An MPLS-Based Forwarding Plane for Service Function Chaining
draft-ietf-mpls-sfc-02

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Last updated 2018-08-05
Replaces draft-farrel-mpls-sfc
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MPLS Working Group                                             A. Farrel
Internet-Draft                                          Juniper Networks
Intended status: Standards Track                               S. Bryant
Expires: February 6, 2019                                         Huawei
                                                                J. Drake
                                                        Juniper Networks
                                                          August 5, 2018

      An MPLS-Based Forwarding Plane for Service Function Chaining
                         draft-ietf-mpls-sfc-02

Abstract

   Service Function Chaining (SFC) is the process of directing packets
   through a network so that they can be acted on by an ordered set of
   abstract service functions before being delivered to the intended
   destination.  An architecture for SFC is defined in RFC7665.

   The Network Service Header (NSH) can be inserted into packets to
   steer them along a specific path to realize a Service Function Chain.

   Multiprotocol Label Switching (MPLS) is a widely deployed forwarding
   technology that uses labels placed in a packet in a label stack to
   identify the forwarding actions to be taken at each hop through a
   network.  Actions may include swapping or popping the labels as well,
   as using the labels to determine the next hop for forwarding the
   packet.  Labels may also be used to establish the context under which
   the packet is forwarded.

   This document describes how Service Function Chaining can be achieved
   in an MPLS network by means of a logical representation of the NSH in
   an MPLS label stack.  It does not deprecate or replace the NSH, but
   acknowledges that there may be a need for an interim deployment of
   SFC functionality in brownfield networks.

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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Farrel, et al.          Expires February 6, 2019                [Page 1]
Internet-Draft                  MPLS SFC                     August 2018

   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 February 6, 2019.

Copyright Notice

   Copyright (c) 2018 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

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Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   3
   2.  Requirements Language . . . . . . . . . . . . . . . . . . . .   4
   3.  Choice of Data Plane SPI/SI Representation  . . . . . . . . .   4
   4.  Use Case Scenarios  . . . . . . . . . . . . . . . . . . . . .   5
     4.1.  Label Swapping for Logical NSH  . . . . . . . . . . . . .   5
     4.2.  Hierarchical Encapsulation  . . . . . . . . . . . . . . .   5
     4.3.  Fine Control of Service Function Instances  . . . . . . .   6
     4.4.  Micro Chains and Label Stacking . . . . . . . . . . . . .   6
     4.5.  SFC and Segment Routing . . . . . . . . . . . . . . . . .   6
   5.  Basic Unit of Representation  . . . . . . . . . . . . . . . .   6
   6.  MPLS Label Swapping . . . . . . . . . . . . . . . . . . . . .   8
   7.  MPLS Label Stacking . . . . . . . . . . . . . . . . . . . . .  10
   8.  Mixed Mode Forwarding . . . . . . . . . . . . . . . . . . . .  12
   9.  A Note on Service Function Capabilities and SFC Proxies . . .  13
   10. Control Plane Considerations  . . . . . . . . . . . . . . . .  13
   11. Use of the Entropy Label  . . . . . . . . . . . . . . . . . .  14
   12. Metadata  . . . . . . . . . . . . . . . . . . . . . . . . . .  15
     12.1.  Indicating Metadata in User Data Packets . . . . . . . .  15
     12.2.  Inband Programming of Metadata . . . . . . . . . . . . .  17
   13. Worked Examples . . . . . . . . . . . . . . . . . . . . . . .  20
   14. Implementation Notes  . . . . . . . . . . . . . . . . . . . .  24
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