In the new 5G era, the existing networks face such new requirements as bandwidth upgrade, service expansion, convenience and flexibility. To ensure the rapid and sustainable development of telecommunications services, operators urgently need to make breakthroughs in network transport, service models, service provisioning, and O&M. With the increasingly urgent requirements for cloud-network synergy and the launch of the "three gigabit" services, China Telecom has been focusing on how to guarantee a consistent user experience across fixed and mobile networks and reduce network construction costs while meeting the requirements for high bandwidth, low latency, and differentiated transport services.
New Requirements: Exploring Future Network Development
With the deepening of enterprise informatization and the continuous development of mobile Internet and cloud services, various new services and applications have emerged. There is a continuous increase of fixed broadband traffic and a rapid growth of mobile services. The robust growth of 4K/8K video, cloud AR/VR and the distinctive rise of online education put large bandwidth requirements on mobile and fixed transport networks. Autonomous driving and telemedicine require low latency. The rapid development of 2B services require end-to-end on-demand network resource allocation. Intelligentization, openness, and service-based capabilities have become core demands of a new network. The future network needs a re-architecture centered on cloud-network synergy.
In March 2020, China Telecom started the research on the new metropolitan area network (MAN) solution, with an aim to unify the IP MAN and STN network architecture to build fixed and mobile convergence (FMC) networks, improve network efficiency, and reduce network construction costs. In April 2020, China Telecom deployed pilots in five provinces, including the MANs of Chengdu, Shenzhen, Wuxi, Shanghai, Huzhou, and Hangzhou, to verify the feasibility of the new MAN solution.
New Architecture: FMC for Flexible and Efficient Transport
Adopting a new spine-leaf architecture for networking, China Telecom's new MAN is constructed with point of delivery (POD) as a unit, and supports FMC unified transport. The network is modular and able to expand horizontally like "lego blocks". The service control layer has centralized control and provides resource pooling, breaking the isolation between the hardware resources and improving the efficiency of broadband user access and resource utilization. The network cooperates with multiple levels of cloud resource pools with the NEs deployed close to the user to improve response speed and reliability.
The architecture of the new MAN pilot is shown in Fig. 1, which consists of the access layer (STN-A, OLT), the aggregation layer (A-Leaf) and the metro backbone layer (Spine, B-Leaf, etc.).
Relying on the 163 and CN2 backbone networks, the new MAN architecture can adapt to traffic localization requirements, support multi-service integrated transport, meet the requirements of large bandwidth, low latency, end-to-end slicing, security and reliability, and base station and home broadband transport. It can also accommodate cloud-based distributed deployments of 5G core networks, MEC and service platforms while meeting transport requirements of government & enterprise private lines/cloud-based private lines. By reconstructing the architecture and transport modes, China Telecom has created a new MAN with flexible service deployment, efficient traffic forwarding, and on-demand NE scheduling.
New Operation: New-Generation Cloud-Network Operation System
China Telecom's new MAN employs the new-generation cloud-network operation support system, which could realize the orchestration and coordination of the new MAN. Using this support system, the network can achieve the goals of cloud-network integration, the integrated transport and automatic provisioning of 5G, major customers, home broadband and other services, flexible adjustment as well as online control.
As the brain of the entire new MAN, the operation support system is able to control the MAN fabric NEs such as Spine, Leaf, B and vBRAS-U in a centralized way. With it, the network can perform the configuration tasks for necessary services, intelligent O&M and automatically deliver the configurations.
The intelligent management & control system is the key to ensuring efficient, stable, and reliable network operations. Take the intelligent configuration detection as an example. The configuration detection efficiency can be improved by 90% with the risk identification rate reaching 85%, and the manpower required is shortened from 90 persons to 7 persons per day. This greatly improves the operation efficiency and reduces the network faults. ZTE has deployed its controllers in pilot sites in Chengdu and Shanghai, which work with the O&M support system of China Telecom for intelligent and automatic management of networks and equipment.
New Technology: Simplified Deployment and On-Demand Provisioning of Services
China Telecom's new MAN adopts the new EVPN over SRv6 technology to realize unified fixed and mobile service transport, cloud-network synergy, and convenient end-to-end service provisioning. The FlexE slicing technology is used to build end-to-end rigid pipes to provide differentiated transport services.
The EVPN technology introduces a new network model for Ethernet service delivery. With EVPN, operators can simplify their networks, improve efficiency, and meet evolving requirements for high bandwidth, sophisticated QoS and SLA guarantees. It has become the best model for operators to select for their networks.
SRv6 is a basic technology for future networks and is developing at a fast space. ZTE SRv6 supports 10 layers of labels and can provide powerful planning capability for paths and services. With the support from the network and service orchestrator, SRv6 can implement the cloud-network path connection and service definition. It is the technology of choice for cloud-network synergy and end-to-end service definition, and provides a new means for fast VPN service deployment.
The FlexE technology can decouple service rates from physical channel rates. It is used to establish end-to-end FlexE tunnels to isolate multiple service flows. The intermediate nodes do not need to parse service packets, and the one-hop transmission improves service transmission efficiency and physical isolation.
ZTE's related IP products with a complete SRv6/EVPN/FlexE function set have been actively deployed and verified in the existing network. At the forefront of standardization and implementation, ZTE is pushing forward the development of new technologies and protocols in the IP field.
Planned and guided by experts from China Telecom Group and provincial branches, ZTE fully participated in the new MAN pilot project with its front-end marketing and back-end R&D teams. Capitalizing on its deep technological accumulation in the IP field, ZTE has carried out large-scale network deployment and cutover, demonstrating its powerful strength in end-to-end products and end-to-end deployment. The stable operation of ZTE ZXCTN 9000-EA series, ZXR10 M6000-S series and ZXR10 V6000 vBRAS series and the successful application of SRv6/EVPN/FlexE mark a solid step from theoretical research to large-scale deployment of the new MAN. This is an important innovative achievement of China Telecom in re-architecting the network, which paves the way for the large-scale deployment of the new MAN in 2021.
China Telecom is committed to the research and practice of future network transformation under cloud-network synergy. The new MAN embodies simplicity, agility, centralization, openness and security in terms of network design, equipment selection, and technology selection, and meets the requirements for massive connections and high experience from future individual users, governments and enterprises, vertical industries, and IoT services with a new architecture, new protocol, and new operation. ZTE has made sufficient preparations in terms of intelligent solutions, equipment capability provision, and personnel training & reserves. The company is willing to work closely with China Telecom to actively explore the innovation of 5G network architecture, promote the development of new cloud-network services, and build a new engine for cloud-network synergy.