Network Service Header Metadata Type 2 Variable-Length Context Headers
draft-ietf-sfc-nsh-tlv-09

Document Type Active Internet-Draft (sfc WG)
Authors Yuehua Wei  , Uri Elzur  , Sumandra Majee  , Carlos Pignataro  , Donald Eastlake 
Last updated 2021-11-18 (latest revision 2021-10-11)
Stream Internet Engineering Task Force (IETF)
Intended RFC status Proposed Standard
Formats plain text pdf htmlized bibtex
Reviews
Stream WG state Submitted to IESG for Publication
Document shepherd Greg Mirsky
Shepherd write-up Show (last changed 2021-09-01)
IESG IESG state IESG Evaluation
Action Holders
Martin Vigoureux  for 29 days
Consensus Boilerplate Yes
Telechat date On agenda of 2021-12-02 IESG telechat
Has 2 DISCUSSes. Needs 7 more YES or NO OBJECTION positions to pass.
Responsible AD Martin Vigoureux
Send notices to gregimirsky@gmail.com
IANA IANA review state IANA OK - Actions Needed
SFC                                                          Y. Wei, Ed.
Internet-Draft                                           ZTE Corporation
Intended status: Standards Track                                U. Elzur
Expires: April 14, 2022                                            Intel
                                                                S. Majee
                                                  Individual contributor
                                                            C. Pignataro
                                                                   Cisco
                                                             D. Eastlake
                                                  Futurewei Technologies
                                                        October 11, 2021

 Network Service Header Metadata Type 2 Variable-Length Context Headers
                       draft-ietf-sfc-nsh-tlv-09

Abstract

   Service Function Chaining (SFC) uses the Network Service Header (NSH)
   (RFC 8300) to steer and provide context Metadata (MD) with each
   packet.  Such Metadata can be of various Types including MD Type 2
   variable length context headers.  This document specifies several
   such context headers that can be used within a service function path.

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 April 14, 2022.

Copyright Notice

   Copyright (c) 2021 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

Wei, et al.              Expires April 14, 2022                 [Page 1]
Internet-Draft           NSH MD2 Context Headers            October 2021

   (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
   to this document.  Code Components extracted from this document must
   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.  Conventions used in this document . . . . . . . . . . . . . .   3
     2.1.  Terminology . . . . . . . . . . . . . . . . . . . . . . .   3
     2.2.  Requirements Language . . . . . . . . . . . . . . . . . .   3
   3.  NSH MD Type 2 format  . . . . . . . . . . . . . . . . . . . .   3
   4.  NSH MD Type 2 Context Headers . . . . . . . . . . . . . . . .   4
     4.1.  Forwarding Context  . . . . . . . . . . . . . . . . . . .   4
     4.2.  Tenant Identifier . . . . . . . . . . . . . . . . . . . .   6
     4.3.  Ingress Network Node Information  . . . . . . . . . . . .   6
     4.4.  Ingress Network Source Interface  . . . . . . . . . . . .   7
     4.5.  Flow ID . . . . . . . . . . . . . . . . . . . . . . . . .   7
     4.6.  Source and/or Destination Groups  . . . . . . . . . . . .   8
     4.7.  Policy Identifier . . . . . . . . . . . . . . . . . . . .   8
   5.  Security Considerations . . . . . . . . . . . . . . . . . . .   9
   6.  Acknowledgments . . . . . . . . . . . . . . . . . . . . . . .   9
   7.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   9
     7.1.  Forwarding Context Types  . . . . . . . . . . . . . . . .  10
   8.  References  . . . . . . . . . . . . . . . . . . . . . . . . .  10
     8.1.  Normative References  . . . . . . . . . . . . . . . . . .  10
     8.2.  Informative References  . . . . . . . . . . . . . . . . .  11
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  12

1.  Introduction

   The Network Service Header (NSH) [RFC8300] is the Service Function
   Chaining (SFC) encapsulation that supports the SFC architecture
   [RFC7665].  As such, the NSH provides following key elements:

   1.  Service Function Path(SFP) identification.

   2.  Indication of location within a Service Function Path.

   3.  Optional, per-packet metadata (fixed-length or variable-length).

   [RFC8300] further defines two metadata formats (MD Types): 1 and 2.
   MD Type 1 defines the fixed-length, 16-octet long metadata, whereas
   MD Type 2 defines a variable-length context format for metadata.
   This document defines serveral common metadata context headers for

Wei, et al.              Expires April 14, 2022                 [Page 2]
Internet-Draft           NSH MD2 Context Headers            October 2021

   use with NSH MD Type 2.  These supplement the Subscriber Identity and
   Performance Policy MD Type 2 metadata context headers specified in
   [RFC8979].

   This document does not address metadata usage, updating/chaining of
   metadata, or other SFP functions.  Those topics are described in
   [RFC8300].

2.  Conventions used in this document

2.1.  Terminology

   This document uses the terminology defined in the SFC Architecture
   [RFC7665] and the Network Service Header [RFC8300].

2.2.  Requirements Language

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
   "OPTIONAL" in this document are to be interpreted as described in BCP
   14 [RFC2119] [RFC8174] when, and only when, they appear in all
   capitals, as shown here.

3.  NSH MD Type 2 format

   An NSH is composed of a 4-octet Base Header, a 4-octet Service Path
   Header and optional Context Headers.  The Base Header identifies the
   MD-Type in use:

    0                   1                   2                   3
    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 |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

                         Figure 1: NSH Base Header

   Please refer to NSH [RFC8300] for a detailed header description.

   When the base header specifies MD Type = 0x2, zero or more Variable
   Length Context Headers MAY be added, immediately following the
   Service Path Header.  Figure 2 below depicts the format of the
   Context Header as defined in Section 2.5.1 of [RFC8300].

Wei, et al.              Expires April 14, 2022                 [Page 3]
Internet-Draft           NSH MD2 Context Headers            October 2021

        0                   1                   2                   3
        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
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |          Metadata Class       |      Type     |U|    Length   |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |                   Variable-Length Metadata                    |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

               Figure 2: NSH Variable-Length Context Headers

4.  NSH MD Type 2 Context Headers

   [RFC8300] specifies Metadata Class 0x0000 as IETF Base NSH MD Class.
   In this document, metadata types are defined for the IETF Base NSH MD
   Class.

4.1.  Forwarding Context

   This metadata context carries a network forwarding context, used for
   segregation and forwarding scope.  Forwarding context can take
   several forms depending on the network environment.  For example,
   VXLAN/VXLAN-GPE VNID, VRF identification, or VLAN.

        0                   1                   2                   3
        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
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |    Metadata Class = 0x0000    |  Type = TBA1  |U|  Length = 4 |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |CT=0x0 |             Reserved          |        VLAN ID        |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

                     Figure 3: Forwarding Context - 1

        0                   1                   2                   3
        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
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |    Metadata Class = 0x0000    |  Type = TBA1  |U|  Length = 4 |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |CT=0x1 |Resv   |     Service VLAN ID   |    Customer VLAN ID   |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

                     Figure 4: Forwarding Context - 2

Wei, et al.              Expires April 14, 2022                 [Page 4]
Internet-Draft           NSH MD2 Context Headers            October 2021

        0                   1                   2                   3
        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
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |    Metadata Class = 0x0000    |  Type = TBA1  |U|  Length = 4 |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |CT=0x2 |   Reserved    |              MPLS VPN Label           |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

                     Figure 5: Forwarding Context - 3

        0                   1                   2                   3
        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
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |    Metadata Class = 0x0000    |  Type = TBA1  |U|  Length = 4 |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |CT=0x3 | Resv  |            Virtual Network Identifier         |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

                     Figure 6: Forwarding Context - 4

        0                   1                   2                   3
        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
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |    Metadata Class = 0x0000    |  Type = TBA1  |U|  Length = 8 |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |CT=0x4 |             Reserved                                  |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |                            Session ID                         |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

                     Figure 7: Forwarding Context - 5

   where:

      Context Type (CT) is four bits-long field that defines the length
      and the interpretation of the Forwarding Context field.  Please
      see the IANA Considerations in Section 7.  This document defines
      these CT values:

         0x0 - 12 bits VLAN identifier.  See Figure 3.  Reserved bits
         MUST be sent as zero and ignored on receipt

         0x1 - 24 bits double tagging identifiers.  A service VLAN tag
         followed by a customer VLAN tag [IEEE.802.1Q_2018].  The two
         VLAN IDs are concatenated and appear in the same order that
         they appeared in the payload.  See Figure 4.  Reserved bits
         MUST be sent as zero and ignored on receipt

Wei, et al.              Expires April 14, 2022                 [Page 5]
Internet-Draft           NSH MD2 Context Headers            October 2021

         0x2 - 20 bits MPLS VPN label.  See Figure 5.  Reserved bits
         MUST be sent as zero and ignored on receipt

         0x3 - 24 bits virtual network identifier (VNI).  See Figure 6.
         Reserved bits MUST be sent as zero and ignored on receipt

         0x4 - 32 bits Session ID ([RFC3931]).  This is called Key in
         GRE [RFC2890].  See Figure 7.

4.2.  Tenant Identifier

   Tenant identification is often used for segregation within a multi-
   tenant environment.  Orchestration system-generated tenant IDs are an
   example of such data.  This context header carries both the format
   and value of the Tenant identifier.

       0                   1                   2                   3
       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
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |    Metadata Class = 0x0000    |  Type = TBA2  |U| Length = var|
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      ~                         Tenant ID                             ~
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

                     Figure 8: Tenant Identifier List

   The fields are described as follows:

      Length: Indicates the length of the Tenant ID in bytes (see
      Section 2.5.1 of [RFC8300]).

      Tenant ID: Represents an opaque value pointing to Orchestration
      system-generated tenant identifier.  The structure and semantics
      of this field are deployment specific.

4.3.  Ingress Network Node Information

   This context header carries a Node ID of the ingress network node.

       0                   1                   2                   3
       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
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |    Metadata Class = 0x0000    |  Type = TBA3  |U| Length = var|
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      ~                        Node ID                                ~
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

                     Figure 9: Ingress Network Node ID

Wei, et al.              Expires April 14, 2022                 [Page 6]
Internet-Draft           NSH MD2 Context Headers            October 2021

   The fields are described as follows:

      Length: Indicates the length of the Node ID in bytes (see
      Section 2.5.1 of [RFC8300]).

      Node ID: Represents an opaque value of the ingress network node
      ID.  The structure and semantics of this field are deployment
      specific.  For example, Node ID may be a 4 bytes IPv4 address Node
      ID, or a 16 bytes IPv6 address Node ID, or a 6 bytes MAC address,
      or 8 bytes MAC address (EUI-64), etc,.

4.4.  Ingress Network Source Interface

   This context identifies the ingress interface of the ingress network
   node.  This is an opaque quantity to the NSH.

       0                   1                   2                   3
       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
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |    Metadata Class = 0x0000    |  Type = TBA4  |U| Length = var|
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      ~                     Source Interface                          ~
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

                Figure 10: Ingress Network Source Interface

   The fields are described as follows:

      Length: Indicates the length of the Source Interface in bytes (see
      Section 2.5.1 of [RFC8300]).

      Source Interface: Identifier of the ingress interface of the
      ingress network node.

4.5.  Flow ID

   Flow ID provides a field in the NSH MD Type 2 to label packets
   belonging to the same flow.  Absence of this field, or a value of
   zero denotes that packets have not been labeled.

Wei, et al.              Expires April 14, 2022                 [Page 7]
Internet-Draft           NSH MD2 Context Headers            October 2021

       0                   1                   2                   3
       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
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |    Metadata Class = 0x0000    |  Type = TBA5  |U| Length = 4  |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                     Flow ID                                   |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

                            Figure 11: Flow ID

   The fields are described as follows:

      Length: Indicates the length of the Flow ID in bytes (see
      Section 2.5.1 of [RFC8300]).  [RFC6437] defined IPv6 Flow Label as
      a 20-bit long unsigned integer.  Also, [RFC6790], which defined
      the use of an entropy label in the MPLS network, is 20-bit long.

      Flow ID: Represents an opaque value of the Flow ID.  The Flow ID
      is right justified (appears in the least significant bits of the
      Flow ID word) and is padded on the left with bits which MUST be
      sent as zero and ignored on receipt.

4.6.  Source and/or Destination Groups

   Intent-based systems can use this data to express the logical
   grouping of source and/or destination objects.  [GROUPBASEDPOLICY]
   and [GROUPPOLICY] provide examples of such a system.  Each is
   expressed as a 32-bit opaque object.

       0                   1                   2                   3
       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
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |    Metadata Class = 0x0000    |  Type = TBA6  |U|  Length=8   |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                        Source Group                           |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                        Dest Group                             |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

                       Figure 12: Source/Dest Groups

4.7.  Policy Identifier

   Traffic handling policies are often referred to by a system-generated
   identifier, which is then used by the devices to look up the policy's
   content locally.  For example, this identifier could be an index to
   an array, a lookup key, a database Id.  The identifier allows

Wei, et al.              Expires April 14, 2022                 [Page 8]
Internet-Draft           NSH MD2 Context Headers            October 2021

   enforcement agents or services to look up the content of their part
   of the policy quite efficiently.

       0                   1                   2                   3
       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
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |    Metadata Class = 0x0000    |  Type = TBA7  |U|  Length=var |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      ~                     Policy ID                                 ~
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

                           Figure 13: Policy ID

   The fields are described as follows:

      Length: Indicates the length of the Policy ID in bytes (see
      Section 2.5.1 of [RFC8300]).

      Policy ID: Represents an opaque value of the Policy ID.

   This policy identifier is a general policy ID, essentially a key to
   allow Service Functions to know which policies to apply to packets.
   Those policies generally will not have much to do with performance,
   but rather with what specific treatment to apply.  It may for example
   select a URL filter data set for a URL filter, or select a video
   transcoding policy in a transcoding SF.  The Performance Policy
   Identifier in [RFC8979] is described there as having very specific
   use, and for example says that fully controlled SFPs would not use
   it.  The Policy ID in this document is for cases not covered by
   [RFC8979].

5.  Security Considerations

   [RFC8300] describes the general security considerations for
   protecting NSH.  [I-D.ietf-sfc-nsh-integrity] specifies methods of
   protecting NSH metadata.

6.  Acknowledgments

   The authors would like to thank Paul Quinn, Behcet Sarikaya, Dirk von
   Hugo, Mohamed Boucadair, Gregory Mirsky, Joel Halpern for providing
   invaluable concepts and content for this document.

7.  IANA Considerations

   IANA is requested to assign the following types from the "NSH IETF-
   Assigned Optional Variable-Length Metadata Types" (0x0000 IETF Base
   NSH MD Class) registry available at [IANA-NSH-MD2]:

Wei, et al.              Expires April 14, 2022                 [Page 9]
Internet-Draft           NSH MD2 Context Headers            October 2021

   This document defines the following new values (Table 1) in the
   Network Service Header (NSH) metadata context Type registry:

       +-------+----------------------------------+---------------+
       | Value |           Description            | Reference     |
       +-------+----------------------------------+---------------+
       | TBA1  |        Forwarding Context        | This document |
       | TBA2  |        Tenant Identifier         | This document |
       | TBA3  |      Ingress Network NodeID      | This document |
       | TBA4  |    Ingress Network Interface     | This document |
       | TBA5  |             Flow ID              | This document |
       | TBA6  | Source and/or Destination Groups | This document |
       | TBA7  |        Policy Identifier         | This document |
       +-------+----------------------------------+---------------+

                           Table 1: Type Values

7.1.  Forwarding Context Types

   IANA is requested to create a new sub-registry for "Forwarding
   Context" context types at [IANA-NSH-MD2] as follows:

   The Registration Policy is IETF Review

   +---------+-----------------------------------------+---------------+
   | Value   |     Forwarding Context Header Types     | Reference     |
   +---------+-----------------------------------------+---------------+
   | 0x0     |          12-bit VLAN identifier         | This document |
   | 0x1     |    24-bit double tagging identifiers    | This document |
   | 0x2     |          20-bit MPLS VPN label          | This document |
   | 0x3     | 24-bit virtual network identifier (VNI) | This document |
   | 0x4     |            32-bit Session ID            | This document |
   | 0x5-0xE |                Unassigned               |               |
   | 0xF     |                 Reserved                | This document |
   +---------+-----------------------------------------+---------------+

                     Table 2: Forwarding Context Types

8.  References

8.1.  Normative References

   [I-D.ietf-sfc-nsh-integrity]
              Boucadair, M., Reddy, T., and D. Wing, "Integrity
              Protection for the Network Service Header (NSH) and
              Encryption of Sensitive Context Headers", draft-ietf-sfc-
              nsh-integrity-09 (work in progress), September 2021.

Wei, et al.              Expires April 14, 2022                [Page 10]
Internet-Draft           NSH MD2 Context Headers            October 2021

   [IANA-NSH-MD2]
              IANA, "NSH IETF-Assigned Optional Variable-Length Metadata
              Types", <https://www.iana.org/assignments/nsh/
              nsh.xhtml#optional-variable-length-metadata-types>.

   [IEEE.802.1Q_2018]
              IEEE, "IEEE Standard for Local and Metropolitan Area
              Networks--Bridges and Bridged Networks", July 2018,
              <http://ieeexplore.ieee.org/servlet/
              opac?punumber=8403925>.

   [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>.

   [RFC3931]  Lau, J., Ed., Townsley, M., Ed., and I. Goyret, Ed.,
              "Layer Two Tunneling Protocol - Version 3 (L2TPv3)",
              RFC 3931, DOI 10.17487/RFC3931, March 2005,
              <https://www.rfc-editor.org/info/rfc3931>.

   [RFC8174]  Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
              2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
              May 2017, <https://www.rfc-editor.org/info/rfc8174>.

   [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>.

8.2.  Informative References

   [GROUPBASEDPOLICY]
              OpenStack, "Group Based Policy", 2014.

   [GROUPPOLICY]
              OpenDaylight, "Group Policy", 2014.

   [RFC2890]  Dommety, G., "Key and Sequence Number Extensions to GRE",
              RFC 2890, DOI 10.17487/RFC2890, September 2000,
              <https://www.rfc-editor.org/info/rfc2890>.

   [RFC6437]  Amante, S., Carpenter, B., Jiang, S., and J. Rajahalme,
              "IPv6 Flow Label Specification", RFC 6437,
              DOI 10.17487/RFC6437, November 2011,
              <https://www.rfc-editor.org/info/rfc6437>.

Wei, et al.              Expires April 14, 2022                [Page 11]
Internet-Draft           NSH MD2 Context Headers            October 2021

   [RFC6790]  Kompella, K., Drake, J., Amante, S., Henderickx, W., and
              L. Yong, "The Use of Entropy Labels in MPLS Forwarding",
              RFC 6790, DOI 10.17487/RFC6790, November 2012,
              <https://www.rfc-editor.org/info/rfc6790>.

   [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>.

   [RFC8979]  Sarikaya, B., von Hugo, D., and M. Boucadair, "Subscriber
              and Performance Policy Identifier Context Headers in the
              Network Service Header (NSH)", RFC 8979,
              DOI 10.17487/RFC8979, February 2021,
              <https://www.rfc-editor.org/info/rfc8979>.

Authors' Addresses

   Yuehua Wei (editor)
   ZTE Corporation
   No.50, Software Avenue
   Nanjing  210012
   China

   Email: wei.yuehua@zte.com.cn

   Uri Elzur
   Intel

   Email: uri.elzur@intel.com

   Sumandra Majee
   Individual contributor

   Email: Sum.majee@gmail.com

   Carlos Pignataro
   Cisco

   Email: cpignata@cisco.com

Wei, et al.              Expires April 14, 2022                [Page 12]
Internet-Draft           NSH MD2 Context Headers            October 2021

   Donald E. Eastlake
   Futurewei Technologies

   Email: d3e3e3@gmail.com

Wei, et al.              Expires April 14, 2022                [Page 13]