Network Working Group                                              Z. Li
Internet-Draft                                                   J. Dong
Intended status: Standards Track                     Huawei Technologies
Expires: 8 September 2022                                   7 March 2022


      Carrying Virtual Transport Network Identifier in MPLS Packet
                  draft-li-mpls-enhanced-vpn-vtn-id-02

Abstract

   A Virtual Transport Network (VTN) is a virtual network which has a
   customized network topology and a set of dedicated or shared network
   resources allocated from the underlying network infrastructure.
   Multiple VTNs can be created by network operator for using as the
   underlay for one or a group of VPNs services to provide enhanced VPN
   (VPN+) services.  In packet forwarding, some fields in the data
   packet needs to be used to identify the VTN the packet belongs to, so
   that the VTN-specific processing can be executed.  In the context of
   network slicing, a VTN can be instantiated as a Network Resource
   Partition (NRP).

   This document proposes a mechanism to carry the VTN-ID in an MPLS
   packet to identify the VTN the packet belongs to.  The procedure for
   processing the VTN ID is also specified.

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
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   Drafts is at https://datatracker.ietf.org/drafts/current/.

   Internet-Drafts are draft documents valid for a maximum of six months
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   time.  It is inappropriate to use Internet-Drafts as reference
   material or to cite them other than as "work in progress."

   This Internet-Draft will expire on 8 September 2022.

Copyright Notice

   Copyright (c) 2022 IETF Trust and the persons identified as the
   document authors.  All rights reserved.




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   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
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   provided without warranty as described in the Revised BSD License.

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
   2.  Requirements Language . . . . . . . . . . . . . . . . . . . .   3
   3.  Carrying VTN Information in MPLS Packet . . . . . . . . . . .   3
   4.  Procedures  . . . . . . . . . . . . . . . . . . . . . . . . .   5
     4.1.  VTN Header Insertion  . . . . . . . . . . . . . . . . . .   5
     4.2.  VTN based Packet Forwarding . . . . . . . . . . . . . . .   5
   5.  Capability Advertisement and Negotiation  . . . . . . . . . .   6
   6.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   6
   7.  Security Considerations . . . . . . . . . . . . . . . . . . .   6
   8.  Contributors  . . . . . . . . . . . . . . . . . . . . . . . .   6
   9.  Acknowledgements  . . . . . . . . . . . . . . . . . . . . . .   7
   10. References  . . . . . . . . . . . . . . . . . . . . . . . . .   7
     10.1.  Normative References . . . . . . . . . . . . . . . . . .   7
     10.2.  Informative References . . . . . . . . . . . . . . . . .   7
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .   8

1.  Introduction

   Virtual Private Networks (VPNs) provide different groups of users
   with logically isolated connectivity over a common shared network
   infrastructure.  With the introduction of 5G, new service types may
   require connectivity services with advanced characteristics comparing
   to traditional VPNs, such as strict isolation from other services or
   guaranteed performance.  These services are refered to as "enhanced
   VPNs" (VPN+).  [I-D.ietf-teas-enhanced-vpn] describes a framework and
   candidate component technologies for providing VPN+ services.

   The enhanced properties of VPN+ require integration between the
   overlay connectivity and the characteristics provided by the underlay
   network.  To meet the requirement of enhanced VPN services, a number
   of Virtual Transport Networks (VTNs) need to be created, each
   consists of a subset of the underlay network topology and a set of
   network resources allocated from the underlay network to meet the
   requirement of one or a group of VPN+ services.  In the network,
   traffic of different VPN+ services may to be processed separately
   based on the topology and the network resources associated with the
   corresponding VTN.  [I-D.ietf-teas-ietf-network-slices] introduces



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   the concept Network Resource Partition (NRP) as a set of network
   resources that are available to carry traffic and meet the SLOs and
   SLEs.  In the context of network slicing, a VTN can be instantiated
   as a Network Resource Partition (NRP).

   For network scenarios where a large number of VTNs need to be created
   and maintained, [I-D.dong-teas-nrp-scalability] describes the
   scalability considerations for VTN.  One approach to improve the data
   plane scalability is introducing a dedicated VTN Identifier (VTN-ID)
   in data packets to identify the VTN the packets belong to, so that
   VTN-specific packet processing can be performed by network nodes.

   This document proposes a mechanism to carry the VTN Identifier (VTN-
   ID) and the related information in MPLS [RFC3031] data packets, so
   that the packet will be processed by network nodes using the set of
   network resources allocated to the corresponding VTN.  The procedure
   for processing the VTN-ID is also specified.  The forwarding path of
   the MPLS LSP is determined using the MPLS label stack in the packet,
   and the set of local network resources used for processing the packet
   is determined by the VTN-ID.  The mechanism introduced in this
   document is applicable to both MPLS networks with RSVP-TE [RFC3209]
   or LDP [RFC5036] LSPs, and MPLS networks with Segment Routing (SR)
   [RFC8402] [RFC8660].

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
   BCP14 RFC 2119 [RFC2119] RFC 8174 [RFC8174] when, and only when, they
   appear in all capitals, as shown here.

3.  Carrying VTN Information in MPLS Packet

   This document defines a new VTN extension header which is used to
   carry the VTN-ID and other VTN related information.  In an MPLS
   packet, The VTN extension header follows the MPLS label stack, and
   precedes the header and payloads in the upper layer.  The format of
   VTN extension header is shown as below:

        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
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |Nibble | Length|    Flags      |         Reserved              |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       ~                             Options                           ~
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
           Figure 1. The format of MPLS VTN Extension Header



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   Where:

   *  Nibble: The first 4-bit field is set to the binary value 0010.
      This is to ensure that the VTN extension header will not be
      interpreted as an IP header or the ACH of pseudowire packet.

   *  Length: Indicate the length of the VTN extension header in 32-bit
      words.

   *  Flags: 8-bit Flags field.  All the flags are reversed for future
      use.  This field SHOULD be set to zero on transmission and MUST be
      ignored on receipt.

   *  Reserved: 16-bit field reserved for future use.

   A new VTN-ID Option is defined in this document, other option types
   may be defined in future documents.  The format of the VTN-ID Option
   is shown as below:

            Option   Option                Option
             Type   Data Len                Data
          +--------+--------+--------+--------+--------+--------+
          |BBCTTTTT|00000100|              VTN-ID               |
          +--------+--------+--------+--------+--------+--------+
                     Figure 2. The format of VTN-ID Option

   Option Type: 8-bit identifier of the type of option.  The type of
   VTN-ID option is to be assigned by IANA.  The highest-order bits of
   the type field are defined as below:

   *  BB 00 The highest-order 2 bits are set to 00 to indicate that a
      node which does not recognize this type will skip over it and
      continue processing the header.

   *  C 1 The third highest-order bit are set to 1 to indicate this
      option may change en route.

   Opt Data Len: 8-bit unsigned integer indicates the length of the
   option Data field of this option, in octets.  The value of Opt Data
   Len of the VTN-ID option SHOULD be set to 4.

   Option Data: 4-octet identifier which uniquely identifies a VTN
   within a network domain.








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   A new MPLS special-purpose label or extended special-purpose label is
   defined as the VTN Extension Header Indicator (VEHI), its value is to
   be assigned by IANA.  The VEHI label is used to indicate the
   existence of the VTN Extension Header after the MPLS label stack in
   the packet.  The position of the VEHI label in the MPLS label stack
   is not limited.

   The benefit of introducing the MPLS VTN Extension Header to carry the
   VTN-ID and the related information is that it provides the
   flexibility to encode information which cannot be accomodated in an
   MPLS label (20-bit), and the length of the header can be variable.

4.  Procedures


4.1.  VTN Header Insertion

   When the ingress node of an LSP receives a packet, according to
   traffic classification or mapping policy, the packet is steered into
   one of the VTNs in the network, then a VTN header SHOULD be inserted
   into the packet, and the VTN-ID which the packet is mapped to SHOULD
   be carried in the VTN header.  The ingress node SHOULD also
   encapsulates the packet with an MPLS label stack which are used to
   determine the path traversed by the LSP.  The VHI label SHOULD be
   inserted in the label stack to identify the existence of the VTH
   header.

4.2.  VTN based Packet Forwarding

   On receipt of a MPLS packet which carries the VHL and the VTN header,
   network nodes which support the mechanism defined in this document
   SHOULD scan the label stack to figure out the existence of the VHL.
   If there is a VHL in the label stack, then the network node SHOULD
   parse the VTN header and use the VTN-ID to identify the VTN the
   packet belongs to, and use the local resources allocated to the VTN
   to process and forward the packet.  The forwarding behavior is based
   on both the top MPLS label and the VTN-ID.  The top MPLS label is
   used for the lookup of the next-hop, and the VTN-ID can be used to
   determine the set of network resources allocated by the network nodes
   for processing and sending the packet to the next-hop.

   There can be different approaches used for allocating network
   resources on each network node to the VTNs.  For example, on one
   interface, a subset of forwarding plane resource (e.g. bandwidth and
   the associated buffer/queuing/scheduling resources) allocated to a
   particular VTN can be considered as a virtual layer-2 sub-interface
   with dedicated bandwidth and the associated resources.  In packet
   forwarding, the top MPLS label of the received packet is used to



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   identify the next-hop and the outgoing Layer 3 interface, and the
   VTN-ID is used to further identify the virtual sub-interface which is
   associated with the VTN on the outgoing interface.

   Network nodes which do not support the mechanism in this document
   SHOULD ignore the VHL and the VTN header, and forward the packet only
   based on the top MPLS label.

   The egress node of the MPLS LSP SHOULD pop the VEHL together with
   other LSP labels, and decapsulate the VTN header.

5.  Capability Advertisement and Negotiation

   Before inserting the VTN header into an MPLS packet, the ingress node
   MAY need to know whether the nodes along the LSP can process the VTN
   header properly according to the mechanisms defined in this document.
   This can be achieved by introducing the capability advertisement and
   negotiation mechanism for the VTN header.  The ingress node also need
   to know whether the egress node of the LSP can remove the VTN header
   properly before parsing the upper layer and send the packet to the
   next hop.  The capability advertisement and negotiation mechanism
   will be described in a future version of this document.

6.  IANA Considerations

   IANA is requested to assign a new special-purpose label from the
   "Special-Purpose MPLS Label Values" or "Extended Special-Purpose MPLS
   Label Values" registry.

      Value        Description                  Reference
      -------------------------------------------------------
      TBD     VTN Extension Header Indicator    this document

   IANA is requested to assign a new option type of the MPLS VTN
   extension header:

      Value        Description            Reference
      -------------------------------------------------
      TBD            VTN-ID             this document

7.  Security Considerations

   TBD

8.  Contributors

      Zhibo Hu
      Email: huzhibo@huawei.com



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9.  Acknowledgements

   TBD.

10.  References

10.1.  Normative References

   [I-D.ietf-teas-enhanced-vpn]
              Dong, J., Bryant, S., Li, Z., Miyasaka, T., and Y. Lee, "A
              Framework for Enhanced Virtual Private Network (VPN+)
              Services", Work in Progress, Internet-Draft, draft-ietf-
              teas-enhanced-vpn-09, 25 October 2021,
              <https://www.ietf.org/archive/id/draft-ietf-teas-enhanced-
              vpn-09.txt>.

   [I-D.ietf-teas-ietf-network-slices]
              Farrel, A., Drake, J., Rokui, R., Homma, S., Makhijani,
              K., Contreras, L. M., and J. Tantsura, "Framework for IETF
              Network Slices", Work in Progress, Internet-Draft, draft-
              ietf-teas-ietf-network-slices-08, 6 March 2022,
              <https://www.ietf.org/archive/id/draft-ietf-teas-ietf-
              network-slices-08.txt>.

   [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>.

   [RFC3031]  Rosen, E., Viswanathan, A., and R. Callon, "Multiprotocol
              Label Switching Architecture", RFC 3031,
              DOI 10.17487/RFC3031, January 2001,
              <https://www.rfc-editor.org/info/rfc3031>.

   [RFC7274]  Kompella, K., Andersson, L., and A. Farrel, "Allocating
              and Retiring Special-Purpose MPLS Labels", RFC 7274,
              DOI 10.17487/RFC7274, June 2014,
              <https://www.rfc-editor.org/info/rfc7274>.

   [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>.

10.2.  Informative References

   [I-D.dong-teas-nrp-scalability]
              Dong, J., Li, Z., Gong, L., Yang, G., Guichard, J. N.,
              Mishra, G., Qin, F., Saad, T., and V. P. Beeram,



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              "Scalability Considerations for Network Resource
              Partition", Work in Progress, Internet-Draft, draft-dong-
              teas-nrp-scalability-01, 7 February 2022,
              <https://www.ietf.org/archive/id/draft-dong-teas-nrp-
              scalability-01.txt>.

   [RFC3209]  Awduche, D., Berger, L., Gan, D., Li, T., Srinivasan, V.,
              and G. Swallow, "RSVP-TE: Extensions to RSVP for LSP
              Tunnels", RFC 3209, DOI 10.17487/RFC3209, December 2001,
              <https://www.rfc-editor.org/info/rfc3209>.

   [RFC5036]  Andersson, L., Ed., Minei, I., Ed., and B. Thomas, Ed.,
              "LDP Specification", RFC 5036, DOI 10.17487/RFC5036,
              October 2007, <https://www.rfc-editor.org/info/rfc5036>.

   [RFC8402]  Filsfils, C., Ed., Previdi, S., Ed., Ginsberg, L.,
              Decraene, B., Litkowski, S., and R. Shakir, "Segment
              Routing Architecture", RFC 8402, DOI 10.17487/RFC8402,
              July 2018, <https://www.rfc-editor.org/info/rfc8402>.

   [RFC8660]  Bashandy, A., Ed., Filsfils, C., Ed., Previdi, S.,
              Decraene, B., Litkowski, S., and R. Shakir, "Segment
              Routing with the MPLS Data Plane", RFC 8660,
              DOI 10.17487/RFC8660, December 2019,
              <https://www.rfc-editor.org/info/rfc8660>.

   [TS23501]  "3GPP TS23.501", 2016,
              <https://portal.3gpp.org/desktopmodules/Specifications/
              SpecificationDetails.aspx?specificationId=3144>.

Authors' Addresses

   Zhenbin Li
   Huawei Technologies
   Huawei Campus, No. 156 Beiqing Road
   Beijing
   100095
   China
   Email: lizhenbin@huawei.com


   Jie Dong
   Huawei Technologies
   Huawei Campus, No. 156 Beiqing Road
   Beijing
   100095
   China
   Email: jie.dong@huawei.com



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