Recently, the M-OTN (Metro optimized OTN)/OSU (Optical Service Unit) multi service bearer technology led by China Telecom completed the industrys first cross vendor and cross city smooth upgrade test of existing network equipment in Anhui Telecom, and opened the first Ethernet dedicated line service based on OSU technology for friendly customers. The test was successful. The success of this experiment not only marks a significant milestone in the standardization, equipment development, and practical application of M-OTN/OSU technology, but also lays a solid foundation for the large-scale commercialization of M-OTN/OSU technology in the next stage.
Implementing the national strategy of "Network Power, Digital China", China Telecom actively promotes the high-speed ubiquitous "Cloud Network Integration 3.0", and jointly proposes the M-OTN technology system with OSU as the core in the industry, which makes up for the shortcomings of traditional OTN technology in carrying small particle services, such as low efficiency, delay pressure drop, and bandwidth loss adjustment difficulties. It provides a comprehensive service carrying solution for the next generation of urban transport networks that can not only guarantee high-quality service slicing requirements, but also meet the needs of low-cost, low latency, and low-power operation.

The current network experiment organized by Anhui Telecom focuses on verifying the large-scale deployment of equipment supporting M-OTN/OSU technology and the stability of long-term equipment operation, including key technologies such as M-OTN/OSU multi service hybrid bearer, cross vendor networking, bandwidth lossless adjustment, low latency, and smooth upgrading of OSU capabilities for current network equipment and network management systems.

The topology of the current network experiment is shown in Figure 1. The provincial backbone network spanning Huainan (City A) and Lu an (City B) uses the current network backbone OTN network. The core layer and aggregation layer M-OTN equipment of Huainan and Lu an metropolitan area networks are provided by ZTE Corporation, and the access layer M-OTN equipment is provided by Greenwell and ZTE respectively. Unlike the previous on-site network pilot using experimental equipment, this on-site network experiment uses commercial M-OTN devices to verify the introduction of new and upgraded OSU modes in two metropolitan area networks. The main achievements of this online experiment include:
Verified the ability to upgrade OSU without any business impact on network devices: by introducing OSU adapter cards or OSU business cards into existing OTN devices, it is possible to quickly and cost effectively obtain OSU business capabilities; Not only can it fully utilize the existing line cards and channel resources to protect existing network investments, but the upgrade process also has no impact on on on network services.
Verified the ability to uniformly carry multiple services: by introducing a hybrid line card that supports VC/ODU/OSU modes simultaneously, it can achieve unified carrying of multiple services such as E1, STM-N, EoS, EoO, EoOSU, etc.
Verified the stability and reliability of the device: Through friendly customer trial experience feedback and long-term error rate and packet loss rate hanging table testing, it has been confirmed that devices using OSU technology have the ability to operate stably for a long time, and the network operation is safe and reliable.
Verified the ability of fast lossless bandwidth adjustment: achieved second level lossless bandwidth adjustment in complex multi vendor environments, with a minimum adjustment granularity of 2.5Mbit/s for business bandwidth, thus solving the problem of long-term inability to scale commercial use of SDH LCAS and ODUflex G.HAO lossless bandwidth adjustment capabilities.
Verified low latency characteristics: After adopting OSU technology, the business mapping mechanism and processing hierarchy were optimized, reducing device processing latency. Compared with the EoSoO bearer method currently used in OTN networks, end-to-end circuit latency was reduced by 16% to 64%.
The current network test equipment follows the published "Technical Requirements for Metropolitan Optical Transport Network (M-OTN) Equipment" standard of China Telecom, and the successful testing of key functions such as OSU business, lossless bandwidth adjustment, and multi manufacturer interconnection fully demonstrates the maturity of China Telecoms leading M-OTN/OSU technology system. China Telecom is collaborating with companies such as China Unicom, China Academy of Information and Communications Technology, ZTE, Huawei, and FiberHome to enrich and improve standards, actively promoting the transformation of standards into industry and international standards.
At present, mainstream OTN equipment manufacturers such as Huawei, ZTE, FiberHome, Greenwell, and Rexroth are all able to provide commercial M-OTN/OSU devices, marking that M-OTN/OSU has moved from technical research and standard development to the commercialization stage of the entire industry chain. By introducing OSU capability through lossless upgrading of network devices, existing network investments can be maximally protected and the threshold for OSU introduction can be lowered. China Telecom will continue to innovate and lead the development of technology and standards in the M-OTN/OSU industry, collaborate with upstream and downstream parties in the industry chain to create a complete ecosystem, actively promote the scale deployment and application of M-OTN/OSU, enrich the network dedicated line service capabilities, enhance the business carrying capacity of the OTN network, and meet the usage requirements of different dedicated line users.