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Problem Statement and Gap Analysis for Connecting to Cloud DCs via Optical Networks
draft-liu-ccamp-optical2cloud-problem-statement-07

Document Type Active Internet-Draft (individual)
Authors Sheng Liu , Haomian Zheng , Aihua Guo , Yang Zhao , Daniel King
Last updated 2024-10-21
Replaces draft-liu-rtgwg-optical2cloud-problem-statement
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draft-liu-ccamp-optical2cloud-problem-statement-07
CCAMP Working Group                                               S. Liu
Internet-Draft                                              China Mobile
Intended status: Standards Track                                H. Zheng
Expires: 24 April 2025                               Huawei Technologies
                                                                  A. Guo
                                                  Futurewei Technologies
                                                                 Y. Zhao
                                                            China Mobile
                                                                 D. King
                                                      Old Dog Consulting
                                                         21 October 2024

   Problem Statement and Gap Analysis for Connecting to Cloud DCs via
                            Optical Networks
           draft-liu-ccamp-optical2cloud-problem-statement-07

Abstract

   Optical networking technologies such as fine-grain OTN (fgOTN) enable
   premium cloud-based services, including optical leased line, cloud
   Virtual Reality (cloud-VR), and computing to be carried end-to-end
   optically between applications and cloud data centers (DCs), offering
   premium quality and deterministic performance.

   This document describes the problem statement and requirements for
   accessing cloud services through optical networks.  It also discusses
   technical gaps for IETF-developed management and control protocols to
   support service provisioning and management in such an all-optical
   network scenario.

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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   Internet-Drafts are draft documents valid for a maximum of six months
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   This Internet-Draft will expire on 24 April 2025.

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Copyright Notice

   Copyright (c) 2024 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
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   provided without warranty as described in the Revised BSD License.

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
   2.  Requirements and Gap Analysis . . . . . . . . . . . . . . . .   4
     2.1.  Multi-cloud Access  . . . . . . . . . . . . . . . . . . .   4
     2.2.  Service Awareness . . . . . . . . . . . . . . . . . . . .   5
   3.  Framework . . . . . . . . . . . . . . . . . . . . . . . . . .   6
     3.1.  Service Identification and Mapping  . . . . . . . . . . .   6
     3.2.  Reporting Service Identification  . . . . . . . . . . . .   7
     3.3.  Configuring Service Mapping . . . . . . . . . . . . . . .   7
   4.  Manageability Considerations  . . . . . . . . . . . . . . . .   8
   5.  Security Considerations . . . . . . . . . . . . . . . . . . .   8
   6.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   8
   7.  References  . . . . . . . . . . . . . . . . . . . . . . . . .   8
     7.1.  Normative References  . . . . . . . . . . . . . . . . . .   8
     7.2.  Informative References  . . . . . . . . . . . . . . . . .   9
   Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . .  10
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  10

1.  Introduction

   Cloud applications are becoming more popular and widely deployed in
   enterprises and vertical industries.  Organizations with multiple
   campuses are interconnected together with the remote cloud for
   storage and computing.  Such cloud services demand that the
   underlying network provides high quality of experience, such as high
   availability, low latency, on-demand bandwidth adjustments, and so
   on.

   Cloud services have been carried over IP/Ethernet-based aggregated
   networks for years.  MPLS-based VPNs with traffic engineering (TE)
   are usually used to achieve desired service quality.  Provisioning
   and management of MPLS VPNs is known to be complicated and typically
   involves manual TE configuration across the network.

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   To improve the performance and flexibility of aggregated networks,
   Optical Transport Network (OTN) technology is introduced to
   complement the IP/Ethernet-based aggregation networks to enable full-
   fiber connections.  This scenario is described in the Fifth
   Generation Fixed Network Architecture by the ETSI F5G ISG
   [ETSI.GR.F5G.001].  OTN can be used to provide high quality carrier
   services in addition to the traditional MPLS VPN services.  OTN
   provides Time Division Multiplexing (TDM) based connections with no
   queueing or scheduling needed, with an access bandwidth granularity
   of 1.25Gbps, i.e., ODU0 (Optical Data Unit 0) and above.  This
   bandwidth granularity is typically more than what a single
   application would demand, therefore, user traffic usually needs to be
   aggregated before being carried forward through the network.
   However, advanced OTN technologies developed in ITU-T work items have
   aimed to enhance OTN to support services of much finer granularity.
   These enhancements are reflected in the latest transmission standards
   of fine-grain OTN, or fgOTN, development by the ITU-T Q11/SG15
   [ITU-T.G.709.20-DRAFT]. fgOTN enables an even more suitable solution
   to bear cloud traffic with high quality and finer bandwidth
   granularity up to 10Mbps per time slot, which is very close to what
   an IP/Ethernet-based network could offer.

   Many cloud-based services that require high bandwdith, deterministic
   service quality, and flexible access could potentially benefit from
   the network scenario of using OTN-based aggregation networks to
   interconnect cloud data centers (DCs).  For example, intra-city Data
   Center Interconnects (DCIs), which communicate with each other to
   supports public and/or private cloud services, can use OTN for via
   intra-city DCI networks to ensure ultra-low latency and on-demand
   provisioning of large bandwidth connections for their Virtual Machine
   (VM) migration services.  Another example is the high quality private
   line, which can be provided over OTN dedicated connections with high
   security and reliability for large enterprises such as financial,
   medical centers, and education customers.  Yet another example is the
   Cloud Virtual Reality (VR) services, which typcially require high
   bandwidth (e.g., over 1Gbps for 4K or 8k VR) links with low latency
   (e.g., 10ms or less) and low jitter (e.g., 5ms or less) for rendering
   with satisfactory user experience.  These network properties required
   for cloud VR services can typically be offered by OTNs with higher
   quality comparing to IP/Ethernet based networks.

   [I-D.ietf-rtgwg-net2cloud-problem-statement] and
   [I-D.ietf-rtgwg-net2cloud-gap-analysis] present a detailed analysis
   of the coordination requirements between IP-based networks and cloud
   DCs.  This document complements that analysis by further examining
   the requirements and gaps from the control plane perspective when
   accessing cloud DCs through OTNs.  Data plane requirements are out of
   the scope of this document.

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2.  Requirements and Gap Analysis

2.1.  Multi-cloud Access

   Cloud services are typically deployed in geographically distributed
   locations for scalability and resilliency, and hosted by multiple
   DCs, each of which provides different cloud applications.  This
   requires a Point-to-Multi-Point (P2MP) or Multi-Point-to-Multi-Point
   (MP2MP) connectivity between service access points and the cloud DCs.
   The connectivities are traditionally provided over Layer 2/3
   connections.  To improve interaction efficiency as well as service
   experience, OTN (including fgOTN) is also considered as a viable
   option for DC interconnection.  This network scenario is illustrated
   in the example scenario Figure 1.

       __________                                             ________
      /          \                                           /        \
     | Enterprise |          ___________                    | Vertical |
     |    CPE     |\        /           \          +-----+ /|  Cloud   |
      \__________/  \ +---+/             \+---+    |Cloud|/  \________/
                     \|O-A*               *O-E|----+ GW  |
                      +---+               +---+    +-----+
        ________          |       OTN     |                    _______
       /        \     +---+               +---+    +-----+    /       \
      | Vertical |----+O-A*               *O-E|----+Cloud|---| Private |
      |   CPE    |    +---+\             /+---+    | GW  |   | Cloud   |
       \________/           \___________/          +-----+    \_______/

              Figure 1: Multi-cloud access through an OTN

   In this example, a customer application is connected to the cloud via
   one of the Customer Premises Equipment (CPE), and cloud services are
   hosted in multiple clouds that are attached to different cloud
   gateways.  Layer 2 or Layer 3 Virtual Private Networks (L2VPN or
   L3VPN) are used as overlay services on top of the OTN to support
   multi-cloud access.  Serving as an overlay, the OTNs should provide
   the capability to create different types of connections, including
   point-to-point (P2P), point-to-multipoint (P2MP) and multipoint-to-
   multipoint (MP2MP) connections to support diverse L2VPN or L3VPN
   services.

   In the data plane, OTN connections are P2P by nature.  To support
   P2MP and MP2MP services, multiple P2P OTN connections can be
   established between each source and destination pair.  The routing
   and signaling protocols for OTN need to coordinate these OTN
   connections to ensure they are routed with proper diverse paths to
   meet resilliency and path quality constraints.

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   [RFC4461] defines the requirements for establishing P2MP MPLS traffic
   engineering label switched paths (LSPs).  [RFC6388] describes
   extensions to the Label Distribution Protocol (LDP) for the setup of
   P2MP and MP2MP LSPs in MPLS Networks.  The generic rules introduced
   by those documents work also apply to OTNs, however, the protocol
   extensions are missing and are required for establishing P2MP and
   MP2MP connetctions with OTN resources, i.e., time slots.

2.2.  Service Awareness

   Cloud-oriented services are dynamic in nature with frequent changes
   in bandwidth and quality of service (QoS) requirements.  However, in
   typical OTN scenarios, OTN connections are preconfigured between
   provider edge (PE) nodes, and client traffic like IP or Ethernet is
   fixed-mapped onto the payload of OTN frames at the ingress PE node.
   This makes the OTN connections rather static and they cannot
   accommodate the dynamicity of the traffic unless they are permanently
   over-provisioned, resulting in slow and inefficient use of the OTN
   bandwidth resources.  To address this issue and to make the OTN more
   suitable for carrying cloud-oriented services, it needs to be able to
   understand the type of traffic and its QoS requirements, so that OTN
   connections can be dynamically built and selected with the best
   feasible paths.  The mapping of client services to OTN connections
   should also be dynamically configured or modified to better adapt to
   the traffic changes.

   New service-aware capabilties are needed for both the control plane
   and data plane to address this challenge for OTNs.  In the data
   plane, new hardware that can examine cloud traffic packet header
   fields (such as the IP header source and destination IP address and/
   or the type of service (TOS) field, virtual routing and forwarding
   (VRF) identifiers, layer 2 Media Access Control (MAC) address or
   virtual local area network (VLAN) identifiers) are introduced to make
   the PE node able to sense the type of traffic.  This work for the
   data plane is out of the scope of this document.

   Being service aware allows the OTN network to accurately identify the
   characteristics of carried client service flows and the real-time
   traffic of each flow, making it possible to achieve automated and
   real-time operations such as dynamic connection establishment and
   dynamic bandwidth adjustment according to preset policies.  Those
   capabilities help to optimize the resource utilization and
   significantly reduce the operational cost of the network.

   Upon examining the client traffic header fields and obtaining client
   information such as the cloud destination and QoS requirements, the
   OTN PE node needs to forward such information to the control entity
   of the OTN to make decisions on connection configurations, and map

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   the client packets of different destination/QoS to different ODU
   connections The client information could include, but is not limited
   to, the destination IP addresses, type of cloud service, and QoS
   information such as bandwidth, latency bounds, and resiliency
   factors.  The control entity may be an SDN controller or a control
   plane instace: in the former case communications are established
   between each of the PE nodes and the controller, and the controller
   serves as a central authority for OTN connection configurations;
   whereas in the latter case, all of the PE nodes need to disseimate
   client information to each other using control plane protocols or
   possibly through some intermediate reflectors.  It is desirable that
   the protocols used for both cases are consistent, and ideally, the
   same.  A candidate protocol is the PCE communication Protocol (PCEP)
   [RFC5440], but there are currently no extensions defined for
   describing such client traffic information.  Extensions to PCEP could
   be defined outside this document to support the use case.  It is also
   possible to use the BGP Link State (BGP-LS) protocol [RFC7752] to
   perform the distribution of client information.  However, an OTN PE
   node does not typically run BGP protocols due to that BGP lacks
   protocol extensions to support optical networks.  Therefore, PCEP
   seems to be a better protocol choice in this case.

3.  Framework

3.1.  Service Identification and Mapping

   The OTN PE node should support the learning and identification of the
   packet header carried by client services.  The identification content
   may include but not limited to the following content:

   *  Source and destination MAC addresses

   *  Source and destination IP addresses

   *  VRF identifier

   *  VLAN (S-VLAN and/or C-VLAN) identifier

   *  MPLS label

   The OTN PE node should support reporting the above identified client
   services to the management and control system, which can obtain the
   client-side addresses reported by each node in the entire network to
   build up a global topology.  Some of the learnt content, such as the
   VLAN identifier, are not required to be reported since VLAN is of
   only local significance.

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   The management and control system should be able to calculate the
   corresponding ODU connection route based on the source and
   destination addresses of the service, and create the mapping between
   service address and the ODU cnnection according to preset policies.
   The mapping table can be generated through management plane
   configuration or control plane protocol.

3.2.  Reporting Service Identification

   The control plane protocol extension should report to the controller
   service identification contents, which should include at least the
   following content:

   *  A private network or network slice identifier, which is a globally
      unique identifier to identify different tenants or applications
      supported by the private network

   *  OTN node identifier, which identify the OTN PE node that reported
      this packet

   *  The IP/MAC address of the client side learned by the OTN PE node

   When the PCEP protocol is used, this extension may be defined as a
   PCEP Report message.

3.3.  Configuring Service Mapping

   The control plane protocol extension may be defined to push the
   mapping table between service address to ODU connections from the
   controller to the OTN PE nodes.  The message should include at least
   the following content:

   *  A private network or network slice identifier, which is a globally
      unique identifier to identify different tenants or applications
      supported by the private network

   *  A mapping table of {service address, ODU connection identifier},
      with each entry of the table contains at least the information of
      {remote OTN node, remote service address}, where the concept of
      "remote" is based on the perspective of the OTN device that
      receives this packet

   When the PCEP protocol is used, this extension may be defined as a
   PCEP Update message.

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4.  Manageability Considerations

   TBD

5.  Security Considerations

   This document analyzes the requirements and gaps in connecting to
   cloud DCs over optical networks without defining new protocols or
   interfaces.  Therefore, this document introduces no new security
   considerations to the control or management plane of OTN.  Risks
   presented by existing OTN control plane are described in [RFC4203]
   and [RFC4328], and risks presented by existing northbound and
   southbound control interfaces in general are described in [RFC8453].
   Moreover, the data communication network (DCN) for OTN control plane
   protocols are encapsulated in fibers, which providers a much better
   security environment for running the protocols.

6.  IANA Considerations

   This document requires no IANA actions.

7.  References

7.1.  Normative References

   [ETSI.GR.F5G.001]
              European Telecommunications Standards Institute (ETSI),
              "Fifth Generation Fixed Network (F5G);F5G Generation
              Definition Release 1", ETSI GR F5G 001 , December 2020,
              <https://www.etsi.org/deliver/etsi_gr/
              F5G/001_099/001/01.01.01_60/gr_F5G001v010101p.pdf>.

   [ITU-T.G.709.20-DRAFT]
              ITU Telecommunication Standardization Sector (ITU-T),
              "Overview of fine grain OTN", ITU-T G.709.20 , December
              2023, <https://www.itu.int/itu-t/workprog/
              wp_item.aspx?isn=18873>.

   [RFC4203]  Kompella, K., Ed. and Y. Rekhter, Ed., "OSPF Extensions in
              Support of Generalized Multi-Protocol Label Switching
              (GMPLS)", RFC 4203, DOI 10.17487/RFC4203, October 2005,
              <https://www.rfc-editor.org/info/rfc4203>.

   [RFC4328]  Papadimitriou, D., Ed., "Generalized Multi-Protocol Label
              Switching (GMPLS) Signaling Extensions for G.709 Optical
              Transport Networks Control", RFC 4328,
              DOI 10.17487/RFC4328, January 2006,
              <https://www.rfc-editor.org/info/rfc4328>.

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   [RFC4461]  Yasukawa, S., Ed., "Signaling Requirements for Point-to-
              Multipoint Traffic-Engineered MPLS Label Switched Paths
              (LSPs)", RFC 4461, DOI 10.17487/RFC4461, April 2006,
              <https://www.rfc-editor.org/info/rfc4461>.

   [RFC5440]  Vasseur, JP., Ed. and JL. Le Roux, Ed., "Path Computation
              Element (PCE) Communication Protocol (PCEP)", RFC 5440,
              DOI 10.17487/RFC5440, March 2009,
              <https://www.rfc-editor.org/info/rfc5440>.

   [RFC6388]  Wijnands, IJ., Ed., Minei, I., Ed., Kompella, K., and B.
              Thomas, "Label Distribution Protocol Extensions for Point-
              to-Multipoint and Multipoint-to-Multipoint Label Switched
              Paths", RFC 6388, DOI 10.17487/RFC6388, November 2011,
              <https://www.rfc-editor.org/info/rfc6388>.

   [RFC7752]  Gredler, H., Ed., Medved, J., Previdi, S., Farrel, A., and
              S. Ray, "North-Bound Distribution of Link-State and
              Traffic Engineering (TE) Information Using BGP", RFC 7752,
              DOI 10.17487/RFC7752, March 2016,
              <https://www.rfc-editor.org/info/rfc7752>.

   [RFC8453]  Ceccarelli, D., Ed. and Y. Lee, Ed., "Framework for
              Abstraction and Control of TE Networks (ACTN)", RFC 8453,
              DOI 10.17487/RFC8453, August 2018,
              <https://www.rfc-editor.org/info/rfc8453>.

7.2.  Informative References

   [I-D.ietf-rtgwg-net2cloud-gap-analysis]
              Dunbar, L., Malis, A. G., and C. Jacquenet, "Networks
              Connecting to Hybrid Cloud DCs: Gap Analysis", Work in
              Progress, Internet-Draft, draft-ietf-rtgwg-net2cloud-gap-
              analysis-09, 15 June 2022,
              <https://datatracker.ietf.org/doc/html/draft-ietf-rtgwg-
              net2cloud-gap-analysis-09>.

   [I-D.ietf-rtgwg-net2cloud-problem-statement]
              Dunbar, L., Malis, A. G., Jacquenet, C., Toy, M., and K.
              Majumdar, "Dynamic Networks to Hybrid Cloud DCs: Problems
              and Mitigation Practices", Work in Progress, Internet-
              Draft, draft-ietf-rtgwg-net2cloud-problem-statement-41, 19
              August 2024, <https://datatracker.ietf.org/doc/html/draft-
              ietf-rtgwg-net2cloud-problem-statement-41>.

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Acknowledgments

   TBD

Authors' Addresses

   Sheng Liu
   China Mobile
   Email: liushengwl@chinamobile.com

   Haomian Zheng
   Huawei Technologies
   Email: zhenghaomian@huawei.com

   Aihua Guo
   Futurewei Technologies
   Email: aihuaguo.ietf@gmail.com

   Yang Zhao
   China Mobile
   Email: zhaoyangyjy@chinamobile.com

   Daniel King
   Old Dog Consulting
   Email: daniel@olddog.co.uk

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