NeoTec                                                          Y. Zhang
Internet-Draft                                                    C. Xie
Intended status: Informational                             China Telecom
Expires: 23 April 2025                                   20 October 2024


           A Use Case of Network Operation for Telecom Cloud
                  draft-zx-neotec-net4cloud-usecase-00

Abstract

   This document discusses the network operation issues of telecom
   cloud.  It first introduces a typical use case of network for telecom
   cloud, then illustrates the requirements for network operation for
   telecom cloud from the perspective of TSP, and proposes a general
   network operation model for telecom cloud.  It also analyzes the gap
   based on the current technological status.

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   This Internet-Draft will expire on 23 April 2025.

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   provided without warranty as described in the Revised BSD License.



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Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
   2.  Terminology . . . . . . . . . . . . . . . . . . . . . . . . .   3
   3.  Use Case of Network for Telecom Cloud . . . . . . . . . . . .   3
   4.  Requirements  . . . . . . . . . . . . . . . . . . . . . . . .   7
   5.  Network Operation Model for Telecom Cloud . . . . . . . . . .   7
   6.  Gap analysis  . . . . . . . . . . . . . . . . . . . . . . . .   9
   7.  Security Considerations . . . . . . . . . . . . . . . . . . .  10
   8.  Normative References  . . . . . . . . . . . . . . . . . . . .  10
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  10

1.  Introduction

   Nowadays, the resources required for internet services and
   applications mainly exist in the form of cloud, which is distributed,
   decentralized and highly dynamic.  As a result, the network planning
   and operation methods need to be adjusted to meet the demands of
   cloud.

   Telecom cloud refers to a cloud computing system owned and operated
   by Telecom Service Provider (TSP).  In general, TSPs own and operate
   global wide area networks, 5G and cellular networks.  TSPs have also
   developed Telecom Cloud, which is a cloud environment optimized for
   service delivery through the integration of network and cloud
   infrastructure.

   To support cloud computing services, TSPs build overlay networks for
   corporate customer on the underlay network, and provides
   differentiated network services in terms of bandwidth, latency and
   security isolation to meet the flexibility needs of customers and
   applications.  Due to various reasons, overlay network and
   traditional underlay network have significant differences in planning
   and operation: overlay network can be quickly created and iteratively
   upgraded by TSPs, but it has poor awareness of the underlying
   network's operational status and potential failures.  Traditional
   underlay network focuses on traffic and connectivity, physical
   pipeline planning between cloud resource pools and network solutions
   for individual cloud network products, but not on application
   scenarios.  The network operation for telecom cloud is facing many
   challenges due to the lack of a customer or service-centric approach,
   as well as the inability to fully meet the demands of cloud services
   in terms of flexibility, openness, and response speed.

   For the illustration of network operation for telecom cloud, this
   document provides a typical use case of telecom cloud network.  It
   first introduces the architecture, then lists the requirements for
   operations of network for telecom cloud from the perspective of TSPs.



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   Additionally, it proposes a network operation model for telecom
   cloud, it also analyzes the current gaps in conjunction with the use
   case.

2.  Terminology

   The following terms are used in this document:

      CE: Customer Edge

      IOAM: Input Output Access Management

      MPLS: Multi-protocol Label Switching

      OTN: Optical Transport Network

      PE: Provider Edge

      POP: Point of Presence

      PW: Pseudo Wire

      SD-WAN: Software-Defined Wide Area Network

      SRv6: Segment Routing IPv6

      TSP: Telecom Service Provider

      VLAN: Virtual Local Area Network

      VPC: Virtual Private Cloud

3.  Use Case of Network for Telecom Cloud

   For the provisioning of cloud services to its customers, a TSP
   deploys its large-scale network in a distributed manner, with its
   backbone underlay network using MPLS or SRv6+EVPN methods, as shown
   in figure 1.  PE devices is located at the edge of the backbone
   network, responsible for connecting CE devices.  This Backbone
   Network connects cloud resource pools which distributes over a wide
   geographic area, so its users are capable of accessing local telecom
   cloud as well as remote telecom cloud.  On the access side, CE
   devices are located at the edge of customer sites, used to establish
   connections with PE devices.  When customers need to access the
   cloud, they can choose multiple methods, such as: IP RAN, PON, direct
   fiber drive, OTN, SD-WAN, 5G slice dedicated line.  Telecom cloud
   nodes can be deployed on the operator's Backbone Network or at the
   network edge.  Operators provide cloud services to enterprise



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   customers, including elastic computing, storage, networking, and
   security infrastructure resources, supporting enterprises to quickly
   build and deploy application systems and achieve rapid activation of
   internet services.

                               +------------+ +------------+
                               | Core Cloud | | Core Cloud |
                               +------------+ +------------+
                                     |              |
+------------+   +----+   +----+   +------------------+
| Edge Cloud |---| CE |---| PE |---|                  |
+------------+   +----+   +----+   |                  |
    +-----------------+   +----+   |                  |   +--------------+
    | Customer Site 1 |---| PE |---| Backbone Network |---| 3rd-Party    |
    +-----------------+   +----+   |                  |   | Public Cloud |
    +-----------------+   +----+   |                  |   +--------------+
    | Customer Site 2 |---| PE |---|                  |
    +-----------------+   +----+   +------------------+
            Figure 1. Diagram of typical network for Telecom Cloud

   In scenarios such as medical education and game streaming, one
   customer uploads data to the edge cloud through campus network and
   private cloud.  Important data, or data that has been preliminarily
   processed by the edge cloud, is then uploaded to the core cloud POP.
   At the same time, the core cloud also transmits data to the edge
   cloud.  Ultimately, customers can obtain the required data from
   either the edge cloud or the core cloud.

   Additionally, the operation of the cloud service requires underlay
   network support.  The cloud network service carrying methods for
   telecom cloud are mainly of two types:

   (1) Cloud Access Service

   Cloud access services allow customers to seamlessly connect their IT
   resources or data centers to telecom cloud resource pools via the
   telecom cloud management/control system.  These resource pool sites
   are typically deployed in proximity to customers to minimize data
   transmission latency and deliver a more localized service
   experience.This method not only provides network connection services
   but also integrates cloud computing resources.

   The current activation methods for Cloud Access Service include six
   types of network-side access: IP RAN, SD-WAN, PON, direct fiber
   connection, 5G slicing dedicated line, and OTN.  Each of these
   requires their respective network OSS systems to enable access
   services for cloud applications.




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   For example, customers directly access telecom cloud through the IP
   RAN network.  The IP RAN technology itself supports multiple service
   types, ensuring low latency and high reliability of data
   transmission, suitable for enterprise applications with higher
   network performance requirements.  It can dynamically adjust network
   resources according to enterprise customer needs.

   In this architecture, customers access the local operator's boundary
   equipment (PE) of the Backbone Network through the IP RAN network.
   The customer’s boundary equipment (CE) establishes a layer 2 channel
   with the ASBR/B-LEAF device through VLAN+PW.  The CE connects to the
   local IP RAN U equipment in a single or dual uplink mode,
   interconnected in a layer 2 VLAN manner.  A PW is established between
   the customer-accessed IP RAN U equipment and the ASBR/B-LEAF device
   to carry the customer’s layer 2 channel.  The ASBR device is
   interconnected with the local Backbone Network PE equipment within
   the local metropolitan area The CE acts as the three-layer gateway of
   its own internal network, being neighbors with the Backbone Network
   PE equipment at the three-layer level.  The above ASBR/B-LEAF devices
   reuse the IP RAN cloud dedicated line to provide customers with end-
   to-end complete services.

+----------+   +----+   +---+   +-------+   +------+   +----+   +----------+
| Customer |---| CE |---| U |---| IPRAN |---| ASBR |---| PE |---| Backbone |
| Site     |   +----+   +---+   +-------+   +------+   +----+   | Network  |
+----------+                                                    +----------+
             Figure 2. Diagram of Cloud Access Service network

   In this architecture, the cloud resource pool's cloud dedicated line
   switch acts as CE, connecting to the PE provided by the Backbone
   Network in the resource pool's city through a pre-configured high-
   bandwidth relay link.  Customers can conveniently access services
   through the nearest access point.  The connection between the cloud
   dedicated line switch and the Backbone Network PE adopts VLAN sub-
   interfaces to achieve flexible network configuration.  In the entire
   dedicated line service, the cloud dedicated line switch provides
   access functions, while the inter-cloud high-speed network handles
   networking and traffic scheduling tasks.  Different customers within
   the cloud resource pool achieve isolation through their own
   independent virtual routing and forwarding instances, ensuring
   security and privacy.

   (2) Inter-Cloud Connection Service

   To meet the needs of customers for networking between different cloud
   data centers, TSPs utilize cloud resource pools distributed in
   different regions to construct overlay network, such as SD-WAN or VPN
   on top of the underlay network, as shown in figure 3.  The overlay



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   network can quickly adjust configurations according to each
   customer's and each service's needs without being constrained by
   physical network elements in most cases.  The Overlay network
   directly serves customers on the cloud, providing customer-level/
   application-level virtual network connection, management, and
   monitoring services.

   The overlay network includes intra-cloud and inter-cloud.  The intra-
   cloud network mainly refers to VPC, a specific VPC acts as the core
   and links all intra-cloud network services.  VPC allows customers to
   build a secure, reliable, and configurable/manageable virtual network
   environment in the cloud while also supporting external network
   connections with various native cloud gateways and access to third-
   party public clouds.

   The underlay network provides high reliability and low latency
   network connection services for the overlay network on the cloud.  To
   support the overlay network, it is necessary to open basic network
   capabilities to the cloud management system through the underlay
   network's central controller and reserve resources such as VPN for
   the Overlay network.  However, it is not aware of customers and
   applications.

   The establishment of an overlay network include manual configuration
   and automated deployment.  Enterprise customers can manually
   configure parameters of network devices (such as routers, switches)
   according to their actual needs, including tunnel endpoints,
   encapsulation protocols, etc.  This method only works for small-scale
   network environments, but for large enterprises, manual configuration
   may be too cumbersome and prone to errors, necessitating automated
   deployment through network orchestrators.

                         +-------+            VxLAN                +-------+
  Overlay Network        |       |<------------------------------->|       |
                         | Edge  |        +-----------+            | Cloud |
           +-----+ IPSec | Cloud |  VxLAN | Municipal |   VxLAN    |       |
           |     |<----->|       |<------>| Cloud     |<---------->|       |
+------+   |     |       +-------+        +-----------+            +-------+
| USER |---| CPE |        | POP |            | POP |                | POP |
+------+   |     |   +-----+   +--------------+   +------------------+    |
           |     |---|     |---|    IP RAN    |---| Backbone Network |----+
           +-----+   | MAN |   | +----------+ |   |   +----------+   |
                     |     |   | | MPLS vpn | |   |   | MPLS vpn |   |
  Underlay Network   +-----+   | +----------+ |   |   +----------+   |
                               +--------------+   +------------------+
Figure 3. Diagram of constructing an Overlay network on Underlay network





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4.  Requirements

   From the perspective of TSPs, the network operation for telecom cloud
   should meet the following requirements:

   1) Agile provisioning: Capable of rapidly deploying and configuring
   cloud and network resources to promptly meet cloud service needs.

   2) Flexible adjustment of bandwidth and other resources: Dynamically
   adjust network bandwidth and other resources according to actual
   needs within minutes, ensuring efficient resource utilization.

   3) High stability and reliability: For new cloud services, such as AI
   computing, network failures could lead to training task interruptions
   or data loss.  The network needs to possess high stability and
   reliability to ensure continuous and complete data transmission.

   4) Network performance monitoring: The network operation system
   should have a unified interface and scheduling ability to ensure
   operable and manageable maintenance.  The system should be able to
   monitor the network's operating status in real-time, quickly detect
   and locate network problems of various computing nodes.  It should
   also support correlation analysis between application traffic and
   network status, providing customers with self-healing capabilities
   for overlay networks.  Through monitoring collaboration between cloud
   and network, it realizes predictive and planning functions of the
   network.

   5) Centralized control: Connect to DC, metropolitan area networks,
   backbone networks, and other network domains, apply SDN/NFV and other
   new technologies to achieve centralized control and dynamic
   management of network elements.

   6) Scenario visualization: Efficiently and promptly perceive network
   operational data, sense the real-time operating status of the
   network, and automatically discover changes in the network in a
   timely manner.  Realize panoramic visibility of end-to-end service
   paths and SLA visibility in the network.

5.  Network Operation Model for Telecom Cloud

   Telecom cloud must provide enterprises with flexible cloud computing
   resources, supporting the deployment and operation of various cloud
   applications and services, while also offering customers flexible
   network configuration and deployment services.  Therefore, its
   network operations need to be optimized.  This section introduces the
   network operation model for telecom cloud.  The top layer is the
   Telecom Cloud Service Management/Controller System, which includes



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   components such as orchestrator, controllers, fault operations,
   resource management, etc.  The Telecom Cloud Service Management/
   Controller System is responsible for comprehensively managing telecom
   cloud, building and operating overlay network.  At the same time,
   through interfaces with the Network Management/Controller System, it
   controls and mobilizes the capabilities of the underlying underlay
   network to meet the demands of cloud computing above.  This model
   also supports interoperability with third-party Public Cloud.

                                +----------------------------+
                                |         Application        |
                                +----------------------------+
                                       ^              ^
                                       |              |
                                       v              v
                      +---------------------+    +---------------------+
                      |    Telecom Cloud    |    |                     |
                      | +-----------------+ |    | Telecom Cloud       |
                      | |       VPC       | |<-->| Service Management/ |
                      | |-----------------| |    | Control System      |
                      | | Overlay Network | |    |                     |
                      | +-----------------+ |    |                     |
                      +---------------------+    +---------------------+
                                 ^                          ^
                                 |                          | Interface
                                 v                          v
  +--------------+     +------------------+     +---------------------+
  | 3rd-Party    |<--->| Underlay Network |<--->| Network Management/ |
  | Public Cloud |     |                  |     | Control System      |
  +--------------+     +------------------+     +---------------------+
              Figure 4. Network Operation Model for Telecom Cloud

   In this model, unified interfaces need to be established between the
   Telecom Cloud Service Management/Control System and the Network
   Control System to achieve seamless data exchange and command
   transmission.  This includes standardized API calls, data formats,
   and communication protocols.

   The main interfaces instructions sent by the Telecom Cloud Service
   Management/Control System to the Network Management/Control System
   include:

   *  Network establishment

   *  Cloud service operation data annoucement

   *  Network resource scaling on connection, bandwidth, latency, path,
      etc.



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   *  Retrieval of network performance data

   *  Retrieval of network resource usage data

   *  Network traffic scheduling

   *  Network termination

   Similarly, the Network Management/Control System can also report back
   to the Telecom Cloud Service Management/Control System.  Its
   interface includes:

   *  Proactive network fault reporting

   *  Proactive network performance reporting

   *  Proactive network resource usage reporting

   *  Proactive underlay network operation reporting

6.  Gap analysis

   Although telecom cloud providers have advantages in providing cloud-
   network integrated services, most networks, while extensive, are
   often rigid in operation, making them difficult to fully adapt to
   modern cloud service needs.

   As telecom cloud evolves towards multi-cloud and edge cloud models,
   new challenges in configuration, automation, and operation emerge.

   Moreover, interoperability becomes a key issue, as TSPs typically
   rely on equipment from multiple vendors, while public cloud providers
   can standardize on a single vendor ecosystem.  Telecom cloud services
   must seamlessly integrate various software and hardware systems,
   creating challenges and opportunities for collaboration, especially
   within IETF.  Addressing these challenges requires collaborative
   efforts to develop standardized solutions to ensure flexibility,
   scalability, and interoperability in the telecom cloud environment.

   1) Lack of definition for key interfaces and data models: Standardize
   the abstraction and interface definition of cloud and network
   resources for management across different vendors.  Achieve
   interoperability and seamless integration of cloud and network
   services.

   2) Lack of definition for cloud resource models: Abstract and define
   cloud resources, creating standardized resource models.  Establish
   unified interfaces and protocol standards to achieve flexible



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   combination and scheduling of virtual network resources, enhancing
   resource sharing and collaborative management between cloud and
   network.

   3) Lack of unified Input Output Access Management (IOAM): Extend IOAM
   to enhance real-time performance monitoring in cloud-integrated
   networks.  Develop standardized methods to manage cross-domain nested
   slices, enhancing visualization capabilities from the application
   layer to the network layer.

   4) Unified cloud-network orchestration mechanism: Develop a
   standardized orchestration layer connecting CRD (Custom Resource
   Definitions) in Kubernetes with NETCONF/YANG to improve coordination
   between computing resources and network resources.

7.  Security Considerations

   TBD.

8.  Normative References

   [RFC8466]  Wen, B., Fioccola, G., Ed., Xie, C., and L. Jalil, "A YANG
              Data Model for Layer 2 Virtual Private Network (L2VPN)
              Service Delivery", RFC 8466, DOI 10.17487/RFC8466, October
              2018, <https://www.rfc-editor.org/info/rfc8466>.

   [RFC8986]  Filsfils, C., Ed., Camarillo, P., Ed., Leddy, J., Voyer,
              D., Matsushima, S., and Z. Li, "Segment Routing over IPv6
              (SRv6) Network Programming", RFC 8986,
              DOI 10.17487/RFC8986, February 2021,
              <https://www.rfc-editor.org/info/rfc8986>.

Authors' Addresses

   Yue Zhang
   China Telecom
   Beiqijia Town, Changping District
   Beijing
   102209
   China
   Email: zhangy390@chinatelecom.cn










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   Chongfeng Xie
   China Telecom
   Beiqijia Town, Changping District
   Beijing
   102209
   China
   Email: xiechf@chinatelecom.cn












































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