Network Working Group                                            J. Dong
Internet-Draft                                                     Z. Li
Intended status: Standards Track                     Huawei Technologies
Expires: 6 September 2022                                         C. Xie
                                                                   C. Ma
                                                           China Telecom
                                                               G. Mishra
                                                            Verizon Inc.
                                                            5 March 2022


 Carrying Virtual Transport Network (VTN) Identifier in IPv6 Extension
                                 Header
                 draft-ietf-6man-enhanced-vpn-vtn-id-00

Abstract

   Virtual Private Networks (VPNs) provide different customers with
   logically separated connectivity over a common network
   infrastructure.  With the introduction and evolvement of 5G and other
   network scenarios, some existing or new customers may require
   connectivity services with advanced characteristics comparing to
   traditional VPNs.  Such kind of network service is called enhanced
   VPNs (VPN+).

   A Virtual Transport Network (VTN) is a virtual underlay network which
   consists of a set of dedicated or shared network resources allocated
   from the physical underlay network, and is associated with a
   customized logical network topology.  VPN+ services can be delivered
   by mapping one or a group of overlay VPNs to the appropriate VTNs as
   the virtual underlay.  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 performed on each node the
   packet traverses.

   This document proposes a new Hop-by-Hop option of IPv6 extension
   header to carry the VTN Resource ID, which is used to identify the
   set of network resources allocated to a VTN for packet processing.
   The procedure for processing the VTN option is also specified.

Status of This Memo

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







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Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   3
     1.1.  Requirements Language . . . . . . . . . . . . . . . . . .   4
   2.  New IPv6 Extension Header Option for VTN  . . . . . . . . . .   4
   3.  Procedures  . . . . . . . . . . . . . . . . . . . . . . . . .   5
     3.1.  VTN Option Insertion  . . . . . . . . . . . . . . . . . .   5
     3.2.  VTN based Packet Forwarding . . . . . . . . . . . . . . .   5
   4.  Operational Considerations  . . . . . . . . . . . . . . . . .   6
   5.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   6
   6.  Security Considerations . . . . . . . . . . . . . . . . . . .   6
   7.  Contributors  . . . . . . . . . . . . . . . . . . . . . . . .   7
   8.  Acknowledgements  . . . . . . . . . . . . . . . . . . . . . .   7
   9.  References  . . . . . . . . . . . . . . . . . . . . . . . . .   7
     9.1.  Normative References  . . . . . . . . . . . . . . . . . .   7
     9.2.  Informative References  . . . . . . . . . . . . . . . . .   7
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .   8








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1.  Introduction

   Virtual Private Networks (VPNs) provide different customers with
   logically isolated connectivity over a common network infrastructure.
   With the introduction and evolvement of 5G and other network
   scenarios, some existing or new customers may require connectivity
   services with advanced characteristics comparing to traditional VPNs,
   such as resource isolation from other services or guaranteed
   performance.  Such kind of network service is called enhanced VPN
   (VPN+).  VPN+ service requires the coordination and integration
   between the overlay VPNs and the network characteristics of the
   underlay.

   [I-D.ietf-teas-enhanced-vpn] describes a framework and the candidate
   component technologies for providing VPN+ services.  It also
   introduces the concept of Virtual Transport Network (VTN).  A Virtual
   Transport Network (VTN) is a virtual underlay network which consists
   of a set of dedicated or shared network resources allocated from the
   physical underlay network, and is associated with a customized
   logical network topology.  VPN+ services can be delivered by mapping
   one or a group of overlay VPNs to the appropriate VTNs as the
   underlay, so as to provide the network characteristics required by
   the customers.  In packet forwarding, traffic of different VPN+
   services need to be processed separately based on the network
   resources and the logical topology associated with the corresponding
   VTN.

   [I-D.dong-teas-enhanced-vpn-vtn-scalability] describes the
   scalability considerations and the possible optimizations for
   providing a relatively large number of VTNs for VPN+ services.  One
   approach to improve the data plane scalability of VTN is to introduce
   a dedicated VTN Resource Identifier (VTN Resource ID) in the data
   packet to identify the set of network resources allocated to a VTN,
   so that VTN-specific packet processing can be performed using that
   set of resources, which avoids the possible resource competition with
   services in other VTNs.  This is called Resource Independent (RI)
   VTN.  A VTN Resource ID represents a subset of the resources (e.g.
   bandwidth, buffer and queuing resources) allocated on a given set of
   links and nodes which constitute a logical network topology.  The
   logical topology associated with a VTN could be defined using
   mechanisms such as Multi-Topology [RFC4915], [RFC5120] or Flex-Algo
   [I-D.ietf-lsr-flex-algo], etc.

   This document proposes a mechanism to carry the VTN resource ID in a
   new Hop-by-Hop option of IPv6 extension header [RFC8200] of IPv6
   packet, so that on each network node along the packet forwarding
   path, the VTN option in the packet is parsed, and the obtained VTN
   Resource ID is used to instruct the network node to use the set of



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   network resources allocated to the corresponding VTN to process and
   forward the packet.  The procedure for processing the VTN Resource ID
   is also specified.  This provides a scalable solution to support a
   relatively large number of VTNs in an IPv6 network.

1.1.  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.

2.  New IPv6 Extension Header Option for VTN

   A new Hop-by-Hop option type "VTN" is defined to carry the VTN
   related Identifier in an IPv6 packet.  Its format is shown as below:

                     Option   Option       Option
                      Type   Data Len       Data
                   +--------+--------+-------------------------+
                   |BBCTTTTT|00000100| 4-octet VTN Resource ID |
                   +--------+--------+-------------------------+
                       Figure 1. The format of VTN Option

   Option Type: 8-bit identifier of the type of option.  The type of VTN
   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 0 The third highest-order bit are set to 0 to indicate this
      option does not 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 VTN option SHOULD be set to 4.

   VTN Resource ID: 4-octet identifier which uniquely identifies the set
   of network resources allocated to a VTN.

   Editor's note: The length of the VTN Resource ID is defined as
   4-octet in correspondence to the 4-octet Single Network Slice
   Selection Assistance Information (S-NSSAI) defined in 3GPP [TS23501].





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

3.  Procedures

   As the VTN option needs to be processed by each node along the path
   for VTN-specific forwarding, it SHOULD be carried in IPv6 Hop-by-Hop
   options header when the Hop-by-Hop options header can be either
   processed or ignored in forwarding plane by all the nodes along the
   path.

3.1.  VTN Option Insertion

   When an ingress node of an IPv6 domain receives a packet, according
   to the traffic classification or mapping policy, the packet is
   steered into one of the VTNs in the network, then the packet SHOULD
   be encapsulated in an outer IPv6 header, and the Resource ID of the
   VTN which the packet is mapped to SHOULD be carried in the VTN option
   of the Hop-by-Hop options header associated with the outer IPv6
   header.

3.2.  VTN based Packet Forwarding

   On receipt of a packet with the VTN option, each network node which
   can process the VTN option in fast path SHOULD use the VTN Resource
   ID to determine the set of local network resources allocated to the
   VTN for packet processing.  The packet forwarding behavior is based
   on both the destination IP address and the VTN Resource ID.  More
   specifically, the destination IP address is used to determine the
   next-hop and the outgoing interface, and VTN Resource ID is used to
   determine the set of network resources on the outgoing interface
   which are reserved to the VTN for processing and sending the packet.
   The Traffic Class field of the outer IPv6 header MAY be used to
   provide Diffserv treatment for packets which belong to the same VTN.
   The egress node of the IPv6 domain SHOULD decapsulate the outer IPv6
   header which includes the VTN option.

   In the forwarding plane, there can be different approaches of
   partitioning the local network resources and allocating them to
   different VTNs.  For example, on one physical interface, a subset of
   the forwarding plane resources (e.g. the bandwidth and the associated
   buffer and queuing resources) can be allocated to a particular VTN
   and represented as a virtual sub-interface with reserved bandwidth
   resource.  In packet forwarding, the IPv6 destination address of the
   received packet is used to identify the next-hop and the outgoing



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   layer-3 interface, and the VTN Resource 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 processing of Hop-by-Hop
   options header SHOULD ignore the Hop-by-Hop options header and
   forward the packet only based on the destination IP address.  Network
   nodes which support Hop-by-Hop Options header, but do not support the
   VTN option SHOULD ignore the VTN option and continue to forward the
   packet based on the destination IP address and MAY also based on the
   rest of the Hop-by-Hop Options.

4.  Operational Considerations

   As described in [RFC8200], network nodes may be configured to ignore
   the Hop-by-Hop Options header, and in some implementations a packet
   containing a Hop-by-Hop Options header may be dropped or assigned to
   a slow processing path.  The proposed modification to the processing
   of IPv6 Hop-by-Hop options header is specified in
   [I-D.ietf-6man-hbh-processing].  Operator needs to make sure that all
   the network nodes involved in a VTN can either process Hop-by-Hop
   Options header in the fast path, or ignore the Hop-by-Hop Option
   header.  Since a VTN is associated with a logical network topology,
   it is practical to ensure that all the network nodes involved in that
   logical topology support the processing of the HBH options header and
   the VTN option.  In other word, packets steered into a VTN MUST NOT
   be dropped due to the existence of the Hop-by-Hop Options header.  It
   is RECOMMENDED to configure all the network nodes involved in a VTN
   to process the Hop-by-Hop Options header and the VTN option if there
   is a nob for this.

5.  IANA Considerations

   This document requests IANA to assign a new option type from
   "Destination Options and Hop-by-Hop Options" registry.

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

6.  Security Considerations

   The security considerations with IPv6 Hop-by-Hop options header are
   described in [RFC8200], [RFC7045] and [I-D.ietf-6man-hbh-processing].
   This document introduces a new IPv6 Hop-by-Hop option which is either
   processed in the fast path or ignored by network nodes, thus it does
   not introduce additional security issues.




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7.  Contributors

      Zhibo Hu
      Email: huzhibo@huawei.com

      Lei Bao
      Email: baolei7@huawei.com

8.  Acknowledgements

   The authors would like to thank Juhua Xu, James Guichard, Joel
   Halpern and Tom Petch for their review and valuable comments.

9.  References

9.1.  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>.

   [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>.

   [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>.

   [RFC8200]  Deering, S. and R. Hinden, "Internet Protocol, Version 6
              (IPv6) Specification", STD 86, RFC 8200,
              DOI 10.17487/RFC8200, July 2017,
              <https://www.rfc-editor.org/info/rfc8200>.

9.2.  Informative References

   [I-D.dong-teas-enhanced-vpn-vtn-scalability]
              Dong, J., Li, Z., Gong, L., Yang, G., Guichard, J. N.,
              Mishra, G., and F. Qin, "Scalability Considerations for
              Enhanced VPN (VPN+)", Work in Progress, Internet-Draft,
              draft-dong-teas-enhanced-vpn-vtn-scalability-04, 25
              October 2021, <https://www.ietf.org/archive/id/draft-dong-
              teas-enhanced-vpn-vtn-scalability-04.txt>.



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   [I-D.ietf-6man-hbh-processing]
              Hinden, R. M. and G. Fairhurst, "IPv6 Hop-by-Hop Options
              Processing Procedures", Work in Progress, Internet-Draft,
              draft-ietf-6man-hbh-processing-00, 29 January 2022,
              <https://www.ietf.org/archive/id/draft-ietf-6man-hbh-
              processing-00.txt>.

   [I-D.ietf-lsr-flex-algo]
              Psenak, P., Hegde, S., Filsfils, C., Talaulikar, K., and
              A. Gulko, "IGP Flexible Algorithm", Work in Progress,
              Internet-Draft, draft-ietf-lsr-flex-algo-18, 25 October
              2021, <https://www.ietf.org/archive/id/draft-ietf-lsr-
              flex-algo-18.txt>.

   [RFC4915]  Psenak, P., Mirtorabi, S., Roy, A., Nguyen, L., and P.
              Pillay-Esnault, "Multi-Topology (MT) Routing in OSPF",
              RFC 4915, DOI 10.17487/RFC4915, June 2007,
              <https://www.rfc-editor.org/info/rfc4915>.

   [RFC5120]  Przygienda, T., Shen, N., and N. Sheth, "M-ISIS: Multi
              Topology (MT) Routing in Intermediate System to
              Intermediate Systems (IS-ISs)", RFC 5120,
              DOI 10.17487/RFC5120, February 2008,
              <https://www.rfc-editor.org/info/rfc5120>.

   [RFC7045]  Carpenter, B. and S. Jiang, "Transmission and Processing
              of IPv6 Extension Headers", RFC 7045,
              DOI 10.17487/RFC7045, December 2013,
              <https://www.rfc-editor.org/info/rfc7045>.

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

Authors' Addresses

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


   Zhenbin Li
   Huawei Technologies
   Huawei Campus, No. 156 Beiqing Road



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   Beijing
   100095
   China
   Email: lizhenbin@huawei.com


   Chongfeng Xie
   China Telecom
   China Telecom Beijing Information Science & Technology, Beiqijia
   Beijing
   102209
   China
   Email: xiechf@chinatelecom.cn


   Chenhao Ma
   China Telecom
   China Telecom Beijing Information Science & Technology, Beiqijia
   Beijing
   102209
   China
   Email: machh@chinatelecom.cn


   Gyan Mishra
   Verizon Inc.
   Email: gyan.s.mishra@verizon.com
























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