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Versions: 00 01 02 03 04 05                                             
Service Function Chaining                                       S. Homma
Internet-Draft                                                  K. Naito
Intended status: Informational                                       NTT
Expires: December 10, 2015                                   D. R. Lopez
                                                          Telefonica I+D
                                                          M. Stiemerling
                                                                NEC/H-DA
                                                               D. Dolson
                                                                Sandvine
                                                             A. Gorbunov
                                                                   Nokia
                                                              N. Leymann
                                                     Deutsche Telekom AG
                                                            June 8, 2015


          Analysis on Forwarding Methods for Service Chaining
             draft-homma-sfc-forwarding-methods-analysis-02

Abstract

   Some working groups of the IETF and other Standards Developing
   Organizations are now discussing use cases of a technology that
   enables data packets to traverse appropriate service functions
   located remotely through networks.  This is called Service Chaining
   in this document.  (Also, in Network Functions Virtualisation (NFV),
   a subject that forwarding packets to required service functions in
   appropriate order is called VNF Forwarding Graph.)  This draft does
   not focus only on SFC method, and thus, use the term "Service
   Chaining."  SFC may be one of approaches to realize Service Chaining.
   There are several Service Chaining methods to forward data packets to
   service functions, and the applicable methods will vary depending on
   the service requirements of individual networks.

   This document presents the results of analyzing packet forwarding
   methods and path selection patterns for achieving Service Chaining.
   For forwarding data packets to the appropriate service functions,
   distribution of route information and steering data packets following
   the route information, are required.  Examples of route information
   are packet identifier and the routing configurations based on the
   identifier.  Also, forwarding functions are required to decide the
   path according to the route information.

Status of This Memo

   This Internet-Draft is submitted in full conformance with the
   provisions of BCP 78 and BCP 79.




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   Copyright (c) 2015 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

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Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   3
   2.  Definition of Terms . . . . . . . . . . . . . . . . . . . . .   4
   3.  Classification of Forwarding Methods and SP Decision Patterns   5
     3.1.  Forwarding Methods  . . . . . . . . . . . . . . . . . . .   5
       3.1.1.  Method 1: Forwarding Based on Flow Identifiable
               Information . . . . . . . . . . . . . . . . . . . . .   5
       3.1.2.  Method 2: Forwarding with Stacked Transport Headers .   6
       3.1.3.  Method 3: Forwarding Based on Service Chain
               Identifiable Tags . . . . . . . . . . . . . . . . . .   8
     3.2.  Service Path Selection Patterns . . . . . . . . . . . . .   9
       3.2.1.  Pattern 1: Static Selection of End to End Service
               Path  . . . . . . . . . . . . . . . . . . . . . . . .  10
       3.2.2.  Pattern 2: Dynamic Selection of Segmented Service
               Path  . . . . . . . . . . . . . . . . . . . . . . . .  12
   4.  Consideration of Forwarding Methods and Paths Selection
       Patterns  . . . . . . . . . . . . . . . . . . . . . . . . . .  18
     4.1.  Analysis of 3.1. Forwarding Methods . . . . . . . . . . .  18
       4.1.1.  Analysis of Method 1  . . . . . . . . . . . . . . . .  18
       4.1.2.  Analysis of Method 2  . . . . . . . . . . . . . . . .  19



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       4.1.3.  Analysis of Method 3  . . . . . . . . . . . . . . . .  20
     4.2.  Analysis of 3.2. Service Paths Selection Patterns . . . .  21
       4.2.1.  Analysis of Pattern 1 . . . . . . . . . . . . . . . .  21
       4.2.2.  Analysis of Pattern 2 . . . . . . . . . . . . . . . .  22
     4.3.  Example of selecting Methods and Patterns . . . . . . . .  25
       4.3.1.  Example#1: Enterprise Datacenter Network  . . . . . .  25
       4.3.2.  Example#2: Current Mobile Service Providers Network .  26
       4.3.3.  Example#3: Fixed and Mobile Converged Service
               Providers Network . . . . . . . . . . . . . . . . . .  27
   5.  Acknowledgements  . . . . . . . . . . . . . . . . . . . . . .  28
   6.  Contributors  . . . . . . . . . . . . . . . . . . . . . . . .  28
   7.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .  29
   8.  References  . . . . . . . . . . . . . . . . . . . . . . . . .  29
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  30

1.  Introduction

   Service Chaining is a technology to provide service oriented
   forwarding which enables data packets to traverse the appropriate
   service functions deployed in networks.  This draft assumes that
   Service Chaining is achieved by the following steps:

   a. A classification function identifies data packets and determines
      the set of services that will be provided for the packets and in
      which order.

   b. The path, that the packets will traverse for reaching the required
      service functions, is established based on the result of step a.
      The paths may be established in advance.

   c. Forwarding functions determine the appropriate destination and
      forward each packet to the next hop according to the path.

   d. A service function provides services to received packets and
      return each packet to the forwarding function.

   e. Steps c and d are repeated until each packet has been transferred
      to all required service functions.

   f. After a packet has been transferred to all required Service
      Functions, it is forwarded to its original destination.

   There are several forwarding methods for Service Chaining, and they
   can be classified into certain categories in terms of distribution of
   information for setting the paths and decision of the paths.  The
   methods used to distribute the information and the patterns used to
   decide the paths will affect the mechanism of Service Chaining as
   well as service flexibility.



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   The applicable methods vary depending on network requirements, and
   thus, classifying and determining forwarding methods will be
   important in designing the architecture of Service Function Chaining
   (SFC).  This document provides the results of analyzing forwarding
   methods for Service Chaining.

   OAM, security, and redundancy are outside the scope of this draft.

2.  Definition of Terms

   Term "Classification", "Classifier" referred to
   [I-D.ietf-sfc-architecture].  Term "Service Function", "Service Node"
   referred to [I-D.ietf-sfc-dc-use-cases].

   Service Chaining:  A technology that lets data packets traverse a
      series of service functions.

   Classification:  Locally instantiated policy and customer/network/
      service profile matching of traffic flows for identification of
      appropriate outbound forwarding actions.

   Classifier (CF):  The entity that performs classification.

   Service Function (SF):  A function that is responsible for specific
      treatment of received packets.  A Service Function can act at
      various layers of a protocol stack (e.g. at the network layer or
      other OSI layers).  A Service Function can be a virtual element or
      be embedded in a physical network element.  One of multiple
      Service Functions can be embedded in the same network element.
      Multiple occurrences of the Service Function can be enabled in the
      same administrative domain.

      One or more Service Functions can be involved in the delivery of
      added-value services.  A non-exhaustive list of Service Functions
      includes: firewalls.  WAN and application acceleration, Deep
      Packet Inspection (DPI), LI (Lawful Intercept) module, server load
      balancers, NAT44 [RFC3022], NAT64 [RFC6146], NPTv6 [RFC6296],
      HOST_ID injection, HTTP Header Enrichment functions, TCP
      optimizer, etc.

   Service Node (SN):  A virtual or physical device that hosts one or
      more service functions, which can be accessed via the network
      location associated with it.

   Forwarder (FWD):  The entity, responsible for forwarding data packets
      along the service path, which includes delivery of traffic to the
      connected service functions.  FWD handles Forwarding Tables, which
      is used for forwarding packets.



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   Control Entity (CE):  The entity responsible for managing service
      topology and indicating forwarding configurations to Forwarders.

   Service Chain (SC):  A service chain defines an ordered list of
      service functions that must be applied to user packets selected as
      a result of classification.  The implied order may not be a linear
      progression as the architecture allows for nodes that copy to more
      than one branch.

   Service Path (SP):  The instantiation of a service chain in the
      network.  Packets follow a service path through the requisite
      service functions.  Service path shows a specific path of
      traversing SF instance.  For example, SC is written as SF#1 ->
      SF#2 -> SF#3 (This shows an ordered list of SFs), and SP is
      written as SF#1_1(1_1 means instance 1 of SF1) -> SF#2_1 ->
      SF#3_1.

   Service Chaining Domain (SC Domain):  The domain managed by one or a
      set of CEs.

   Service Path Information (SP Information):  The information used to
      forward packets to the appropriate SFs based on the selected
      service.  Examples of SP information include routing
      configurations for Forwarders, transport headers for forwarding
      packets to required SFs, and service/flow identifiable tags.

3.  Classification of Forwarding Methods and SP Decision Patterns

3.1.  Forwarding Methods

   In Service Chaining, data packets are transferred to service
   functions, which can be located outside the regular computed path to
   the original destination.  Therefore, a routing mechanism that is
   different from general L2/L3 switching/routing may be required.  The
   routing mechanism can be classified into three methods in terms of
   distribution of SP information and packet forwarding.

3.1.1.  Method 1: Forwarding Based on Flow Identifiable Information

   The mechanism of method 1 is shown in Figure 1.  In this method,
   routing configurations based on flow identifiable information, such
   as 5-tuple (e.g. dst IP, src IP, dst port, src port, tcp) are
   indicated to the CF and each FWD.  There may be an CE to handle this.
   The flow identifiable information can be constructed with some fields
   of L2 or L3 or combination of those.  The information can be
   configured either before packets arrive, or at the time packets
   arrive at CF and FWD.  Each FWD identifies the packets with flow
   identifiable information and forwards the packets to the SFs



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   according to the configuration.  This method does not require
   changing any fields of the original packet frame.

*Distribution model of SP information*

      +----------------+
      | Control Entity |
      +----------------+
           ^ |     indication of routing configuration
           | |           based on packet identifiable information
           | +---------------+-------------------------------+--------->
           | |               |                               |
           | |               |                               |
           | v               v                               v
       +--------+        +-------+        +------+       +-------+
------>|   CF   |------> |  FWD  |------> | SF#1 |------>|  FWD  |----->
       +--------+        +-------+        +------+       +-------+

////////////////////////////////////////////////////////////////////////
*Forwarding Tables*

Locate:     [CF]             [FWD]                           [FWD]

Table:   192.168.1.1       192.168.1.1                    192.168.1.1
          ->FWD#1           ->SF#1                         ->SF#2
         10.0.1.1          10.0.1.1                       10.0.1.1
          ->FWD#1           ->FWD#2                        ->SF#2
         ...               ...                            ...

////////////////////////////////////////////////////////////////////////
*Condition of Packet*

Locate:     [CF]             [FWD]           [SF#1]          [FWD]

         +-------+         +-------+        +-------+      +-------+
Packet:  |  PDU  |         |  PDU  |        |  PDU  |      |  PDU  |
         +-------+         +-------+        +-------+      +-------+


        Figure 1: Forwarding Based on Flow Identifiable Information

3.1.2.  Method 2: Forwarding with Stacked Transport Headers

   The mechanism of method 2 is shown in Figure 2.  In this method, the
   CF classifies packets and stacks transport headers in which actual
   network address is included, e.g., MPLS or GRE headers, onto the
   packets based on the classification.  This method does not require
   any forwarding function for forwarding packets based on the service



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   information.  Forwarding functions of underlay networks forward the
   packets to SFs following the outermost header.  The outermost header
   is removed after service process of the SF.  The actions are repeated
   until all headers are removed.

*Distribution model of SP information*

        +----------------+
        | Control Entity |
        +----------------+
            ^ |
            | |    indication of
            | |      stacking headers
            | v
         +--------+       +-------+       +------+       +------+
-------->|   CF   |------>| SF#1  |------>| SF#2 |------>| SF#3 |------>
         +--------+       +-------+       +------+       +------+

////////////////////////////////////////////////////////////////////////
*Forwarding Tables*

Locate:       [CF]

Table:    192.168.1.1           __/__/__/__/__/__/__/__/__/__/__/__/__/
           ->Stack #1,2,3       __/ Packets are forwarded to SFs by __/
          10.0.1.1              __/ the outermost transport header. __/
           ->Stack #1,3         __/__/__/__/__/__/__/__/__/__/__/__/__/
          ...

////////////////////////////////////////////////////////////////////////
*Condition of Packet*

Locate:       [CF]           [SF#1]          [SF#2]         [SF#3]

           +--------+
Header:    |To SF#1 |
           +--------+       +--------+
           |To SF#2 |       |To SF#2 |
           +--------+       +--------+     +--------+
           |To SF#3 |       |To SF#3 |     |To SF#3 |
           +--------+       +--------+     +--------+
               :                :              :              :
           +--------+       +--------+     +--------+      +--------+
Packet:    |  PDU   |       |  PDU   |     |  PDU   |      |  PDU   |
           +--------+       +--------+     +--------+      +--------+


       Figure 2: Forwarding with Stacked Multiple Transport Headers



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3.1.3.  Method 3: Forwarding Based on Service Chain Identifiable Tags

   The mechanism of this method is shown in Figure 3.  In this method, a
   CF classifies each packet and attaches a tag for identifying the
   service or flow on the packets based on the classification.  The
   routing configuration based on the tags is sent to each FWD (from
   some CE) in advance.  Each FWD forwards packets to the SFs following
   the configuration and the tag.  After a packet has traversed all SFs,
   the tag is removed and the packet is transported to the original
   destination.









































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  *Distribution model of SP information*

      +----------------+
      | Control Entity |
      +----------------+
           ^ |     indication of attached tag
           | |       and routing configuration based on tags
           | +----------------+------------------------------+--------->
           | |                |                              |
           | |                |                              |
           | v                v                              v
        +--------+        +-------+       +------+       +-------+
  ----->|   CF   |------> |  FWD  |------>| SF#1 |------>|  FWD  |----->
        +--------+        +-------+       +------+       +-------+

  //////////////////////////////////////////////////////////////////////
  *Forwarding Tables*

  Locate:  [CF]             [FWD]                          [FWD]

  Table: 192.168.1.1        IF ID#1,3                   IF ID#1,2,5
          ->Stack ID#1       ->SF#1                       ->SF#2
         10.0.1.1
          ->Stack ID#2
         ...                ...                         ...

  //////////////////////////////////////////////////////////////////////
  *Condition of Packet*

  Locate:  [CF]             [FWD]         [SF#1]           [FWD]

         +-------+        +-------+      +-------+       +-------+
  Tag:   | ID#1  |        | ID#1  |      | ID#1  |       | ID#1  |
         +-------+        +-------+      +-------+       +-------+
  Packet:|  PDU  |        |  PDU  |      |  PDU  |       |  PDU  |
         +-------+        +-------+      +-------+       +-------+


       Figure 3: Forwarding Based on Service Chain Identifiable Tags

3.2.  Service Path Selection Patterns

   Since SC contains only logical information (e.g. series of services
   that are applied to flows and their sequences), the actual instances,
   which are called SPs, are needed in order for the forwarding process
   to work.  In this process, an instance of SP is created at certain
   points during a packet's delivery.  Therefore, to forward packets,
   the SC needs to be turned into an SP, which indicates specific FWDs



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   (or switches, routers) and SFs that the packets will be forwarded to.
   From the perspective of points translating SC to SP, the methods that
   establish SPs from end to end are classified into two patterns.

3.2.1.  Pattern 1: Static Selection of End to End Service Path

   The translation point is only a CF; that is, the SP is statically
   pre-established as an end-to-end path and a CF inserts packets into
   the appropriate path based on the result of the classification.  Each
   FWD on the route has a forwarding table to uniquely determine the
   next destination of packets, and each FWD statically forwards the
   received packets to the next destination based on the table.  FWD
   requires only a function to receive indications of forwarding
   configurations from the CE.  Pattern 1 can be achieved in the
   following ways.

3.2.1.1.  SF Shared Model

   Figure 4 shows the mechanism of this model.  In this model, an SF is
   shared by multiple SPs.  Therefore, FWDs require a function to
   identify SP for each packet and insert the packets into the next
   appropriate hop.





























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 *Path Structure*

   +----+     +---+   +----+   +---+   +------+   +---+   +----+
   |    |SC#1 |FWD|   |SF#1|   |FWD|   |SF#2_1|   |FWD|   |SF#3| SP#1
   |    |==============================================================>
   |    |SC#2 |   |   |    |   |   |   +------+   |   |   |    | SP#2
   |    |============================# +------+ #======================>
   |    |     |   |   +----+   |   | # |SF#2_2| # |   |   +----+
   |    |     |   |            |   | #==========# |   |
 ->| CF |     +---+            +---+   +------+   +---+
   |    |
     .         .
     .         .
     .         .
              +---+   +----+                      +---+   +----+
   |    |SC#n |FWD|   |SF#4|                      |FWD|   |SF#5| SP#n
   |    |==============================================================>
   +----+     +---+   +----+                      +---+   +----+

                                       SC:Service Chain  SP:Service Path
 ///////////////////////////////////////////////////////////////////////
 *Packet Flow*

 Service Chain#1:
 SP#1
   [ CF ]---->[FWD]-->[SF#1]-->[FWD]-->[SF#2_1]-->[FWD]-->[SF#3]--->

 Service Chain#2:
 SP#2
   [ CF ]---->[FWD]-->[SF#1]-->[FWD]-->[SF#2_2]-->[FWD]-->[SF#3]--->
     :
 Service Chain#n:
 SP#n
   [ CF ]---->[FWD]-->[SF#4]--------------------->[FWD]-->[SF#5]--->


                         Figure 4: SF Shared Model

3.2.1.2.  SF Dedicated Model

   Figure 5 shows the mechanism of this model.  In this model, an SF
   instance (or a set of SF instances) is used by only one single SP; in
   other words, a set of SF instance is prepared for each SP.  At each
   FWD, incoming packets are statically forwarded to the single
   predefined next hop.






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  *Path Structure*

    +----+     +---+  +------+  +---+  +------+  +---+  +------+
    |    |SC#1 |FWD|  |SF#1_1|  |FWD|  |SF#2_1|  |FWD|  |SF#3_1| SP#1
    |    |=============================================================>
    |    |     +---+  +------+  +---+  +------+  +---+  +------+
    |    |     +---+  +------+  +---+  +------+  +---+  +------+
    |    |SC#2 |FWD|  |SF#1_2|  |FWD|  |SF#2_2|  |FWD|  |SF#3_2| SP#2
    |    |=============================================================>
  ->| CF |     +---+  +------+  +---+  +------+  +---+  +------+
    |    |
      .           .
      .           .
      .           .
               +---+  +------+                   +---+  +------+
    |    |SC#n |FWD|  | SF#4 |                   |FWD|  | SF#5 | SP#n
    |    |=============================================================>
    +----+     +---+  +------+                   +---+  +------+

                                       SC:Service Chain  SP:Service Path
  //////////////////////////////////////////////////////////////////////
  *How packets traverse*

  Service Chain#1:
  SP#1
    [ CF ]--->[FWD]-->[SF#1_1]->[FWD]->[SF#2_1]->[FWD]->[SF#3_1]--->

  Service Chain#2:
  SP#2
    [ CF ]--->[FWD]-->[SF#1_2]->[FWD]->[SF#2_2]->[FWD]->[SF#3_2]--->
      :
  Service Chain#n:
  SP#n
    [ CF ]--->[FWD]-->[ SF#4 ]------------------>[FWD]->[ SF#5 ]--->


                       Figure 5: SF Dedicated Model

3.2.2.  Pattern 2: Dynamic Selection of Segmented Service Path

   The mechanism of this pattern is shown in Figure 6.  The translation
   points are CFs and some FWDs.  The SP is established by a series of
   multiple paths, which are sectioned by CFs and FWDs.  The path, which
   is sectioned by CFs and FWDs, is referred to as a segmented path in
   this draft.  CFs or FWDs that select the next segmented path may
   require notification of forwarding configurations from the CE.
   Moreover, some FWDs require functions to select the destination of
   packets from various alternatives and to retrieve the information for



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   selecting the next path.  For example, each FWD obtains metric
   information or load conditions of servers and selects an optimal
   segmented path based on the information.  The CE may have the
   selection mechanism and may notify CFs or FWDs of it.


 *Path Structure*

   +----+     +---+   +----+   +---+   +------+   +---+   +----+
   |    |SC#1 |FWD|   |SF#1|   |FWD|   |SF#2_1|   |FWD|   |SF#3| SP#1
   |    |========================*=====================================>
   |    |     |   |   |    |   | # |   +------+   |   |   |    | SP#2
   |    |     |   |   |    |   | # |   +------+ #======================>
   |    |     |   |   +----+   | # |   |SF#2_2| # |   |   +----+
   |    |     |   |            | #==============# |   |
 ->| CF |     +---+            +---+   +------+   +---+
   |    |
     .         .
     .         .
     .         .
              +---+   +----+                      +---+   +----+
   |    |SC#n |FWD|   |SF#4|                      |FWD|   |SF#5| SP#m
   |    |==============================================================>
   +----+     +---+   +----+                      +---+   +----+

                                       SC:Service Chain  SP:Service Path
 ///////////////////////////////////////////////////////////////////////

 *How packets traverse*

 Service Chain#1:
 SP#1
   [ CF ]---->[FWD]-->[SF#1]-->[FWD]-->[SF#2_1]-->[FWD]-->[SF#3]--->

 SP#2
   [ CF ]---->[FWD]-->[SF#1]-->[FWD]-->[SF#2_2]-->[FWD]-->[SF#3]--->
     :
 Service Chain#n:
 SP#m
   [ CF ]---->[FWD]-->[SF#4]--------------------->[FWD]-->[SF#5]--->


           Figure 6: Dynamic Selection of Segmented Service Path

   In addition, this pattern accepts establishment of hierarchical
   domains as following:





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3.2.2.1.  Hierarchical Service Path Domains

   Complex problems often become manageable with a hierarchical
   approach.  This pattern allows network-wide orchestration of Service
   Chaining to be relatively simple, while hiding the complexities of
   fine-grained policy-based path selection within sub-domains.  Each
   sub-domain can be independently administered and orchestrated.  This
   architecture is described in [I-D.dolson-sfc-hierarchical].

   Figure 7 shows two levels of hierarchy in a service provider's
   network.  At the top level in the hierarchy, Service Chaining
   components are:

   1.  Edge-classifiers (Edge CF) that reside near the edge of a service
       provider's domain and

   2.  SF sub-domains that reside in data centers.

   3.  SF Domain Gateways that reside in data centers, linking together
       the levels of the hierarchy.  To the higher level, this is an SF.
       To the lower level, this is a classifier and FWD.






























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   *How packets traverse*

     +----+    +-----+  +----------------------+   +-----+
     |    |SC#1| FWD |  |SF Domain Gateway#1   |   | FWD |
   ->|    |================*                *=====================>
     |    |    +-----+  |  # (in DC#1)      #  |   +-----+
     |    |             |  V                #  |
     |Edge|             |+---+            +---+|   Top domain
     | CF |    * * * * *||CF | * * * * * *|FWD|| * * * * *
     |    |    *        |+---+            +-+-+|         *
     |    |    *        | | |              | | |    Sub  *
     |    |    *        +-o-o--------------o-o-+   domain*
     |    |    *   SC#1.2 | |SC#1.1        ^ ^       #1  *
     |    |    *    +-----+ |              | |           *
     |    |    *    |       V              | |           *
     |    |    *    |     +---+  +------+  | |           *
     |    |    *    |     |FWD|->|SF#1_1|--+ |           *
     |    |    *    |     +---+  +------+    |           *
     |    |    *    V                        |           *
     |    |    *  +---+  +------+  +---+  +------+       *
     |    |    *  |FWD|->|SF#1_2|->|FWD|->|SF#2_1|       *
     |    |    *  +---+  +------+  +---+  +------+       *
       .       * * * * * * * * * * * * * * * * * * * * * *
       .
     |    |    +-----+   +---------------------+     +-----+
     |    |SC#n| FWD |   | SF Domain Gateway#q |     | FWD |
     |    |=======================================================>
     |    |    +-----+   |     (in DC#m)       |     +-----+
     +----+              +---------------------+
                     (Details of sub-domain #q not shown)

       Figure 7: Service Chain Hierarchy in Service Provider Network

   The components within an SF sub-domain are opaque at the top level;
   each SF domain gateway acts as a single SF node in the top-level
   domain.  A service path in the top-level domain may visit multiple
   sub-domains.

   At the lower level in the hierarchy, each sub-domain contains an
   independently administrated Service Chaining network, generally
   comprised of multiple instances of multiple types of hosts, most
   likely (but not necessarily) within the same data center.  There is
   no need for knowledge of the "big picture" at the level of the SF-
   sub-domain except as required to forward packets to the other SFs
   that are the next hop of each chain.

   Note that different encapsulation methods can be used at each layer
   in the hierarchy, provided the SF domain-Proxy can translate between



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   them.  For example, MPLS could be used to deliver packets from
   network edge to the SF clusters within data centers, and NSH
   [I-D.ietf-sfc-nsh] could be used within the data center.

   Details of Top Level of Hierarchy

   In this pattern, referring to Figure 8, network-wide Service Chaining
   orchestration is only concerned with creating service paths from
   network edge points to sub-domains within data centers and
   configuring classifiers at a coarse level to get the correct hosts'
   traffic onto paths that will arrive at appropriate sub-domains.  The
   figure shows one possible service chain passing from edge, through
   two sub-domains, to network egress.

   This top level of orchestration may attach meta-data to provide
   context from the network edge into the data center.

                          +------------+
                          |Sub-domain#1|
                          |  in DC1    |
                          +----+-------+
                               |
                        .------+---------.   +--+
                +--+   /     /  |         \--|CF|
            --->|CF|--/---->'   |          \ +--+
                +--+ /  SC#1    |           \
                     |          |            |
                     |          |    .------>|--->
                     |         /    /        |
                     \         |   /        /
                +--+  \        |  /        /  +--+
                |CF|---\       V /        /---|CF|
                +--+    '------+---------'    +--+
                               |
                          +----+-------+
                          |Sub-domain#2|
                          |   in DC2   |
                          +------------+

           Figure 8: Network-wide view of Top Level of Hierarchy

   The orchestration at this top level must ensure bidirectional path
   symmetry so that inbound packets traverse sub-domains in the reverse
   order as outbound packets.

   Because classifiers must have rules to handle any traffic passing
   through the network, we believe that a useful approach to
   classification will be to assign traffic to service function paths on



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   the basis of coarse classification like subscriber tier, tenant or
   VRF identifier.  These classification rules could be relatively
   static, changing in response to provisioning but not in response to
   traffic.

   In some networks it might be possible to create a rule per
   residential subscriber, resulting in rule updates when subscribers
   are assigned IP addresses.  However, with judicious allocation of IP
   blocks, entire classes of subscribers could be classified with IP-
   prefix rules.  Similarly, in a mobile network path selection could be
   based on APN.

   Hence, there are methods of globally managing very large networks by
   choosing a suitable classification granularity.

   Details of Lower Level of Hierarchy

   Within each SF sub-domain, there are:

   1.  An SF domain-gateway to receive incoming data packets on any of
       the configured service chains and load-balance (if necessary)
       traffic to classifiers,

   2.  Classifier(s) to select internal service chain to use,
       potentially based on stateful flow analysis, DPI, etc.

   3.  Service components comprised of FWD and SF.

   Local Service Chaining orchestration is concerned with providing
   viable paths to various functions, providing failure recovery, NFV
   elasticity, etc.

   Classification within each sub-domain can be concerned with
   determining the local service paths for individual transport-layer
   flows based on ports, DPI and meta-data provided by the higher-level
   chain.

   For any classifier that is transport-layer-stateful, it is most
   efficient for the same classifier instance to handle traffic in both
   directions of a bidirectional connection.  State tracking may require
   that service function paths begin and end at the same node with the
   flow state, where the same classifier instance can be used for both
   directions of traffic.








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4.  Consideration of Forwarding Methods and Paths Selection Patterns

   This chapter presents the results of analyzing the forwarding methods
   and architecture patterns in chapter 3.

4.1.  Analysis of 3.1.  Forwarding Methods

4.1.1.  Analysis of Method 1

   Data Plane Aspects

      This method can achieve Service Chaining without changing packet
      format, such as attaching any header on packets, so it may not
      cause any increase in packet size or be subject to MTU
      restrictions.  Furthermore, this method does not require
      additional functions for SFs to apply or handle any header because
      data packets are transported in original format.  Therefore, it
      will be easier to use legacy SFs for network operators.

      On the other hand, it is difficult to forward a packet to same
      FWDs several times because flow identifiable information is not
      basically chainged in the forwarding processes.  For example,
      distinction of incoming ports will be required for FWD to decide
      the next hop appropriately when a packet traverse it several
      times.

   Control Plane Aspects

      This method requires FWDs to set forwarding entries for each flow.
      For example, if there are 10,000 flows to be handled at a CF/FWD,
      the forwarding table for each CF/FWD uses 10,000 flow entries at
      most.  Therefore, it might not be feasible for large-scale
      networks such as carrier networks that handle a SC per user (which
      means that individual users have their own policies), because some
      large carriers have over a million users and even more flows.
      Another concern is increase of control signaling because route
      setting is required for each flow.  Moreover, it may be hard to
      use this method if some SFs modify header fields of a packet or
      frame, for example, NAT/NAPT, in a chain.  For example, if a NAT
      changes the IP address of packets dynamically, the FWDs that
      follow need to renew their forwarding tables.

   The results of the above analysis suggest that, although this method
   is beneficial in terms of impact to existing network, it would not be
   scalable.  Therefore, this method might be suitable for networks with
   a limited number of flows.





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   Measurements taken in multiple residential service providers'
   networks indicate that for each 1Gbps of traffic the sustained rate
   of new flows can range from 1,000 flows/s to 30,000 flows/s.  From
   this, for example, there would be between 10,000 and 300,000 new
   flows/s on a 10 Gbps link.  Therefore, in some networks at some times
   of day, this method using 5-tuple as flow identifiable information
   would require sustaining up to 300,000 table updates per second for
   each FWD.  This incurs a significant amount of control traffic and
   computational effort.

4.1.2.  Analysis of Method 2

   Data Plane Aspects

      In this method, SP information is attached on each packet as
      transport headers, and the number of the headers increases
      depending on the number of SFs which the packet will traverse.
      This means that size of each packet increases.  Packet sizes may
      be restricted by the minimal available MTU of any link in the
      network and exceeding the MTU will require to fragment the
      original packets.  Fragmentation adds a new source of errors and
      may require forwarding processes to be more complex.  For example,
      the whole original packet will get discarded even if one of
      fragments of the packet gets lost, or in terms of SF equipment, it
      would be very wasteful of CPU if fragmented packets need to be
      reassembled at every SF resources, and some equipment has
      restricted resources and memory for reassembly.  Fragmentation
      will also cause an increase in traffic as more packets have to be
      processed by the network.

      Moreover, this method requires SF to be applied to the headers
      because they receive packets with optional headers.  Therefore SFs
      will be required to be able to recognize the headers, or proxy
      functions, which remove the tags before inserting packets into SFs
      and reattaches the appropriate tag on the returned packet, will be
      required.  In addition, when a SF is used by multiple SCs, it will
      be challenging for SFs to process packets because header length
      attached on each packet may vary and SFs are required to have a
      mechanism to recognize the header length for each packet.

   Control Plane Aspects

      In this method, none of the FWDs require any specific forwarding
      tables for Service Chaining or interface to receive indications of
      forwarding configuration.  Also, no CEs will be required to manage
      the forwarding configuration of FWDs, so the control plane might
      become simple.




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      On the other hand, some relay nodes such as switches or SFs are
      required to have a function to remove the outermost header from
      the received packets.  FWDs also don't have identify flow or
      service so can not change the following SPs.  Moreover, CF must
      grasp all of addresses of relay nodes which packets will traverse,
      and it will require any CE to manage addresses of relay nodes and
      a link between CF and the CE.  There are already several
      technologies proposed that can be used to achieve this method,
      such as segment routing.

   The results of the above analysis indicate that this method would be
   appropriate when the number of SFs in a SC is small, and most SFs are
   deployed in a single domain.  On the other hand, it may be unsuitable
   in cases where there are many SFs in a chain, or packets have to
   traverse multiple domains.

4.1.3.  Analysis of Method 3

   Data Plane Aspects

      In this method, a tag is defined for each SC and attached on each
      packet.  By adopting single fixed-length tag, this method can
      prevent an increase in the amount of traffic, and can provide an
      upper bound on packet size.  (Problems which happen as a result of
      exceeding MTU are stated in Section 4.1.2.)  Also, FWDs recognize
      the next hops of received packets from the tags independent of any
      information of original packets.  Therefore, SFs which modify
      original packet format can be also used.  In addition, it is easy
      to change the following SPs on a route by renewing the tag.

      On the other hand, this method requires SFs to be applied to the
      tags because SFs receive packets with the tags.  (Problems which
      happens as result of inserting packet with optional tags into SF
      are stated in Section 4.1.2) By using existing transport headers
      as the tags or outer header for forwarding, effect on network
      nodes such as existing router and switches might be restrained.

   Control Plane Aspects

      This method enables FWDs to save resources for managing forwarding
      tables and all SPs may be established in advance in most of cases.
      This prevents an increase of control signals, and also enables to
      change the following SPs without changing forwarding
      configurations of FWDs.

      On the other hand, this method requires a new control mechanism
      based on the tags, therefore, FWDs, CE and interface between them




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      have to be updated to apply forwarding configuration based on the
      tags.

   The results of the above analysis indicate that this method has many
   advantages in terms of scalability, and it might be appropriate for
   use in large-scaled networks in which there are many SFs and flows.
   By the way, if the tag handling mechanism is an entirely new
   architecture such as SFC[I-D.ietf-sfc-architecture], renewal or
   introduction of several equipment such as FWDs and CE will be
   required.

4.2.  Analysis of 3.2.  Service Paths Selection Patterns

4.2.1.  Analysis of Pattern 1

   In this pattern, the mechanism of FWDs would be simpler than the one
   in pattern 2 because FWDs do not require any functions to select
   paths or retrieve any information for determination of the next hop.
   Moreover, it is not necessary to maintain the state of each flow.
   Therefore, existing protocols for virtualizing networks, such as
   VxLAN or MPLS, can be used to achieve Service Chaining in this
   pattern.

   However, this pattern will impact the flexibility of the SCs, as
   adding new SFs to a SC, removing SFs from a SC, or migrating SFs to
   other locations requires an update or new creation of a path in the
   Service Path.  Furthermore, unified management of FWDs and SFs in an
   SC domain would be required in setting end-to-end paths.  Therefore,
   the management system of SPs, for example, a CE, for wide-area
   networks that include several segments may be massive and complex.
   Figure 9 shows the case in which SPs are established across multiple
   datacenters in pattern 1.  In Figure 9, a CE manages multiple
   datacenters as a single SC domain for establishing SPs across
   multiple datacenters.

   In pattern 4.2.1.2 (SF Dedicated Model), the number of flow entries
   that FWDs hold can be extremely small, as FWDs hold only static next-
   hop information.  Also, the CF function would be simple, as the CF
   only determines the gateway of each SP.  However, because the SF
   (instance) is settled for each SP, resource usage would be high if
   there were many SPs.










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                            +--------------+
        . . . . . . . . . . |Control Entity| . . . . .
        .         .         +--------------+         .
        .         .                                  .
   * *  . * * * * . * * * * * * * * * * * * * * * *  . * * * * * * * * *
   *    .         .                                  .                 *
   *    .         .                                  .                 *
   *    .      .-----.        .-----------.       .-----.              *
   * +----+   /  DC#1 \      /     WAN     \     /  DC#2 \             *
   * |    |=====================================================> SP#1 *
   * | CF |=====================================================> SP#2 *
   *   :                            :                              :   *
   * |    |=====================================================> SP#n *
   * +----+   \       /      \             /     \       /             *
   *           '-----'        '-----------'       '-----'              *
   *                                                                   *
   *                           SC Domain                               *
   * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * *


     Figure 9: Establishment of SPs Across Multiples DCs in Pattern 1

4.2.2.  Analysis of Pattern 2

   In this pattern, SPs are established with a combination of segmented
   paths, so it enables SPs to be established flexibly (which means, CEs
   do not need to constantly manage the entire end-to-end SP) based on
   additional information such as the load condition of SFs.

   Furthermore, as it is described in the previous section, in cases
   where some SPs traverse multiple datacenters across a WAN, SPs could
   be established with a combination of segmented paths that each
   datacenter determines independently based on the Service Chain
   information.  Therefore, it might be possible to separate SC domains
   into several small areas for WANs, which would enable a simpler
   configuration of each CE.  Figure 10 shows the case in which SPs are
   established across multiple datacenters in pattern 2.  In Figure 10,
   each CE manages a single datacenter independently, and the CEs
   synchronize the Service Chain information for establishing and
   determining the appropriate segmented SPs in each domain.

   However, the (fault) monitoring of the whole SC can get harder as
   multiple domains are part of the SC.  On the other hand, each domain
   can perform its fault management as required (and probably better as
   it is more specific).  This will require an overarching (fault)
   monitoring where information from multiple SC domains is collected
   and aggregated to get a full view of the end-to-end service of the
   SC.



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   Moreover, in this pattern, some FWDs may require additional
   mechanisms to select the next segmented path, and the FWDs must
   maintain the states of each flow because some SFs require a stateful
   process, and the FWDs need to insert packets into the same SF
   instances in the same session.

   In case that SC information is conveyed to some components via data
   plane as any encapsulation, a new protocol such as SFC
   [I-D.ietf-sfc-architecture] will be required.


                          Synchronization of
                           Service Chain info.
                 +--------------------------------------+
                 |                                      |
                 v                                      v
            +--------+                              +--------+
            |  CE#1  |                              |  CE#2  |
            +--------+                              +--------+
                 .                                      .
    * * * * * *  .  * * * * * *            * * * * * *  .  * * * * * *
    *            .            *            *            .            *
    *     .-------------.     *            *     .------------.      *
    *    /     DC#1      \    *  .------.  *    /     DC#2     \     *
    * +----+          +-----+ * /  WAN   \ * +-----+            |    *
    * |    |=========>|     | * |        | * | CF/ |==========> SP#1 *
    * | CF |=========>| FWD |===============>| FWD |==========> SP#2 *
    *   :       :        :    * |        | *    :         :       :  *
    * |    |=========>|     | * \        / * |     |==========> SP#n *
    * +----+          +-----+ *  '------'  * +-----+            |    *
    *    \               /    *            *     \             /     *
    *     '-------------'     *            *      '-----------'      *
    *       SC Domain#1       *            *      SC Domain#2        *
    * * * * * * * * * * * * * *            * * * * * * * * * * * * * *


     Figure 10: Establishment of SPs Across Multiples DCs in pattern 2

   Also, the detail analysis of establishment of "Hierarchical Service
   Path domains" is shown in the following section.

4.2.2.1.  Analysis of Hierarchical Service Path domains

   The dynamic selection of SPs pattern allows multiple independent
   domains of administration.  (In the example, two levels were shown,
   but the pattern could be extended to multiple levels.)





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   This pattern allows even the largest networks to implement SC from
   the edges of the network by using coarse-grained classification.
   Classification choices can be made that are feasible within the
   constraints of the edge classifiers and FWDs.  There is no need to
   maintain flow state or react to traffic at the top level.

   This pattern allows control of sub-domains to be delegated to
   different owners.  Each domain is simpler to comprehend than would be
   the case by dealing with a single flat network.  Furthermore,
   failures and errors are localized.  (See Figure 11.)

   +----------+
   |Top-level | . . . . . . . . . . . . . . . . . . . . .
   |Control   |                                         .
   |Entity    |          +------------+     +--------+  .
   +----------+          |sub-domain#1|. . .|  CE#1  |  .
        .                +-----+------+     +--------+  .
        .                      |                        .
        .               .------+---------.   +---+      .
        .      +---+   /                  \--|CF |. . . .
        . . . .|CF |--/                    \ |FWD|      .
        .      |FWD| /                      \+---+      .
        .      +---+ |                       |          .
        .            |                       |          .
        .            |                       |          .
        .      +---+ \                      /           .
        .      |CF |  \                    /  +---+     .
        . . . .|FWD|---\                  /---|CF | . . .
               +---+    '------+---------'    |FWD|
                               |              +---+
          +--------+     +------------+
          |  CE#2  |. . .|sub-domain#2|
          +--------+     +-----+------+

   Figure 11: Multiple Control Entities in Hierarchical Service Chaining

   This hierarchical model supports management of large networks by
   adhering to these principles:

   1.  At higher levels of hierarchy packet classification is coarse, to
       minimize state and control-plane chatter.

   2.  At lower levels of hierarchy packet classification can be more
       granular because classifiers in the lower levels deal with a
       subset of the entire network: fewer flows, lower bit-rate and a
       subset of network policy.





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   However, in this model, a new component that can proxy between the
   different domains, termed "SF Domain Gateway," will be required.  It
   has some commonality with the legacy SF proxy discussed in
   [I-D.song-sfc-legacy-sf-mapping].

   This model also requires some coordination of path information within
   the SF Domain Gateway component, since the gateway must map packets
   back and forth between domains.  Solving this probably requires
   sharing metadata dictionaries among controllers and inventing a
   scheme that provides a level of indirection by naming path
   identifiers and metadata values.

4.3.  Example of selecting Methods and Patterns

   In this section, clarifications about the most suitable method and
   pattern are made for the following example networks based on the
   results of the above analysis.

4.3.1.  Example#1: Enterprise Datacenter Network

   The conditions of the target network are as follows:

   Network type:  Network with a single DC.

   Intended service:  For providing several network service to traffic
      of one or several business offices.

   Variation of service:  A group of adopting network service varies per
      office.

   The number of SFs included in a service chain:  Less than 5 (ref.
      section 3.2.1.  Sample north-south service function chains in
      [I-D.ietf-sfc-dc-use-cases]).

   Features of SFs:  SFs are set statically, and SFs are exclusively
      used for each service.

   On the basis of the conditions "network type" and "features of SFs",
   pattern 1 with SF dedicated model would be selected.

   As the condition "variation of service" describes, such network
   requires few flow entries for each FWD, so method 1 would be
   applicable.  Method 1 also does not require SFs to have any
   additional mechanism to apply any header, thus the impact of
   implementing this method would be smaller than other methods.






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4.3.2.  Example#2: Current Mobile Service Providers Network

   The conditions of the target network are as follows:

   Network type:  Network with a single DC (e.g., (S)Gi-LAN (3GPP,
      [TS.23.203])).

   Intended service:  For providing network access service and several
      network service to traffic of millions customers.

   Variation of service:  Service varies per user or applications.

   The number of SFs included in a service chain:  Around 5(ref.
      examples of service in [I-D.ietf-sfc-use-case-mobility].).

   Features of SFs:  Many SFs are hardware equipment and they are set
      statically.  Also, many SFs are used for several service.  A
      function to inspect the user traffic in detail, such as TDF (3GPP,
      [TS.23.203]), is located around the edge of the network, and it
      might behave as a CF.

   On the basis of the conditions "network type" and "features of SFs,"
   pattern 1 with SF shared model would be selected.  In such network,
   classification based on deep packet inspection such as application
   type inspections is done, and paths branching will not be happen.

   As the other conditions describe, the operator must handle millions
   of flows and the flows traverse multiple SFs, so method 3 would be
   applicable.  Configuring such amounts of flows among large scale
   network might be too much work for operators.

   The examples of concrete service of such network are described as
   follows:

   1.  HTTP Modification

      Packet Gateway(P-GW), which is defined in 3GPP (ref. [tS.23.203]),
      detects traffic to the specific website and that traffic must be
      sent through a special element to insert additional data to the
      http header or advertisement to the HTTP traffic, so the
      destination site can apply specific deals with the operator's
      customer (simplify DRM, premium service, etc.)  That would require
      flow entries with mobile source IP, destination IP and port.

   2.  VoLTE Calls

      VoLTE calls are sent via a special SP.  The VoLTE control plane
      selects all application network elements.  But to reach



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      application network elements it fully relies on standard routing
      and switching protocols.  With Service Chaining it is possible to
      select the SP which can provide required QoS.  That would require
      to set flow entries with mobile source IP, destination IP and
      port.

   3.  Secure Internet Access

      Some customers' HTTP traffic are forwarded to one or more security
      functions to inspect for malware.  This case would require flow
      entries with source IP, destination IP and port.

   4.  Content Optimizer

      Based on the policy rules, a SC/SP with the content optimization
      might be provided.  Content optimization primarily affects video
      and HTTP traffic, and saves valuable radio resources in the
      specific radio cells during times of congestion.  A controller
      might monitor Key Performance Indicators (KPIs) of the radio
      network to detect congestion.  When congestion is detected, the
      controller might apply content optimization policy for the users
      on the congested radio cell.  Most resource-expensive traffic can
      be transcoded by a content optimizer to save bandwidth.  Selecting
      traffic for optimization would require to set flow entries with
      mobile source IP, destination IP and port.  Also, content
      optimization might require changing SCs/SPs assigned to users
      flows based on the result of KPI monitoring or the time of day.

   On the other hand, method 1 might be also selected with pattern 1
   with SF dedicated model.  For example, the series of the above
   service might be achieved by static configured flow entries, for
   example, with incoming port.  However, it will require many incoming
   ports for FWDs when the operator would like to share a SF with
   multiple SCs, and it will not be scalable.

4.3.3.  Example#3: Fixed and Mobile Converged Service Providers Network

   The conditions of the target network are as follows:

   Network type:  Network with multiple DCs (e.g., SFs are deployed at
      multiple DCs based on their applications).

   Intended service:  For providing network access service or several
      network service to traffic of millions customers.

   Variation of service:  Service varies per user.  Also, the service
      assigned to each flow might vary based on using applications.




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   The number of SFs included in a service chain:  More than 5.
      (Various service such as enriched security service and value added
      service would be provided)

   Features of SFs:  Many SFs are deployed as vNF, and some SFs are
      shared with multiple SCs.  Also, some SFs changes the following
      SPs dynamically based on the result of the process.

   On the basis of the conditions "network type" and "features of SFs,"
   pattern 2 would be selected.  Pattern 2 allows hierarchical approach
   which enables operators to deploy SFs in multiple domains easily
   based on service requirements.  For example, operators can deploy SFs
   into several domains based on application types.  This concept is
   introduced in [I-D.ietf-sfc-dc-use-cases].

   From the above conditions describe, the operator must handle enormous
   flows and paths branching, thus method 3 will be appreciable for such
   network.  Especially, security scenario sometimes requires paths
   branching based on the result of packet inspection such as processes
   of DPI or traffic analyzer.  Some security functions such as web
   application firewall (WAF) are specialized for each application, and
   it might be inefficient to insert all traffic into such SFs.
   Therefore, for inserting only target packets to appropriate security
   functions, classifying and paths branching based packet inspection
   would be required.

5.  Acknowledgements

   The authors would like to thank Konomi Mochizuki and Lily Guo for
   their reviews and comments.

6.  Contributors

   The following people are active contributors to this document and
   have provided review, content and concepts (listed alphabetically by
   surname):

   Chuong D.  Pham
   Telstra

   Hiroshi Dempo
   NEC

   Ron Parker
   Affirmed Networks

   Paul Quinn
   Cisco Systems



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7.  IANA Considerations

   This memo includes no request to IANA.

8.  References

   [I-D.dolson-sfc-hierarchical]
              Dolson, D., Homma, S., and D. Lopez, "Hierarchical Service
              Chaining", draft-dolson-sfc-hierarchical-00 (work in
              progress), May 2015.

   [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.

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

   [I-D.ietf-sfc-use-case-mobility]
              Haeffner, W., Napper, J., Stiemerling, M., Lopez, D., and
              J. Uttaro, "Service Function Chaining Use Cases in Mobile
              Networks", draft-ietf-sfc-use-case-mobility-03 (work in
              progress), January 2015.

   [I-D.song-sfc-legacy-sf-mapping]
              Song, H., You, J., Yong, L., Jiang, Y., Dunbar, L.,
              Bouthors, N., and D. Dolson, "SFC Header Mapping for
              Legacy SF", draft-song-sfc-legacy-sf-mapping-04 (work in
              progress), December 2014.

   [RFC3022]  Srisuresh, P. and K. Egevang, "Traditional IP Network
              Address Translator (Traditional NAT)", RFC 3022, January
              2001.

   [RFC6146]  Bagnulo, M., Matthews, P., and I. van Beijnum, "Stateful
              NAT64: Network Address and Protocol Translation from IPv6
              Clients to IPv4 Servers", RFC 6146, April 2011.

   [RFC6296]  Wasserman, M. and F. Baker, "IPv6-to-IPv6 Network Prefix
              Translation", RFC 6296, June 2011.



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

Authors' Addresses

   Shunsuke Homma
   NTT, Corp.
   3-9-11, Midori-cho
   Musashino-shi, Tokyo  180-8585
   Japan

   Phone: +81 422 59 3486
   Email: homma.shunsuke@lab.ntt.co.jp


   Kengo Naito
   NTT, Corp.
   3-9-11, Midori-cho
   Musashino-shi, Tokyo  180-8585
   Japan

   Email: naito.kengo@lab.ntt.co.jp


   Diego R. Lopez
   Telefonica I+D.
   Don Ramon de la Cruz,  Street
   Madrid  28006
   Spain

   Phone: +34 913 129 041
   Email: diego.r.lopez@telefonica.com


   Martin Stiemerling
   NEC Laboratories Europe / Hochschule Darmstadt
   Kurfuerstenanlage 36
   Heidelberg  69115
   Germany

   URI:   ietf.stiemerling.org










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   David Dolson
   Sandvine
   408 Albert Street
   Waterloo, Ontario  N2L 3V3
   Canada

   Email: ddolson@sandvine.com


   Alexey Gorbunov
   Nokia
   6000 Connection Drive
   Irving, Texas  75039
   USA

   Phone: +1 214 516 11 41
   Email: Alexey.gorbunov82@gmail.com


   Nicolai Leymann
   DT
   Winterfeldtstrasse 21-27
   Berlin  10781
   Germany

   Phone: +49 (0)30 835392761
   Email: n.leymann@telekom.de
























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