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Versions: (draft-napper-sfc-nsh-broadband-allocation) 00 01

Service Function Chaining                                      J. Napper
Internet-Draft                                       Cisco Systems, Inc.
Intended status: Standards Track                                S. Kumar
Expires: December 21, 2018                        Individual Contributor
                                                                P. Muley
                                                           W. Hendericks
                                                                   Nokia
                                                            M. Boucadair
                                                                  Orange
                                                           June 19, 2018


              NSH Context Header Allocation for Broadband
               draft-ietf-sfc-nsh-broadband-allocation-01

Abstract

   This document provides a recommended allocation of Network Service
   Header (NSH) context headers within the broadband service provider
   network context.  Both fixed and mobile deployments are considered.

Requirements Language

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
   document are to be interpreted as described in [RFC2119].

Status of This Memo

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

   Internet-Drafts are working documents of the Internet Engineering
   Task Force (IETF).  Note that other groups may also distribute
   working documents as Internet-Drafts.  The list of current Internet-
   Drafts is at https://datatracker.ietf.org/drafts/current/.

   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."

   This Internet-Draft will expire on December 21, 2018.








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Copyright Notice

   Copyright (c) 2018 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
   (https://trustee.ietf.org/license-info) in effect on the date of
   publication of this document.  Please review these documents
   carefully, as they describe your rights and restrictions with respect
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   include Simplified BSD License text as described in Section 4.e of
   the Trust Legal Provisions and are provided without warranty as
   described in the Simplified BSD License.

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
   2.  Terminology . . . . . . . . . . . . . . . . . . . . . . . . .   3
   3.  Network Service Header (NSH) Context Headers: A Reminder  . .   3
   4.  Recommended Context Allocation For Broadband  . . . . . . . .   4
     4.1.  MD Type 0x01 Allocation Specifics . . . . . . . . . . . .   4
     4.2.  MD Type 0x02 Allocation Specifics . . . . . . . . . . . .   6
   5.  Context Allocation and Control Plane Considerations . . . . .   7
   6.  Security Considerations . . . . . . . . . . . . . . . . . . .   7
   7.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   7
   8.  Acknowledgments . . . . . . . . . . . . . . . . . . . . . . .   7
   9.  References  . . . . . . . . . . . . . . . . . . . . . . . . .   7
     9.1.  Normative References  . . . . . . . . . . . . . . . . . .   8
     9.2.  Informative References  . . . . . . . . . . . . . . . . .   8
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .   9

1.  Introduction

   Service Function Chaining (SFC) [RFC7665] provides a mechanism for
   network traffic to be steered through an ordered list of Service
   Functions (SFs).  Furthermore, SFC allows to share metadata among
   involved SFC data functional elements (classifiers and SFs).
   Particularly, the Network Service Header (NSH, [RFC8300]) provides
   support for carrying shared metadata either using a fixed context
   header or as optional TLVs.

   This document describes a recommended default allocation scheme for
   the fixed-length context header used for SFC within fixed and mobile
   broadband service provider networks.  Also, the document defines
   companion TLV types when MD Type 0x02 is used.  The use cases
   describing the need for metadata in these deployment contexts are
   described in [I-D.ietf-sfc-use-case-mobility].



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   This document does not address control plane considerations.  The
   reader may refer to [I-D.ietf-sfc-control-plane].

2.  Terminology

   This document makes use of the terms as defined in [RFC7498],
   [RFC7665], and [RFC8300].

3.  Network Service Header (NSH) Context Headers: A Reminder

   The NSH is composed of a 4-byte base header (BH1), a 4-byte service
   path header (SH1), and a fixed 16-byte context header in the case of
   MD Type 0x01 or optional TLVs in the case of MD Type 0x02 [RFC8300].

   Figure 1 shows the format of the MD Type 0x01 NSH header.

    0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |Ver|O|U|    TTL    |   Length  |U|U|U|U|MD Type| Next Protocol | BH1
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |          Service Path Identifier              | Service Index | SH1
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                                                               |
   +                                                               +
   |                             Fixed                             |
   +                         Context Header                        +
   |                           (16 Bytes)                          |
   +                                                               +
   |                                                               |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

              Figure 1: Network Service Header (MD Type 0x01)

   Figure 2 shows the MD Type 0x02 NSH header format.

    0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |Ver|O|U|    TTL    |   Length  |U|U|U|U|MD Type| Next Protocol | BH1
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |          Service Path Identifier              | Service Index | SH1
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                                                               |
   ~              Variable Length Context Headers  (opt.)          ~
   |                                                               |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

              Figure 2: Network Service Header (MD Type 0x02)




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4.  Recommended Context Allocation For Broadband

   The following header allocations provide information to support
   service function chaining in a service provider network, for example
   as described for mobility in [I-D.ietf-sfc-use-case-mobility].

   The set of metadata headers can be delivered to SFs that can use the
   metadata within to enforce service policy, communicate between
   service functions, provide subscriber information, and other
   functionality.  Several of the headers are typed allowing for
   different metadata to be provided to different SFs or even to the
   same SF but on different packets within a flow.

   Which metadata are sent to which SFs is decided in the SFC control
   plane and is thus out of the scope of this document.

4.1.  MD Type 0x01 Allocation Specifics

   Figure 3 provides a high-level description of the fields in the
   recommended allocation of the fixed sixteen byte context header for a
   broadband context.  Each four byte word in the sixteen byte context
   header is referred to as CH1, CH2, CH3, and CH4, respectively.

    0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   | R | Sub | Tag |                 Context ID                    | CH1
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                       Sub/Endpoint ID                         ~ CH2
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   ~                   Sub/Endpoint ID (cont.)                     | CH3
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                    Service Information                        | CH4
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

                     Figure 3: NSH Context Allocation

   The intended use for each of the context header fields is as follows:

   R: MUST be set to zero upon origination, and they MUST be ignored and
      preserved unmodified by other NSH supporting elements.

   Sub:  Sub/Endpoint ID type field.  These bits determine the type of
      the 64-bit Sub/Endpoint ID field that spans CH2 and CH3.

      000:  The 64-bit Sub/Endpoint ID field is an opaque field that can
         be used or ignored by SFs as determined by the control plane.

      001:  The Sub/Endpoint ID field contains an IMSI [itu-e-164].



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      010:  The Sub/Endpoint ID field contains an MSISDN (8-15 digit)
         [itu-e-164].

      011:  The Sub/Endpoint ID field contains a 64-bit identifier that
         can be used to group flows (e.g., in Machine-to-Machine (M2M)
         contexts).

      100:  The Sub/Endpoint IP field contains a wireline subscriber ID
         in CH2, and CH3 contains the line identifier.

      101-111:  Reserved.

   Tag:  Indicates the type of the Service Information field in CH4.
      The following values are defined:

      000:  If the Tag field is not set, the Service Information field
         in CH4 is an opaque field that can be used or ignored by SFs as
         determined by the control plane.

      001:  The Service Information field in CH4 contains information
         related to the Access Network (AN) for the subscriber.  This is
         shown in Figure 4 for a 3GPP Radio Access Network (RAN).

         Note that these values should correspond to those that can be
         obtained for the flow from the corresponding 3GPP PCRF (Policy
         and Charging Rules Function) component using Diameter as
         described in [TS.29.230].

    0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   | CAN |    QoS/DSCP   | Con |          App Id         |  Rsvd   | CH4
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

               Figure 4: Service Information RAN Allocation

         CAN:  IP-CAN-Type for IP Connectivity Access Network (Diameter
            AVP code 1027).

         QoS:  QoS-Class-Identifier AVP (Diameter AVP code 1028) or
            Differentiated Services Code Point (DSCP) marking as
            described in [RFC2474].

         Con:  Access congestion level.  An Access Congestion level
            '000' means an unknown/undefined congestion level.  An
            Access Congestion level '001' means no congestion.  For
            other values of Access Congestion level, a higher value
            indicates a higher level of congestion.




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         App Id:  Application ID describing the flow type.  Allocation
            of IDs is done using the control plane and is out of the
            scope of this document.

         Rsvd:  Reserved.

      010-111:  Reserved.

   Context ID:  The Context ID field allows the Sub/Endpoint ID field to
      be scoped.  For example, the Context ID field may contain the
      incoming VRF, VxLAN VNID, VLAN, or a policy identifier within
      which the Sub/Endpoint ID field is defined.

   Sub/Endpoint ID:  64-bit length Subscriber/Endpoint identifier (e.g.,
      IMSI, MSISDN, or implementation-specific Endpoint ID) of the
      corresponding subscriber/machine/application for the flow.

   Service Information:  The Service Information field is a unique
      identifier that can carry metadata specific to the flow or
      subscriber identified in the Sub/Endpoint ID field.

4.2.  MD Type 0x02 Allocation Specifics

   Figure 5 depictes the format of the recommended allocation of the
   variable length headers for a mobility context.

    0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |     TLV Class = 3GPP          |C|    Type     |U|U|U|   Len   |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |    Data ...
   +-+-+-+-+-+-+-+-+

                         Figure 5: TLV Allocation

   The intended use of the header is for TLVs associated with 3GPP Radio
   Access Networks as described in [TS.29.230].  This TLV can be used by
   3GPP to extend the metadata as per use cases.  Having this TLV helps
   to carry more information that does not fit within the MD Type 0x01.

   The Len field carries the total length.  Type = 0x01 is reserved.  If
   set to 0x01, the TLV carries the 4 context headers as defined in
   Section 4.1.








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5.  Context Allocation and Control Plane Considerations

   This document describes an allocation scheme for both the fixed
   context header (MD Type#1) and optional TLV headers (MD Type#2) in
   the context of broadband service providers.  This allocation of
   headers should be considered as a guideline and may vary depending on
   the use case.

   The control plane aspects of specifying and distributing the
   allocation scheme among different SFs within the Service Function
   Chaining environment to guarantee consistent semantics for the
   metadata is beyond the scope of this document.

6.  Security Considerations

   This specification relies on NSH to share metadata among SFC data
   plane elements.  Security-related consideration discussed in
   [RFC8300] MUST be followed.

   The recommended header allocation in this document includes sensitive
   information that MUST NOT be revealed outside an SFC-enabled domain.
   Those considerations are already discussed in [RFC8300].  NSH allows
   by design to remove any NSH data before existing an SFC-enabled
   domain.

   Furthermore, means to prevent that illegitimate nodes insert spoofed
   data MUST be supported.  As a reminder, the NSH specification assumes
   ingress boundary nodes strip any NSH data that may be present in a
   packet.  Misbehaving nodes from within an SFC-enabled domain may
   alter the content of the NSH data.  Such treats are discussed in
   [RFC8300].  This document does not introduce new treats compared to
   those discussed in [RFC8300].

7.  IANA Considerations

   This document requests IANA to assign a TLV class for 3GPP to be used
   for its use cases.

8.  Acknowledgments

   The authors would like to thank Jim Guichard for his assistance
   structuring the document.

9.  References







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9.1.  Normative References

   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119,
              DOI 10.17487/RFC2119, March 1997,
              <https://www.rfc-editor.org/info/rfc2119>.

   [RFC7665]  Halpern, J., Ed. and C. Pignataro, Ed., "Service Function
              Chaining (SFC) Architecture", RFC 7665,
              DOI 10.17487/RFC7665, October 2015,
              <https://www.rfc-editor.org/info/rfc7665>.

   [RFC8300]  Quinn, P., Ed., Elzur, U., Ed., and C. Pignataro, Ed.,
              "Network Service Header (NSH)", RFC 8300,
              DOI 10.17487/RFC8300, January 2018,
              <https://www.rfc-editor.org/info/rfc8300>.

9.2.  Informative References

   [I-D.ietf-sfc-control-plane]
              Boucadair, M., "Service Function Chaining (SFC) Control
              Plane Components & Requirements", draft-ietf-sfc-control-
              plane-08 (work in progress), October 2016.

   [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-08 (work in
              progress), May 2018.

   [itu-e-164]
              "The international public telecommunication numbering
              plan", ITU-T E.164, November 2010.

   [RFC2474]  Nichols, K., Blake, S., Baker, F., and D. Black,
              "Definition of the Differentiated Services Field (DS
              Field) in the IPv4 and IPv6 Headers", RFC 2474,
              DOI 10.17487/RFC2474, December 1998,
              <https://www.rfc-editor.org/info/rfc2474>.

   [RFC7498]  Quinn, P., Ed. and T. Nadeau, Ed., "Problem Statement for
              Service Function Chaining", RFC 7498,
              DOI 10.17487/RFC7498, April 2015,
              <https://www.rfc-editor.org/info/rfc7498>.

   [TS.29.230]
              "Diameter applications; 3GPP specific codes and
              identifiers", 3GPP TS 29.230 14.5.0, July 2017.



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Authors' Addresses

   Jeffrey Napper
   Cisco Systems, Inc.

   Email: jenapper@cisco.com


   Surendra Kumar
   Individual Contributor

   Email: surendra.stds@gmail.com


   Praveen Muley
   Nokia

   Email: praveen.muley@nokia.com


   Wim Hendericks
   Nokia

   Email: Wim.Henderickx@nokia.com


   Mohamed Boucadair
   Orange
   France

   Email: mohamed.boucadair@orange.com




















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