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Versions: 00 01                                                         
Network Working Group                                              Z. Li
Internet-Draft                                                   J. Dong
Intended status: Standards Track                     Huawei Technologies
Expires: August 26, 2021                               February 22, 2021


      Carrying Virtual Transport Network Identifier in MPLS Packet
                  draft-li-mpls-enhanced-vpn-vtn-id-00

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.

   This document proposes a mechanism to carry the VTN-ID and the
   associated information 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
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   material or to cite them other than as "work in progress."

   This Internet-Draft will expire on August 26, 2021.

Copyright Notice

   Copyright (c) 2021 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
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   described in the Simplified 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  . . . . . . . . . . . . . . . . . . . . . .   6
   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




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   based on the topology and the network resources associated with the
   corresponding VTN.

   For network scenraios where a large number of VTNs need to be created
   and maintained, [I-D.dong-teas-enhanced-vpn-vtn-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] based 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 header which is used to carry the
   VTN-ID and other VTN related information.  In an MPLS packet, The VTN
   header follows the MPLS label stack, and precedes the header and
   payloads in the upper layer.  The format of VTN header is shown as
   below:













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       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              |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                          VTN Identifier                       |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      ~                Service Differentiator  (Optional)             ~
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
                 Figure 1. The format of MPLS VTN Header

   Where:

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

   o  Length: Indicate the length of the MPLS VTN header in 32-bit
      words.

   o  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.

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

   o  VTN Identifier (VTN-ID): A 4-octet global significant identifier
      which uniquely identifies a VTN.

   o  Service Differentiator: A variable length field to identify a
      service instance which is carried by the VTN.  In the context of
      5G network slicing, this may be the Single Network Slice Selection
      Assistance Information (S-NSSAI) associated with the packet.

   Editor's note: The length of the VTN-ID is defined as 4-octet for the
   potential matching or mapping with the 4-octet S-NSSAI defined in
   3GPP [TS23501] for 5G network slicing.  One or multiple S-NSSAIs may
   be mapped to one VTN.

                          8-bit              24-bit
                     +------------+-------------------------+
                     |    SST     |   Slice Differentiator  |
                     +------------+-------------------------+
                         Figure 2. The format of S-NSSAI

   A new MPLS special-purpose label or extended special-purpose label
   [RFC7274] is defined as the VTN Header Indicator (VHI), its value is
   to be assigned by IANA.  The VHI label is used to indicate the



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   existence of the VTN Header after the MPLS label stack in the packet.
   The position of the VHI label in the MPLS label stack is not limited.

   The benefit of introducing the MPLS VTN header to carry the VTN-ID
   and the related information is that it provides the flexibility to
   encode information which cannot be accommodated 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 may also insert a
   Service Differentiator into the VTN header to further identify the
   service instance the packet belongs to.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.  The network
   node may further use the Service Differentiator information to
   provide some fine-grained differentiation and processing based on the
   local network resources allocated to the VTN.

   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 VHL 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

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

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

7.  Security Considerations

   TBD

8.  Contributors

      Zhibo Hu
      Email: huzhibo@huawei.com

9.  Acknowledgements

   TBD.






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10.  References

10.1.  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>.

   [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-enhanced-vpn-vtn-scalability]
              Dong, J., Li, Z., Qin, F., and G. Yang, "Scalability
              Considerations for Enhanced VPN (VPN+)", draft-dong-teas-
              enhanced-vpn-vtn-scalability-01 (work in progress),
              November 2020.

   [I-D.ietf-teas-enhanced-vpn]
              Dong, J., Bryant, S., Li, Z., Miyasaka, T., and Y. Lee, "A
              Framework for Enhanced Virtual Private Networks (VPN+)
              Service", draft-ietf-teas-enhanced-vpn-06 (work in
              progress), July 2020.

   [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>.






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   [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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