SPN Private Line Technology and Its Applications

Private lines are an important service provided by telecommunications operators. However, traditional private lines face several challenges. These lines often come with a long provisioning period, failing to meet the enterprise’s agile provisioning and e-commerce requirements, lack transparency in network service quality, and are often outdated, leading to slow fault handling. Furthermore, the presence of various network standards results in high overall network construction and maintenance costs. Performance factors such as bandwidth and latency are in urgent need of improvement. The gradual phasing out of SDH equipment necessitates the replenishment of hard slicing network capabilities. New services such as 5G ToB private lines and enterprise-to-cloud have brought about new demands, including network security and programmability features.

In June 2022, China Mobile unveiled the slicing packet network (SPN) private line solution to address the aforementioned issues. This offering provides a cost-effective solution for industry sectors, featuring high isolation, flexible bandwidth, deterministic latency, network visibility, and intelligent operation & maintenance. Additionally, it supports multi-purpose use, reducing costs and improving efficiency, thus meeting the differentiated, higher requirements posed by digital transformation for private line services.

Overview of SPN Private Line Solution

China Mobile’s SPN private line solution comprises three products: the basic SPN private line, the premium SPN private line, and the customized SPN private network, as shown in Fig. 1.

The main features of the basic SPN private line include shared slices, ubiquitous access, and rapid provisioning. Services are carried on industry-specific private line slices, which are hard-isolated from the larger public network slices dedicated to ToC services. Soft isolation between private line services is implemented through a VPN network. Standard functions include multiple protection mechanisms and SLA visibility, while optional functions include provisioning progress visibility and topology visualization.

The premium SPN private line features fine granularity and high isolation. Services are carried through fine-granularity interfaces or channels, and isolation between services is achieved through fine-granularity hard slices. This meets the requirements for service isolation, deterministic latency, and security. Additionally,  functions such as rerouting and network manageability, controllability, and visibility can be provided.

The customized SPN private network offers integrated network services tailored to specific industries such as medical, education, and power. Different service levels can be provided within a private network slice as required, with the slice being  externally hard-isolated from other slices.

The SPN private line provides customers with an exclusive slice network, including soft slices, hard slices, and end-to-end channels. It fulfills high-bandwidth, high-burst service transport requirements while also addressing low-latency, low-jitter service demands. Additionally, it offers multiple layers of protection through mechanisms like rerouting and escape routing, along with various network self-service options.

SPN Private Line Technology

To establish a precise, integrated, intelligent, and low-carbon next-generation service transport network, SPN technology continually evolves to cater to various scenarios, including 5G transport, industry sectors, and government and enterprise networks. The rich customization capabilities of the SPN private line is built upon several key SPN technologies.

• Hard-Isolated Channel  

The SPN architecture innovatively introduces slicing Ethernet technology, which extends Ethernet slicing capabilities based on the native Ethernet kernel. It is fully compatible with current Ethernet networks while eliminating the need for packets to go through caching and table lookup at L2/L3. SPN also supports FlexE interfaces and slicing Ethernet cross-connect (SE-XC) channel technologies. This enables Ethernet physical layer networking, which provides deterministic low latency and hard pipe isolation, primarily used for basic slicing in 5G granularity.

Inheriting SPN’s efficient Ethernet kernel, SPN fine granularity unit (FGU) technology incorporates fine-granularity slicing into the SPN architecture through a hierarchical design, providing end-to-end fine-granularity hard pipes at the FGU sublayer. The FGU uses a TDM mechanism similar to SDH to achieve strict hard isolation between different services. By defining a fixed frame structure, this technology further divides the 5 Gbps time slot at the SPN channel layer, with a minimum granularity of 10 Mbps. SPN FGU technology constructs efficient, lossless, bandwidth-flexible, and reliable end-to-end channels and transport modes to meet differentiated transport requirements (e.g., low bandwidth, high isolation, and high security) in scenarios like 5G–for-industry-sector applications and private lines.

• Network Quality Perception

Leveraging inband operations, administration, and maintenance (OAM), SPN offers end-to-end inband and real-time monitoring capabilities, facilitating direct measurement of service packets. This enables real-time awareness of the SLA for each service and packet. With second-level telemetry data collection, unified control, computation, and visualization capabilities, it provides real-time visibility into network quality, active monitoring and rapid fault location.

ZTE’s inband OAM functionality supports a vast number of concurrent instances, self-learning of traffic control, and scenario-focused priority assurance, enhancing network quality perception capabilities of the SPN for carrying diverse services.

• Multiple Network Protection Mechanisms  

Within the SPN architecture, there exists both a centralized control plane for the management and control system and a distributed control plane for devices, providing multiple network protection mechanisms. The SPN provides basic linear protection modes, such as segment routing-transport profile (SR-TP) 1:1 protection, and also VPN fast reroute (FRR) node protection. These network protection mechanisms greatly improve the reliability and security of the SPN. Take the SR-TP tunnel as an example. If both working and protection paths in 1:1 protection fail, the SPN provides a rerouting protection solution. Furthermore, if a connection between the management and control system and a network device is interrupted, the distributed control plane for network devices may activate an escape route protection mechanism via segment routing-best effort (SR-BE) tunnel using the IGP protocol.

• Ubiquitous Coverage Capability

The SPN is a unified transport network that carries 5G backhaul, government and enterprise private lines, and enterprise-to-cloud services. With more than 400,000 SPN devices already deployed, its coverage area exceeds that of the optical transport network (OTN) and the IP metropolitan area network (MAN), but still smaller than that of the packet transport network (PTN). Give the importance of the last kilometer in rapid service provisioning, operators need a network capable of ubiquitous coverage. The deployment of indoor distribution devices and small cells brings the SPN network closer to the edge, enhancing its coverage capability to some extent.

Moreover, the deployment of SPN CPEs will greatly contribute to achieving ubiquitous coverage. SPN CPEs support FGU over a 10 GE interface, extending Nx10 Mbps hard pipes to office desks of the customer, facilitating end-to-end SPN slicing. With reduced capacity, they consume less power, enabling access for ToB services. Their 1U height and smaller size increase deployment flexibility. Additionally, SPN CPEs can network with MAN devices end-to-end through a network-to-network interface (NNI), reducing deployment difficulty. They also incorporate computing power for real-time data collection and analysis, enhancing data security by keeping data within the campus.

• Self-Service Capability

ZTE’s cloud native platform includes three engines (intent, control and perception) and two sub-platforms (big data and AI). The SPN management and control system is built on this platform, integrates network resources based on NE capabilities, and provides multiple self-service capabilities for customers.

—SLA visibility capability: Real-time service indicators of the network, such as traffic, latency, jitter, and packet loss, can be exposed to third parties. Government and enterprise customers can develop web and app portal interfaces to display SLA indicators in real time.

—Transparent provisioning capability: The service provisioning progress is visible so that customers can track the the provisioning status in detail.

—Private network connection topology: The SPN management and control system provides a slice view showing the connections between the headquarters and branches of the industrial customer, along with slice view-based management and maintenance functions.

—Online bandwidth adjustment: Based on dynamic bandwidth requirements, enterprise customers can submit bandwidth increase or decrease orders online, which are then delivered to the network through the service orchestration and control system. Network devices support lossless bandwidth adjustment.

SPN Private Line Technology Trials

The development of the SPN private line has gone through many stages. In 2020, function-level demonstrations were conducted, showcasing large-granularity slicing, agile network provisioning, and multiple network protection mechanisms. In 2021, trial commercial deployments started for functions such as small-granularity private lines and inband OAM with an aim to carry services for government and enterprise customers like electric power companies. In 2022, China Mobile launched a major SPN private line initiative, conducting live trials to validate the end-to-end transport of group customer services through SPN slices and to promote this technology in the market.  

The main items tested in the initiative were:

• Service performance: Evaluating end-to-end service performance in various scenarios, and comparing it with the current mode.
• Networking solution: Comparing the advantages and disadvantages of SPN networking solutions for various scenarios, along with their deployment, maintenance, management, and investment aspects. The networking solution for massive SPN deployment was also tested.
• Maintenance management: Examining key issues such as maintenance management modes of SPN services from different vendors.

This initiative comprised the inter-province and intra-province parts. ZTE participated in the Beijing-Guangdong inter-province same-vendor test, the Shanghai-Guangdong inter-province different-vendor test, as well as the intra-province same-vendor tests in Beijing and Guangdong. These tests fully validated various network protection switching functions including fine-granularity escape and interconnection protection, as well as functions like lossless bandwidth adjustment, service isolation, and network self-service. These tests also compared the SPN functions with those of PTN and OTN networks. Fig. 2 shows the inter-province private line test topology.

The test results demonstrated that the SPN could provide hard slicing with flexible granularity and facilitate lossless bandwidth adjustment. It could provide both hard and soft slicing simultaneously, along with multiple protection modes, such as rerouting and fine-granularity escape routes, to improve network security. The statistics of sent/received packets and latency obtained during inband OAM detection matched with those recorded by test meters, and network SLA indicators were effectively detected. The SPN’s network agility and self-service capabilities were also verified, confirming the completeness of its functions.

At the same time, China Mobile launched a live trial of the SPN CPE. The SPN CPEs were expected to facilitate access for various types of customer services and meet the flexible networking requirements across different vendors. By connecting with the NNI of the MAN SPN, the SPN CPEs could provide end-to-end fine-granularity hard slicing, hierarchical fault location, channel-associated inband OAM performance monitoring, L2/L3-to-edge multi-service access capability, and lossless bandwidth adjustment.

ZTE is committed to collaborating with the industry chain to utilize the technological advantages of the SPN to empower a multitude of industry sectors. Across networks in provinces including Shanxi, Shaanxi and Jilin, the SPN has already been extensively used to carry private line services for group customers. Industries like transportation and mining have begun significant commercial use of SPN technology. It is anticipated that in the near future, the SPN private line technology will see even wider adoption across many industries to create value for a vast array of users.