The explosive growth of Internet applications poses greater challenges to network operations of operators. The price scissors phenomenon of revenues reflects that operators are gradually pipelined. The increasing volume of services does not generate corresponding incomes for operators, which is mainly caused by the rapid growth of bandwidth demands, high costs of operation and maintenance (O&M), long deployment period of new services, and slow revenue rise. As the Software Defined Network (SDN) and Network Functions Virtualization (NFV) technologies gradually mature, the SDN-based architecture is recognized by more and more Chinese operators, who are active players in the SDN pilot. This injects strong impetus to the bearer network architecture innovation.
Several major problems in optical transport networks (OTNs) need to be tackled from the industry chain. With centralized network control and management, O&M efficiency and resource utilization can be improved, and invalid processing of the traffic can be reduced. In addition, with integrated and open resources, innovative services can be deployed rapidly to bring better user experience and more revenues. In general, an efficient, elastic, and open optical network will be expected with the network upgrade and reconstruction technologies.
China Telecom is one of the first operators that have introduced SDN to their OTNs. In 2015, Beijing Research Institute of China Telecom and equipment manufacturers such as ZTE jointly conducted the second round of interworking tests for SDN-based OTNs. By the end of 2015, all tests as well as trials on live networks had been completed.
Two experts spoke about the test, technical, and deployment issues regarding the introduction of SDN to optical networks.
Q: At present, what has been done to introduce SDN to optical networks? What solutions are provided by the industry chain?
Jing Ruiquan: Currently, there are many problems and challenges in the construction and operation of OTNs, such as low O&M efficiency, long service deployment period, difficult OSS integration and cross-vendor interworking, low resource utilization, and slow service innovation. Therefore, China Telecom is actively promoting the application of SDN in OTNs. In 2015, China Telecom conducted SDN tests in two stages, that is, lab tests in Beijing laboratory in July and live network tests in two provinces in September and October. China Telecom developed system solutions, functional requirements, and interface protocol specifications for the tests, and independently developed a cross-vendor multi-domain controllers and service apps.
Wang Zhenyu: ZTE is committed to constructing elastic and efficient networks for global operators. We have introduced the all-in-one ElasticNet solution for the next-generation network architecture. As an important component of the overall SDN strategy, ZTE's SDN solution pushes the boundaries of intelligent management and control of optical networks, and effectively promotes integration and expansion of all network layers. The SDN system mainly consists of the application software, multi-domain controller, single-domain controller, and OTN equipment. ZTE provides the single-domain controller and OTN equipment, and actively cooperates with China Telecom to successfully complete SDN-based OTN tests.
Q: OTNs face many sticky problems. Can the introduction of SDN tackle problems faced by transport networks?
Wang Zhenyu: With the introduction of SDN to transport networks, transport capabilities of devices at the forwarding plane can be controlled in a finer manner. At the same time, the controller will have a global view due to the implementation of centralized control, E2E service configuration and deployment becomes easier and faster, and the entire network services can be optimized. Furthermore, the forwarding plane resources will be virtualized by the control plane to provide an elastic network. The control plane can also provide standard API interfaces and open network capabilities to promote the application innovation and facilitate the launch of new services for operators. The interworking and collaboration among multiple layers and domains can be implemented to support large-scale network construction.
Jing Ruiquan: The optical network is the basic carrier for cloud pipeline and high-bandwidth services. In the SDN control system, the next-generation network technology architecture, ultra-wideband bearer networks will be constructed for users and cloud services with the integration of IP and optical technologies. Resource utilization efficiency can be enhanced, O&M systems and planning can be simplified, and services can be deployed quickly through traffic tuning under collaboration among multiple networks, path optimization, and recovery protection.
Q: How are the research and commercial use of SDN-based OTNs going in the industry?
Jing Ruiquan: In September 2014, the OIF and ONF jointly organized the world's first interworking tests and demonstrations for SDN-based transport networks. In the laboratory of China Telecom, we use the self-developed multi-domain controller, together with single-domain controller and the domain OTN equipment manufactured by ZTE and other vendors to conduct tests. In 2015, we organized the second round of interworking tests for service scenarios, such as the intelligent transfer line (BoD) and virtual transport network service (VTNS), to move towards practical application.
Wang Zhenyu: From July to September in 2015, ZTE, together with China Telecom, conducted lab tests and live network tests in two provinces for typical BoD and VTS service scenarios. The tests met expected results. According to the innovation pattern, SDN will be tested and verified in several scenarios to reconstruct and verify existing software functions on optical networks in the SDN architecture.
Q: SDN will gradually be commercially used. What are the achievements for SDN pilot testing of China Telecom and the industry chain?
Jing Ruiquan: In the trial period, we tested the interworking between apps and multi-domain controllers and between multi-domain controllers and single-domain controllers provided by three vendors. What's more, we also verified capabilities of multi-domain controllers to obtain domain topology information and establish, query, and delete connections (including intra-domain and inter-domain connections).
Wang Zhenyu: ZTE, as a single-domain controller and device provider, completed ODUk and layer 2 Ethernet service establishment, deletion, and query, VTS service protection and restoration, BoD, and layer 2 Ethernet service performance information statistics in multi-vendor and multi-domain network scenarios. The tests have great reference values for future commercial SDN deployment.
Jing Ruiquan: Currently, we try to load government and enterprise private line services in the trial SDN-based OTN to provide innovative transport private line service capabilities, such as BoD. China Telecom will continue to cooperate with the device provider ZTE and SDN standardization organizations to test app services on live networks to collect and analyze user requirements, optimize product functions, and promote commercial deployment and application.
Q: Devices are bases for SDN-based optical network construction. Can devices on the live network be smoothly migrated to the SDN-based network? Can next-generation OTN devices meet requirements for future network convergence?
Jing Ruiquan: Smooth evolution is one of the challenges for evolving live networks to SDN-based optical networks. To protect existing investments, devices on the live network must be smoothly migrated to the SDN-based network. In this case, device providers must provide feasible solutions for southbound and northbound interfaces of SDN controllers and help operators complete SDN evolution.
Wang Zhenyu: ZTE has considered smooth network evolution in the SDN planning and R&D phases and is exploring an optimal path for SDN-based optical networks from the perspective of operators and device providers. ZTE provides an overall solution for devices, management, and O&M. The future will see the intelligent reconstruction of live OTNs. ZTE is planning functions of new-generation OTN products based on future SDN development requirements. The large-capacity product ZXONE 9700 provided by ZTE in the last year has 400 Gbit/s transport capabilities, programmable components, nodes, and networks, and ensures seamless convergence between PS networks and OTNs. All these functions of ZXONE 9700 lay a sound foundation for commercial SDN use.
Q: What is the procedure for SDN-based network deployment and commercial use?
Wang Zhenyu: The SDN-based network evolution of ZTE is based on the principle of stable, smooth, and customer value-centric. From 2013 to 2015, the SDN technology is developed and verified. ZTE optimized the SDN standard of the transport network with international standard organizations and operators and participated in the SDN-based transport network prototype verification and multi-vendor interworking organized by ONF and OIF. From 2016, the SDN-based transport networks will be commercially deployed and evolved. ZTE is deploying typical SDN functions to the live network to solve operators' problems.