Abstract: PeOTN is a flexible end-to-end transmission technology with rich service scheduling capabilities, supporting different transmission paths, and suitable for different future service scenarios. It can effectively improve the flexibility and scalability of the network. In order to meet the needs of new service carrying, PeOTN technology can be introduced into the metropolitan area network.
1. Overview of PeOTN Technology
PeOTN (Packet enhanced Optical Transport Network) is a flexible end-to-end transmission technology that can provide end-to-end flexible scheduling and support the transmission of various types of services. In terms of network architecture, PeOTN adopts OTN (Optical Transport Network) technology. By introducing point-to-multipoint and multipoint-to-multipoint transmission technologies, it can achieve flexible networking and scheduling while also realizing unified management of services and network resources.
2. The development history of PeOTN technology and its importance in the new era
PeOTN technology was first introduced by Federal Communications of the United States in 2018 and was officially incorporated into the ITU-TG.709 protocol in 2019. In March 2020, the ITU-TG.709 protocol adopted a recommendation on PeOTN technology.
Based on this suggestion, China Telecom officially launched the PeOTN pilot project in August 2020 and has completed the first phase of the pilot project, mainly conducting business tests in two scenarios.
PeOTN technology is suitable for metropolitan area network scenarios with diverse services and widely distributed users, and can effectively meet the flexibility and scalability requirements of the new era transmission network. The new era metropolitan area transmission network faces the following challenges:
First, future business will show a trend of diversification.
Second, the business has put forward higher requirements on the flexibility and scalability of the metropolitan area network.
Third, competition among operators will become more intense.
Faced with the above challenges, traditional OTN technology can no longer fully meet business needs, and new technologies must be introduced to meet the needs of network development in the new era. PeOTN technology was born out of necessity and is gradually maturing. It will become the mainstream metropolitan area network technology in the future.
1). Characteristics of PeOTN technology
PeOTN is the evolution of traditional OTN technology. Compared with traditional OTN technology, PeOTN has significantly improved network architecture, service deployment and management capabilities. Specifically, PeOTN has the following characteristics:
i. Strong scalability
PeOTN technology supports the expansion of new protection mechanisms based on traditional OTN, such as automatic protection and automatic recovery, which can realize the smooth upgrade of existing network equipment.
ii. Support the deployment of various types of services
PeOTN can support the deployment of various types of services in the metropolitan area network, such as service access and aggregation, large-granularity transmission, video conferencing, etc. Through flexible service deployment solutions, various types of services can be provided to users in the network.
iii. Support end-to-end network management capabilities
PeOTN supports multiple protocol stacks and multi-level management domains, which can realize centralized management and control of the entire metropolitan area transport network and monitor and maintain each node in the network.
iv. Have rich network capabilities
PeOTN supports a variety of service types and can achieve flexible expansion, protection switching, network reconstruction and other functions by configuring different transmission distances and protection mechanisms. For example, PeOTN supports the bearing and configuration of large-granularity services (such as 20GE and above); supports a variety of protection mechanisms (such as automatic, manual and semi-automatic), which can achieve flexible deployment of different types of services; and also has powerful network capabilities to achieve end-to-end fault
Switching.
v. Intelligent operation and maintenance capabilities
PeOTN supports a unified network monitoring management platform (NMS) and a multi-domain unified management platform (MDMS), which can realize centralized management and maintenance of the entire metropolitan area transport network.
2). China Telecom’s PeOTN pilot test
To promote the application of PeOTN technology in China Telecom, China Telecom organized relevant technical teams to conduct technical research and laboratory testing, mainly carrying out business testing in two scenarios.
Both scenarios involve a large number of terminal accesses, and the types of terminals are rich. In the base station access scenario, PeOTN technology can provide end-to-end SDH/OTN services and optical fiber resources. At the same time, since PeOTN technology supports flexible scheduling, adjustment and management, it can effectively reduce network costs and energy consumption. At present, China Telecom has completed the first phase of the pilot work. According to the pilot test results, PeOTN technology has shown strong performance advantages in the metropolitan area network scenario: in the base station access scenario, the metropolitan area transmission network scenario and the core network scenario, PeOTN can provide end-to-end SDH/OTN services and optical fiber resources.
At present, China Telecom has completed the relevant deployment work of the second phase of the pilot: first, two sets of PeOTN equipment were deployed in the base station access scenario; second, one set of PeOTN equipment was deployed in the metropolitan area transmission network scenario.
Overall, China Telecom’s pilot test is going well.
3). The importance of PeOTN in the new era
First, PeOTN technology is an important supplement to SDN technology. In the era of network intelligence, SDN technology provides important technical support for network intelligence. From a business perspective, with the trend of business cloudification and network intelligence, SDN technology can help operators realize network intelligence, network slicing, and network convergence. From a commercial perspective, SDN technology can provide operators with a customizable, scalable, and programmable network resource pool, helping operators achieve efficient use of resources.
Secondly, PeOTN is an inevitable trend in the future development of OTN. From the perspective of trends, with the advent of the 5G era, multi-service integration has put forward higher requirements for network performance. Therefore, the future transmission network needs to move from a single domain to multiple domains to meet the needs of diversified services. From a technical perspective, PeOTN is a transmission network technology oriented to the needs of multi-service integration, which can support multiple service types and multiple transmission network forms.
Thirdly, PeOTN is an important tool to help operators realize the “one network” strategy. From the existing market perspective, many operators are actively promoting the implementation of the “one network” strategy.
3. Application Scenarios of PeOTN Technology
PeOTN technology is a flexible end-to-end transmission technology that maps service traffic to optical channels with the same port to achieve flexible division of the transmission plane, thereby effectively meeting the requirements of different service bearers. PeOTN can support accurate scheduling of different services and can be widely used in the following scenarios in metropolitan area networks:
1). Multi-service carrying
PeOTN technology supports flexible scheduling and multi-path transmission of various types of services. PeOTN nodes can be flexibly deployed in the metropolitan area network according to business needs, and different business flows in the metropolitan area network can be classified, identified and accurately controlled by introducing PeOTN technology. When the business traffic on a certain path is too large, PeOTN technology can divert the business traffic to other paths, thereby reducing the traffic pressure on the path.
In addition, PeOTN can also classify and identify service flows according to different service types (such as MPLS-VPN/OTN/PW/GE private line, etc.), and implement accurate scheduling of different service flows. When carrying service flows on multiple paths at the same time, PeOTN technology can classify and identify different service flows on the path, thereby providing differentiated transmission services according to different service types[6].
2). Smart Pipeline
Traditional SDH/MSTP/OTN and other intelligent pipes differentiate the service traffic in the network according to different QoS levels. The main functions include QoS guarantee, multi-service integration and on-demand scheduling. Intelligent pipe technology can accurately control different types of traffic based on service type and bandwidth requirements and provide differentiated QoS guarantee, optimize the use of network resources and improve network efficiency while ensuring service QoS. Intelligent pipes can be used as an extension of SDH/MSTP/OTN and other intelligent pipes in the metropolitan area network. The following functions can be achieved through PeOTN technology:
i. Multi-service integration
Different types of services require different bearer platforms, and different bearer platforms can be selected according to traffic and bandwidth requirements. PeOTN technology can support the integration of multiple services, such as MPLS dedicated lines, Ethernet dedicated lines, video conferencing dedicated lines, etc.
ii. Intelligent traffic control
Intelligent pipes can classify and manage services according to traffic characteristics, thereby achieving accurate and on-demand traffic allocation. PeOTN technology can not only achieve intelligent traffic control but also take into account bandwidth guarantee, thereby achieving differentiated QoS guarantee. PeOTN technology can support multi-path transmission and dynamic bandwidth adjustment, and can quickly recover when a fault occurs, thereby ensuring service transmission quality.
iii. Multipath transmission
PeOTN technology supports multi-path transmission. When a failure occurs in the metropolitan area network, multiple PeOTN nodes can be used for backup, thus effectively coping with network failures.
iv. On-demand scheduling
Smart pipes can flexibly schedule traffic and adjust paths according to business needs. On the one hand, they can allocate traffic between different services, and on the other hand, they can quickly restore services when network failures occur. Smart pipes based on PeOTN technology will help operators optimize the configuration and on-demand scheduling of network resources, thereby improving network efficiency and benefits. Smart pipes can also be combined with existing SDH/MSTP/OTN technologies to further improve the overall efficiency of network transmission and control.
3). Multipath transmission
Multipath transmission refers to the use of different protection measures on different paths of service flows to ensure service transmission security. It is an extension and expansion of traditional SDH/MSTP and other technologies.
Based on the multipath transmission capability of PeOTN technology, the metropolitan area network can provide a flexible multipath service carrying solution. In the metropolitan area OTN network, by providing multipath protection for service flows, network resource utilization and network reliability can be improved, and network interruption caused by single point failure can be avoided.
4). Metropolitan Area Network Backbone Aggregation Layer
In the metropolitan area network backbone aggregation layer, multi-path transmission can be achieved through PeOTN technology, which can effectively improve the utilization rate of metropolitan area network backbone network resources. For example, in the core/backbone network of operators with large network scale, the service flows on multiple physical channels of the backbone aggregation layer can be multi-pathed by adopting PeOTN technology.It converts service traffic into optical signals of different wavelengths on different paths, thus maximizing the utilization of network resources while meeting service quality requirements.
4. PeOTN Technology Deployment Solution
In order to meet the flexible scheduling requirements of various services, it is necessary to classify and manage the services in layers. The physical layer network is the core layer, carrying all fixed and mobile services, such as the convergence layer that carries fixed, mobile and virtual networks, and the access layer of the IP network.The aggregation layer mainly carries voice, video, and large-granular data, while the access layer mainly carries broadband services. PeOTN technology can simultaneously meet the carrying requirements of the three types of services.
First, there are large-granularity data services with complex and diverse service types and flexible and changeable bandwidth requirements. In order to meet different service types, the transmission network needs to be flexibly managed in layers. In the traditional transmission network architecture, the aggregation and access devices of the transmission network are two relatively independent parts. For large-granularity data traffic, it needs to be forwarded through traditional aggregation devices and core devices, and the forwarding path is not fixed; for data traffic such as voice and video, voice and video need to be processed in a hierarchical manner, so they need to be forwarded through aggregation devices. Due to the characteristics of this large-granularity data traffic, it will bring great pressure to the traditional transmission network. PeOTN technology merges multiple transmission network elements into a general channel (GeneralPort), and each channel can carry different types of services. For voice services, the channels can be merged into one port; for video services, the channels can be merged into one port; for virtual private line services with relatively large traffic, the channels can be merged into one port. Because PeOTN technology adopts a unified standard, the traffic between each channel can be automatically identified and matched, greatly reducing the network congestion rate.
Secondly, voice and video services have relatively high bandwidth requirements and are sensitive to latency. These two types of data traffic have different bandwidth requirements and latency requirements. For voice services, voice services are relatively more sensitive to latency; while video services are relatively less sensitive to latency. Therefore, it is necessary to divide ports into two types: voice and video. For voice services, ports can be divided according to specific voice types; for video services, ports can be divided according to specific video types.
Next is the large-granularity data traffic, which accounts for the largest proportion of elastic large-granularity data traffic. This part of data traffic is managed, controlled, and forwarded through various control planes. This part of data traffic has no special requirements for transmission bandwidth, latency, etc., but has relatively high requirements for latency. For example, for two types of data traffic, voice and video, it is necessary to merge these two types of ports; for two types of ports, video and voice, it is necessary to merge these two types of ports.
Finally, there are low-latency and high-bandwidth services, which account for the largest proportion of low-latency sensitive data traffic, such as voice and video. This part of data traffic is relatively less sensitive to latency; but because it has high latency requirements, it needs to be differentiated and managed; for video and voice ports, these two types of ports need to be managed separately; for low-latency and high-bandwidth services, these two types of ports need to be managed together; for video and voice ports, these two types of ports need to be managed separately.
According to the above analysis, PeOTN technology will be widely used in various metropolitan area networks:
(1) The core aggregation layer will use PeOTN technology for backbone aggregation;
(2) The metropolitan area network access layer will use PeOTN technology for aggregation;
(3) The metropolitan area network aggregation layer will use PeOTN technology for backbone aggregation;
(4) The metropolitan area transport network will use PeOTN technology to achieve efficient, flexible and dynamic intercommunication between network nodes at all levels within the metropolitan area;
(5) PeOTN technology can be applied to the bearer requirements of different business scenarios in the future.
When deploying PeOTN technology, two aspects need to be considered: service type and transport network architecture.
4. Conclusion
In short, the application of PeOTN technology in my country’s optical fiber communication network in the new era is of great significance. With the rapid development of technologies such as 5G, cloud computing, and big data, PeOTN technology will usher in a wider range of application scenarios. Network operators should fully recognize the advantages of PeOTN technology, combine their own network needs, and rationally plan and develop PeOTN technology to improve the transmission efficiency and service quality of optical fiber communication networks. In the future, we have reason to believe that PeOTN technology will inject new vitality into the development of my country’s optical fiber communication network and help my country’s information technology reach a new peak.
**More related topic: https://ieeexplore.ieee.org/document/9325290
