5G, together with cloud computing and big data technologies, fully accelerates the digital transformation of the vertical industry. Vertical applications are diversified and have differentiated requirements for the network. A complete user service needs to traverse the entire network, connecting the network and cloud. ZTE's precision 5G transport network solution harnessing cloud and network synergy can meet the diversified requirements of various industries. 

New 5G Transport Network 
Service cloudification and technology innovation drive operators to shift from operating telecommunications services to providing integrated cloud services. Meanwhile, cloud services brought by cloud-network synergy promote network transformation.

Enterprise Cloud Migration 
With the rise of the digital economy, all vertical industries are carrying out a digital transformation, which is driving enterprise cloud migration. Operators are expanding their cloud service offerings year by year. Fast cloud access and flexible scheduling of cloud resources require an agile and intelligent network. That is to say, the network needs to be automated and programmable for fast service provisioning and differentiated service guarantees.

Cloudification of Core Network
5G brings in cloud-based architecture and technologies, and the cloudification of the core network provides new service capabilities such as network slicing and edge computing for consumers, application providers and vertical markets. The 5G transport network needs to allow for on-demand transmission of 5G services that cover a large area and require?multiple distributed edge data centers to the cloudified 5G core network. Therefore, the transport network needs to prioritize the cloud requirements, and work with the radio access network and core network to enable end-to-end network slices and provide low-latency network connections for edge computing.

Fixed Mobile Converged Transport
Traditional home broadband and mobile services will gradually migrate to the cloud, which makes the unified transport of home broadband and mobile services possible. Meanwhile, with the network device virtualization trend, the home broadband transport device BRAS deployed on the MAN first separates the control plane from the forwarding plane. The control plane implements cloudification and the forwarding plane provides centralized pooling. Therefore, it is possible to integrate the traditional fixed and mobile networks to carry home broadband, mobile, government & enterprise, and various cloud services through a single network.
ZTE proposes the precision 5G transport network solution to precisely match with various requirements of cloud and network development. 

Technologies for Precision 5G Transport Network
The precision 5G transport network solution is based on a series of new technologies and continuous improvement of network equipment software and hardware. The SRv6, FlexE and in-band OAM are cornerstones of the precision transport network.

SRv6 for Service Agility and Network Simplification
SRv6 simplifies protocol complexity and network operations, reduces resource occupation, enhances path adjustment and control capabilities, increases scalability, and finally facilitates network capability exposure. SRv6 also has the advantages of IPv6 such as massive address resources. The basic architecture and encapsulation format of SRv6 have been standardized, while SRv6 header compression, protocol extension and traffic engineering are being standardized.

FlexE for Deterministic Bandwidth and Latency
Flexible Ethernet (FlexE) is an interface technology that enables larger bandwidth and channelized sub-rate transport. On the one hand, FlexE can bind multiple Ethernet interfaces to obtain larger interface bandwidth. On the other hand, TDM-like rigid pipes are provided to ensure strict isolation between services and guaranteed bandwidth and latency. Therefore, the 5G transport network employs FlexE to implement hard pipe slicing and flexible bandwidth allocation. It can be integrated with SDN technology to achieve dynamic network adjustment.

In-Band OAM for Network and Service Status Perception
In-band OAM measures end-to-end and hop-by-hop packet loss and latency of real service flows. Compared with the traditional detection technology, in-band OAM allows operators to know real-time network status by performing real-time SLA monitoring, meeting daily OAM monitoring requirements. It also supports rapid fault localization and isolation, and with the coloring solution (RFC8321) avoids the extra overhead or just incurs a slight increase of overhead.

Precision 5G Transport Network Empowering Vertical Industries
The precision 5G transport network provides a variety of key capabilities, including precise bandwidth/latency guarantee, precise service delivery, precise path control, precise service detection and precise service security guarantee, to facilitate service innovation in various industrial scenarios and improve the precision service capabilities of the cloud and network.

Precision Pipe
Network slicing is a key feature of 5G end-to-end networks that enables independent end-to-end logical networks on the same physical network to fulfil diverse service requirements. Considering the large differences in service requirements and network costs, the transport network provides different slicing modes, including hard and soft slicing. 
Hard slicing is based on physically rigid pipes, such as FlexE and megabyte-level small-granularity hard pipe technologies. ZTE's full-series products with different port speeds (25/50/100/200/400GE) support FlexE, and exclusively allow 25GE FlexE. In addition, ZTE's in-house chips integrated with FlexE have low latency and low power consumption without increasing costs. The minimum 5 Gbps FlexE granularity is relatively large for some applications. Therefore, ZTE proposes the megabyte-level rigid pipe technology to guarantee the service bandwidth and latency at any granularity. A forwarding plane can use hard slicing to provide strict isolation for guaranteed service bandwidth and latency, that is, zero packet loss and low jitter in case of congestion. 
Soft slicing is based on statistical multiplexing, such as VPN, SRv6 tunnel and QoS scheduling. Soft slicing makes efficient use of the bandwidth to maximize network resource utilization. 
In practical applications, soft and hard slicing can be combined and deployed on demand to implement customized transport slices (Fig. 1) to meet personalized requirements of SLA-differentiated services, provide flexible, precise bandwidth and latency services and realize precise network operation, helping operators expand industry applications. 

Precision Management and Control
Network OAM in cloud and network synergy scenarios faces the challenges from diversified industrial application services and managing ultra-large-scale network connections. Therefore, the 5G transport network in support of cloud and network synergy must be automatic and intelligent. ZTE proposes the hierarchical management and control architecture and platform to implement precision 5G transport network management and control together with the agile forwarding plane.
Based on the architecture for unified orchestration and distributed management and control, the hierarchical management and control platform enables automation and intelligence by layers. The domain-based management and control layer supports batch configuration and automated configuration of unnecessary parameters, which changes the original point-by-point manual configuration mode to a highly automated one with minute-level service provisioning. This new mode provides multiple service templates, which can be selected flexibly based on the needs during service provisioning. Combined with the big data analysis and AI algorithms, it predicts network traffic and quality, and implements active OAM and intelligent management and control. The unified orchestration layer is integrated with an independent big data platform to accurately identify customers, and provide proactive analysis and guarantee for business logic implementation and service quality. Thus, "customer intelligence" and end-to-end service automation can be achieved.
SRv6 is introduced into the network forwarding plane to provide unified service transport. It achieves agile service provisioning with only the need for head-end configuration, and provides programmable service paths and application-level SLA. 
The hierarchical management and control plane in combination with the agile forwarding plane implements intelligent network OAM and flexible end-to-end service deployment and adjustment.

Precision Diagnosis
Traditional network diagnosis, which mainly relies on manual operation, has such problems as long processing time and low localization accuracy. ZTE proposes the intelligent diagnosis based on in-band OAM, Telemetry and AI algorithms to improve the network diagnosis efficiency, as shown in Fig. 2. In-band OAM is used to provide real-time visibility into network performance, real-time perception of network status, and rapid, precise fault localization. With its patented intelligent Telemetry data collection technology, ZTE also performs big data analysis to realize intelligent, dynamic traffic and path optimization.

Precision Security
Guaranteeing user data security is one of the goals of the transport network. ZTE 5G transport solution continuously improves the work flow in each phase of the network life cycle to guarantee service data security. For example, a hardware acceleration engine is added to a line card to perform direct protection switching in case of a hardware fault. Without the involvement of CPU, it can implement millisecond-level protection switching. The acceleration algorithm is also used to accelerate the convergence speed of routing protocols. Moreover, the equipment is upgraded without service interruption, avoiding upgrade restarts.

Summary
The future-oriented 5G transport network needs to accommodate the trend of service cloudification and cloud-network synergy and form a new unified transport plane for mobile, home broadband and government & enterprise services. Meanwhile, the precision 5G transport network will further help operators improve their cloud-network precision service capabilities so that 5G applications and innovative cloud and network applications can flourish in the new era.