RTGWG Working Group                                               S. Liu
Internet-Draft                                              China Mobile
Intended status: Standards Track                                H. Zheng
Expires: April 28, 2022                              Huawei Technologies
                                                        October 25, 2021

         Accessing Cloud via Optical Network Problem Statement


   This document describes the scenarios and requirements for the Cloud
   accessing through optical network, as a complementary functionality
   of the network and cloud coordination.  The problem from optical
   perspective is different with packet, and statement is made in this

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   the Trust Legal Provisions and are provided without warranty as
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Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
   1.1.  Requirements Language . . . . . . . . . . . . . . . . . . .   3
   2.  Scenarios . . . . . . . . . . . . . . . . . . . . . . . . . .   3
   2.1.  Multi-cloud accessing . . . . . . . . . . . . . . . . . . .   3
   2.2.  High-quality leased line  . . . . . . . . . . . . . . . . .   4
   2.3.  Cloud virtual reality . . . . . . . . . . . . . . . . . . .   5
   3.  Requirement and Problem statement . . . . . . . . . . . . . .   5
   3.1.  LxVPN of optical networks for multiple-to-multiple access .   5
   3.2.  Small Granularity Switching . . . . . . . . . . . . . . . .   6
   3.3.  High-performance and high-reliability . . . . . . . . . . .   6
   4.  Manageability Considerations  . . . . . . . . . . . . . . . .   6
   5.  Security Considerations . . . . . . . . . . . . . . . . . . .   7
   6.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   7
   7.  References  . . . . . . . . . . . . . . . . . . . . . . . . .   7
   7.1.  Normative References  . . . . . . . . . . . . . . . . . . .   7
   7.2.  Informational References  . . . . . . . . . . . . . . . . .   7
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .   7

1.  Introduction

   The cloud-related applications is becoming popular and wider
   deployed, in enterprises and vertical industries.  Companies with
   multi-campus are interconnected together with the remote cloud, for
   the purpose of storage and computation.  Such cloud services require
   high-level experiences including high availability, low latency, on-
   demand adjustment and so on.

   Optical is playing an important role in the transport network, with
   its own large bandwidth and low latency feature.  Based on the TDM
   switching technology, the data transportation in optical networks
   does not have any queuing problem to solve and can perfectly avoid
   congestion.  Such features can drastically improve the users
   experience on the service quality.

   Optical network is considered as the transportation solution for
   long-distance.  This feature is also suitable for the cloud
   interconnections, especially when there is demand for large

   [I-D.ietf-rtgwg-net2cloud-problem-statement] and
   [I-D.ietf-rtgwg-net2cloud-gap-analysis]gave a detailed description on
   the coordination requirements between the network and the cloud, and

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   it is expected the description in this document can be used as a
   complementary from the optical perspective.

1.1.  Requirements Language

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   "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.

2.  Scenarios

   With the prevalence of cloud services, enterprises services, home
   services such as AR/VR, accessing clouds with optical networks is
   increasingly attractive and becoming an option for the users.
   Following scenarios provide a few typical applications.

2.1.  Multi-cloud accessing

   Cloud services are usually supported by multiple interconnected data
   centers (DCs).  Besides the on-demand, scalable, high available and
   uses-based billing, mentioned in
   [I-D.ietf-rtgwg-net2cloud-problem-statement], there are also needs
   for Data Centre Interconnect (DCI) about high requirements on
   capacity, latency, and flexible scheduling.  This use case requires
   specific capabilities of advanced OTN (Optical Transport Network) for

      //------\\                                               /----\
    ||Enterprise|\\                                          |Vertical|
    ||   CPE    || \\        ------------          +-----+   /|Cloud |
      \\------//     \ +---*/            \*---+    |Cloud| //  \----/
                       |O-A|              |O-E|----+ GW  |/
                       +---+              +---+    +-----+
                      |      OTN Networks      |
      //-----\\       ++---+              +---+    +-----+     /-----\
    || Vertical||-----+ O-A|              |O-E|----+Cloud|---||Private||
     |   CPE   |      +----*\            /*---+    | GW  |    | Cloud |
      \\-----//              ------------          +-----+     \-----/

             Figure 1: Cloud Accessing through Optical Network

   A data center is a physical facility consisting of multiple bays of
   interconnected servers, that performs computing, storage, and
   communication needed for cloud services.  Infrastructure-as-a-service

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   may be deployed in both public and private clouds, where virtual
   servers and other virtual resources are made available to users on
   demand and by self-service.

   One typical scenario is the intra-city DCs, which communicate with
   each other via the intra-city DCI network to meet the high
   availability requirements.  The active-active and Virtual Machine
   (VM) migration services which require low latency are provided by the
   intra-city DCI network.  The intra-city DCI network supports the
   public and/or the private cloud services, such as video, games,
   desktop cloud, and cloud Internet cafe services.  To ensure low
   latency, intra-city DCI network is deployed in the same city or
   adjacent cities.  The distance is typically less than 100 km and more
   likely less than 50km.  One city may have several large DCs.

   DCs are ideally interconnected through Layer 2/3 switches or routers
   with full mesh connectivity.  However, to improve interaction
   efficiency as well as service experience, OTN is also evaluated as an
   option to be used for DC interconnection.

   There are three kinds of the connection relationship, point to point
   access, single to multiple point access, and multiple to multiple
   point access.  Different types of connections are referring different
   shapes, single point accessing single cloud, single point accessing
   multiple clouds and multiple points accessing multiple clouds.

2.2.  High-quality leased line

   The high quality private line provides high security and reliability
   and is suitable to ensure the end-to-end user experience for large
   enterprises such asfinancial, medical centers and education
   customers.  The main advantages and drivers of the high quality
   private line are as follows.

   o  High quality private lines provide large bandwidth, low latency,
      secure and reliable for any type of connection.

   o  Accelerate the deployment of cloud services.  The high-quality and
      high-security of the private line connecting to the cloud can
      enable enterprises to move more core assets to the cloud and use
      low-latency services on the cloud.  Cloud-based deployment helps
      enterprises reduce heavy asset allocation and improve energy
      saving, so that enterprises can focus on their major business.

   o  Reduce operator's CAPEX and OPEX.  The end-to-end service
      provisioning system enables quick provisioning of private line
      services and improves user experience.  Fault management can be
      done from the device level to reduce the complexity of location.

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   o  Enable operators to develop value-added services by providing
      enterprise users with latency maps, availability maps,
      comprehensive SLA reports, customized latency levels, and dynamic
      bandwidth adjustment packages.

2.3.  Cloud virtual reality

   Cloud Virtual Reality (VR) offloads computing and cloud rendering in
   VR services from local dedicated hardware to a shared cloud
   infrastructure.  Cloud rendered video and audio outputs are encoded,
   compressed, and transmitted to user terminals through fast and stable
   networks.  In contrast to current VR services, where good user
   experience primarily relies on the end user purchasing expensive
   high-end PCs for local rendering, cloud VR promotes the
   popularization of VR services by allowing users to enjoy various VR
   services where rendering is carried out in the cloud.

   Cloud VR service experience is impacted by several factors that
   influence the achieved sense of reality, interaction, and immersion,
   which are related to the network properties, e.g. bandwidth, latency
   and packet loss.  The network performance indicators, such as
   bandwidth, latency, and packet loss rate, need to meet the
   requirements to realize a pleasurable experience.

   The current network may be able to support early versions of cloud VR
   (e.g. 4K VR) with limited user experience, but will not meet the
   requirements for large scale deployment of cloud VR with enhanced
   experience (e.g.  Interactive VR applications, cloud games).  To
   support more applications and ensure a high-quality experience, much
   higher available and guaranteed bandwidth (e.g. larger than 1 Gbps),
   lower latency (e.g. less than 10 ms) and lower jitter (e.g. less than
   5 ms) are required.

3.  Requirement and Problem statement

3.1.  LxVPN of optical networks for multiple-to-multiple access

   To establish MP2MP connections, TDM transport technologies, like OTN,
   are adopting packet features.  Some OTN equipments have adopted
   packet processing functions, such as packet switching, MPLS VPN,
   etc., which could provide an underlay performance guaranteed TDM
   channel for cloud accessing, as an alternative of packet-based

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3.2.  Small Granularity Switching

   Accroding to the ITU-T G.709 recommendation, the OTN is providing TDM
   based connection with a granularity 1.25Gbps, which is more than the
   demand for normal user.  Most of the leased line is requesting a
   bandwidth less than 10Mbps, and the request from big enterprises are
   usually on the level of 100Mbps.  Therefore, most of the leased lines
   are with small granularity in the field.

   The SDH was a good complementary of OTN for small granularity
   solution, but SDH devices are gradually removed from the network due
   to End of Services.  As SDH networks gradually phase out, service
   providers start to think about how to utilize OTN networks to
   transmit small-granularity high-value SDH services.  The OSU (optical
   service unit) is proposed to solve the problem.

   At ITU-T, two work items, G.sub1G.sup and G.OSU, have been initiated
   aiming to enable OTN to support small-granularity services of 2M-1Gb/
   s.  For G.OSU, the general idea is to put small granularity services
   into OSU containers, and then put OSU containers into OPU payload
   areas.  OSU containers are flagged by Tributary Port Number (TPN)
   tags located at the overhead of the OSU containers.  At the
   intermediate nodes, OSUs can be switched to different directions
   based on the TPN tags in the overhead.  Given the development of OSU,
   the OTN is expected to be able to carry small granularity service and
   create end-to-end optical connections.

3.3.  High-performance and high-reliability

   To support the above-mentioned applications some of the network
   properties are critical to promise the Quality of Services (QoS).
   For instance, high bandwidth (e.g. larger than 1 Gbps), low latency
   (e.g. no more than 10 ms) and low jitter (e.g. no more than 5 ms),
   are required for Cloud VR.  In addition, small-granularity container
   is required to improve the efficiency of the networks.

   It is also critical to support highly reliable DCI for cloud
   services.  With advanced optical transport network protection and
   automatic recovery technologies, services can still run properly even
   fiber cuts occur in the DCI network.  Specific protection and
   restoration schemes are required, to provide high reliability for the

4.  Manageability Considerations


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5.  Security Considerations


6.  IANA Considerations

   This document requires no IANA actions.

7.  References

7.1.  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,

   [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>.

7.2.  Informational References

              Dunbar, L., Malis, A. G., and C. Jacquenet, "Networks
              Connecting to Hybrid Cloud DCs: Gap Analysis", draft-ietf-
              rtgwg-net2cloud-gap-analysis-07 (work in progress), July

              Dunbar, L., Consulting, M., Jacquenet, C., and M. Toy,
              "Dynamic Networks to Hybrid Cloud DCs Problem Statement",
              draft-ietf-rtgwg-net2cloud-problem-statement-11 (work in
              progress), July 2020.

Authors' Addresses

   Sheng Liu
   China Mobile

   Email: liushengwl@chinamobile.com

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   Haomian Zheng
   Huawei Technologies
   H1, Xiliu Beipo Village, Songshan Lake,
   Dongguan, Guangdong  523808

   Email: zhenghaomian@huawei.com

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