Unveil the next generation of optical transport networks: software-defined OTN

The challenges faced by traditional optical transport networks

Rapid traffic growth, single carrier capacity approaching the limit

In recent years, with the development of the Internet, the number of Internet users, the types of applications, and the bandwidth requirements have all exploded. In China, for example, the annual growth rate of trunk network traffic in the next 4 to 5 years will be as high as 60-70%. The total bandwidth of the backbone transmission network will increase from 64Tb/s to around 150Tb/s, even above 200Tb/s. In the face of huge digital torrents, the demand for ultra-high-speed optical interfaces has sprung up, and the transmission rate of lines has gradually developed from 40G/100G and 400G/1T+. Multi-carrier technology is the trend after 100G, how to improve the spectrum utilization efficiency of multi-carrier technology, and how Improving the overall spectrum utilization efficiency of the network through flexible adjustment of resources has become the primary issue for the next step.

New applications emerge in an endless stream, how do dynamic business floods?

With the wide application of cloud computing and data centers, various new types of new services and applications have emerged. In addition to the huge digital flood, the transport network will face the dynamic and unpredictable nature of the flood. Traditional optical transport networks are based on fixed-rate OTN interfaces, fixed-spectrum spectral spacing, and layer-by-layer separation management, with features such as over provisioning and "staTIc connecTIvity" under such conditions. It seems inefficient, and it is necessary to establish a flexible and open new architecture to achieve "automatic deployment" and "instantaneous bandwidth adjustment."

Software-defined OTN architecture

The software-defined optical transport network is an optical transport architecture that dynamically adjusts the transmission resources by software through flexible and programmable configuration of hardware. Its core technologies include: flexible and variable optical and electrical functional modules, high-speed, low-power programmable optical systems, Openflow standard control interfaces and open application interfaces (APIs), and programmable transfer controllers (Programmable) Transport Controller) implements optical network programming and resource cloudization to provide efficient, flexible and open pipeline network services for different applications. The system architecture is shown in Figure 1.

Figure 1 Software-defined OTN system architecture

Figure 1 Software-defined OTN system architecture

The software-defined OTN has three characteristics of “elastic pipeline”, “instant bandwidth” and “programming optical network”, which can meet the requirements of rapid deployment of different services, bandwidth on demand, network easy to manage, etc., which can effectively reduce operators. TCO, improving profitability.

Software-defined OTN, four key technologies

The software-defined OTN includes four key technologies: Flex OTN, Flex Transceiver, Flex ROADM, and Programmable Transport Controller.

Flex OTN technology

The traditional OTN implements encapsulation and bearer for multiple services such as TDM/IP through GMP technology. However, as the service rate increases, the mapping, encapsulation, and framing processing based on the fixed-rate OTUk interface cannot meet the operators' requirements for ultra-wideband. Flexible configurable bandwidth requirements, and different OTUks require different hardware counterparts, and are not compatible with software-programmable Flex Transceiver units. Based on the original OTN, Flex OTN introduces flexible OTN processing and integrates perfectly with the programmable optical layer, which not only expands the flexibility of OTN, but also is compatible with the existing network, which satisfies the flexibility and efficiency of multi-service for the future. Hosting.

Flex Transceiver technology

Transceiver is a unit that converts electrical signals and optical signals. Traditional Transceivers require a different hardware structure, different application scenarios, different modulation patterns, line rate boards or optical modules, and Flex Transceiver uses a common hardware structure. Based on the industry-leading flex-ODSP technology, a single hardware system can meet a variety of application scenarios with a simple software configuration and a single mouse click. With the Flex OTN and Programmable Transport Controller technology, users can follow the actual situation. In the service situation, the optical layer bandwidth resources are reasonably optimized and allocated, so that the traffic is refined and the overall power consumption of the network is reduced. Similar to the push of tunable lasers to optical networks, Flex Transceiver is bound to bring greater change.

Flex ROADM technology

The OADM unit that can be configured by the ROADM is an important optical layer physical unit that is indispensable in the optical network, and can implement wavelength channel switching and uplink and downlink in the optical layer. With the advent of 400G/1T+, in order to further improve the utilization of spectrum resources, the original fixed channel spacing was broken, and Flex ROADM came into being. Flex ROADM can achieve very small bandwidth separation, enabling lossless switching between arbitrary optical channels of any bandwidth. Combined with Flex OTN and Flex TRX technology, further finer sub-wavelength scheduling can be achieved in the optical layer. The layer is directly bypassed, reducing the use of expensive upper-layer switching equipment, reducing the operator's TCO and overall network power consumption.

Programmable Transport Controller Technology

The Programmable Transport Controller is a new type of network control unit. Through the standardized Openflow control interface with the network device layer, it provides unified control across multiple device configurations, enabling dynamic end-to-end unified control of flexible pipes from dynamic cloud services to Flex OTN, Flex TRX, and Flex ROADM, facilitating fast and instant value-added services. Providing; through the open API with the application layer, the application can drive the network, quickly and instantly reconstruct the network hardware system, realize the programmable optical network, meet the user dynamic real-time and personalized service requirements; through the centralized control concept The service multi-layer traffic grooming is more intelligent and controllable, the network resource utilization is maximized, and the end-to-end quality of the service is effectively guaranteed, so that the user can get the most perfect experience. This software-defined management approach based on centralized management, standardized control, and open APIs transforms the transport network from dumb to intelligent, and the pipeline provides operators with "OaaS" value-added services as part of the service (OpTIcal as a Service) ).

Software-defined OTN value

Operation and maintenance "easy", operation "fine"

In the traditional network, there are many types of boards, which increase the cost of preparation and operation and maintenance costs, and increase the operators' Capex and Opex. The software-defined OTN Flex OTN, Flex TRX, and Flex ROADM all use a common hardware architecture to achieve single-board hardware normalization. At the same time, because the optical module can be software-programmed, custom rate, pattern, etc., to network operation and maintenance. Operation also brings many benefits. For example, in the beginning of the project, the number of spare parts can be reduced, the technical requirements of the opening engineer can be reduced, the speed of the opening can be accelerated, and the service can be quickly opened and deployed. In the maintenance optimization stage, the optical fiber and optical components are deteriorated to cause transmission performance. When falling, you can optimize system performance by changing the modulation pattern. The flexible and configurable board can also provide operators with a more flexible bandwidth sales model to further increase revenue.

Bandwidth resources are “zero waste” and bandwidth value is “zero residue”

The “elastic pipeline” of the software-defined OTN makes it possible to manage and use refined bandwidth resources, and realize “zero waste” of bandwidth resources. The network controller reconfigures the optical layer hardware device according to the upper layer service traffic through the standard control interface, and adjusts the pipeline size. On the one hand, it can save network bandwidth resources and improve bandwidth utilization. For example, the 100G/400G/1T hybrid transmission system For example, the software-defined OTN can increase the bandwidth utilization rate by 40.3%~67.14%; on the other hand, it can also reduce the overall power consumption of the device and bring a green optical network.

The "instant bandwidth" of the software-defined OTN not only brings a different user experience, but also realizes the "zero residue" of the bandwidth value. The traditional optical transport network, from the user to send a bandwidth request, to the final service opening, needs to go through multiple departments, multi-person processing, opening up to several months, and through unified end-to-end control, combined with flexible optical physical layer technology , reducing people's participation, business opening time can be reduced to hours, even minutes and seconds, bandwidth resources rolling, not only improve the revenue per bit, but also bring a good ecosystem between ICP, ISP.

The “programming optical network” provided by the software-defined OTN enables the optical network to provide different network resources for different applications, and provides value-added services for operators as part of the service. By providing an open API, the network capability is abstracted to the application layer, and the application layer service-driven network establishes a connection according to the individualized requirements, so that the customer can easily implement the self-service network customization based on the standardized interface, and provide the service of the vain management. A closer and more intensive partnership with customers and content providers to create innovative profit growth points.

Flow, distance adaptation

The software-defined OTN can flexibly select the appropriate modulation format and spectrum resources according to the length of the optical path and the number of spans passing through. The short path of the small span can select a high-order modulation format that satisfies the OSNR requirement, and the number of spans is large and the transmission distance is long. The optical path can adopt a low-order modulation format that occupies a large bandwidth but can work normally at a low OSNR, thereby more effectively utilizing line spectrum resources and improving spectral efficiency.

Software-defined OTN is the inevitable evolution

In the era of cloud network, the business is diversified. The traditional optical transport network can no longer meet new demands. Efficient, flexible and open has become the key to the evolution of optical networks. At the turning point of change, Huawei proposes software-defined OTN in flexible pipelines. On the basis of providing instant bandwidth management, centralized control of virtualized network resources, and open standardized application interfaces, providing efficient, flexible, and open management of new services, enabling optical networks to better serve the service and serve the user experience. Customers continue to reduce operating costs and develop new profit models to build a healthier and more harmonious industrial chain.

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