                 ||                                           |
                                                 ||                                           |
                                                 ||                                           |
                                                 \/                                           |
                                        (-------------------)                                 |
                                       /   +-------------+   \                                |
                                      /    | Controller2 |<---\-------------------------------+
                                     /     +-------------+     \
                                    /             ^             )--------------------\
                          /--------(              |                                   \
                         /           +------------+----------------+---------------+   \
                        /            |                             |               |    \
                       /             v                             |               |     \
                      /  +------------------------------+          v               v      \
                     /   |  +----------+     +--------+ |      +---------+     +---------+ \
          <=============>|  |  SFC-GW  |---->|   CF2  |-|----->|  SN#21  |---->|  SN#31  |  \
                   |     |  +----------+     +--------+ |      +---------+     +---------+   \
                   |     +-------^----------------------+                           |         |
                   |             |                                                  |         |
                   |             +--------------------------------------------------+         |
                   |                               DC Network                                 |
                   (--------------------------------------------------------------------------)

                                                Figure 1 H-SFC architecture

   In the Figure 1, the Inter-SF#1, Inter-SF#2, Inter-SF#3 which is
   provided by a separate Datacenter network are an ordered set of a
   Hierarchical SFC.  For this H-SFC, it's a logical SF.  But for this
   datacenter network, it actually is a SFC within the datacenter
   network.



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   CF1 classifies the traffic and assign it a H-SFC.  The traffic
   traverses along the path according to this H-SFC.  Whenever the
   traffic enters into Inter-SF#n, it actually enters into the
   corresponding Datacenter network through SFC-GW to begin its SFC.
   The setup of this SFC in the datacenter is invisible to H-SFC.  The
   path of the SFC in the datacenter network is also invisible to H-SFC.

3.1.  SFC-GW

   SFC-GW is the component through which Inter-SF#n communicate with
   H-SFC.  For H-SFC, the SFC-GW can be considered as a SFF for the
   corresponding Inter-SF#n,see Figure 2.  And the SFC-GW's locator is
   regard as the next hope address of the HSFC.  Traffic enters into
   Inter-SF#n arrives the SFC-GW firstly.  And then the SFC-GW forwards
   the traffic to the Classifier in Datacenter network.

   When the traffic finishes this SFC in the Datacenter network, it
   should be forwarded back to SFC-GW, and then be forwarded to next SF
   or Inter-SF by the SFC-GW.

         +------------------------------+            +---------+
         |            SFC-GW            |    =======>|   SFF   |
         +------------------------------+            +---------+
                        |                                 |
                        |                                 |
                        v                                 |
         ...................................              v
         .  +------+   +------+   +------+ .          +---------+
         .  |  CF  |-->|  SF1 |-->|  SF2 | . ========>|   SF    |
         .  +------+   +------+   +------+ .          +---------+
         ...................................              ^
                       ^                                  *
                       *                                  *
                       *                                  *
                   ISFC view                          HSFC view
                            Figure 2 View of the SFC-GW

3.2.  Classifier for Inter-SF

   Classifier for Inter-SF receives the traffic from SFC-GW.  For the
   traffic, the Classifier classifies the traffic and maps the traffic
   into corresponding SFC in the Datacenter network according to the
   H-SFC header information.  The Classifier assigns the traffic the SFC
   header and the traffic is forwarded alone the SFP specified by the
   SFC header.






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4.  Encapsulation

   As description in section 3, SFC in Datacenter network is invisible
   to H-SFC.  So it's not feasible to use the forwarding method of SFC
   that is in one Datacenter network.  We need to assign a new SFC
   header for the specific SFC in the Datacenter network.

   Here is the analysis for the methods to handle the SFC in the
   Datacenter network.

4.1.  Overlap SFC encapsulation

   When the packets with H-SFC header arrives the Classifier in the
   Datacenter network, this Classifier would assign a new I-SFC header
   based on the H-SFC header.  An example is showed like the following
   format, Figure 3.

                       +------------------+
                       | Overlay Header   |
                       +------------------+
                       | I-SFC Header     |
                       +------------------+
                       | H-SFC Header     |
                       +------------------+
                       | Original Packet  |
                       +------------------+
                        Figure 3 View of the SFC-GW

   The traffic with the above 2 layer-SFC header would be forwarded
   according to the I-SFC header in the Datacenter network.  H-SFC
   header is just preserved in the packets.  At the last SFF of the
   Service Function Chain of the network, the I-SFC header is removed
   from the packet and then the packet is forwarded to the SFC-GW of the
   Datacenter network for further forwarding based on the H-SFC header.

   With such encapsulation, H-SFC information is carried along the the
   whole H-SFC life, so that the last SFF in the Datacenter center of
   the I-SFC is not required to be aware of the H-SFC.  This forwarding
   method eliminates the last SFF's awareness of the H-SFC.

4.2.  Metadata SFC encapsulation

   In this method, H-SFC header is transferred as a metadata that is
   stored in the I-SFC header.  And at the last SFF of the I-SFC, the
   SFF need to restore metadata information into H-SFC header, then pass
   such traffic to SFC-GW.





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   This method requires that the last SFF must transfer I-SFC header to
   H-SFC header before forward the traffic to SFC-GW.

4.3.  Exchange SFC encapsulation

   In this kind of encapsulation, there is 1 layer SFC header with the
   packet all the time.  The Classifier in the Datacenter network maps
   the H-SFC header to the I-SFC header.  And the last SFF of the I-SFC
   maps the I-SFC header back to H-SFC header.

   This method requires the last SFF in Datacenter networknot only map
   the I-SFC header back to H-SFC, but also must learn the mapping
   information from controller.

5.  Coordination

   To be added later.

6.  Summary

   As we discuss above, H-SFC is very useful in the Service Function
   Chain across several Datacenter networks so that the SFC is more
   scalability.  With the overlap SFC encapsulation, we keep the
   principle that the two level SFC decouple as possible as it can.  And
   we can use the existing SFC in Datacenter to be a Inter-SF without
   modification and with no new requirement for SFF.

7.  Security Considerations

   To be added later

8.  IANA Considerations

   N/A

9.  Information References

   [I-D.ietf-sfc-architecture]
              Halpern, J. and C. Pignataro, "Service Function Chaining
              (SFC) Architecture", draft-ietf-sfc-architecture-08 (work
              in progress), May 2015.

   [I-D.ietf-sfc-dc-use-cases]
              Surendra, S., Tufail, M., Majee, S., Captari, C., and S.
              Homma, "Service Function Chaining Use Cases In Data
              Centers", draft-ietf-sfc-dc-use-cases-02 (work in
              progress), January 2015.




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   [I-D.ietf-sfc-nsh]
              Quinn, P. and U. Elzur, "Network Service Header", draft-
              ietf-sfc-nsh-00 (work in progress), March 2015.

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

Authors' Addresses

   Ting Ao
   ZTE Corporation
   No.50, Ruanjian Road
   Nanjing  210012
   China

   Phone: +86 25 88016576
   Email: ao.ting@zte.com.cn


   Bo Wu
   ZTE Corporation
   No.50, Ruanjian Road
   Nanjing  210012
   China

   Email: wu.bo@zte.com.cn

























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