Unveiling the veil of the next generation optical transmission network: software-defined OTN

Challenges faced by traditional optical transport networks

Rapid traffic growth, single carrier capacity is approaching the limit

With the development of the Internet in recent years, the number of Internet users, types of applications, and bandwidth requirements have all shown explosive growth. Taking China as an example, the annual growth rate of mainline traffic in the next 4 to 5 years will be as high as 60 to 70%. The total bandwidth of the backbone transmission network will increase from 64Tb / s to around 150Tb / s or even above 200Tb / s. Facing the huge digital torrent, the demand for ultra-high-speed optical interfaces has emerged in large numbers. The line transmission rate has gradually evolved from 40G / 100G and 400G / 1T +. After over 100G, multi-carrier technology is the trend. The flexible adjustment of resources to improve the overall spectrum utilization efficiency of the network has become the primary issue for the next step of development.

New applications are emerging one after another, how to flood the dynamic business

With the widespread application of cloud computing and data centers, various new types of new services and applications have emerged. In addition to the huge digital torrent, the transmission network will also face the dynamics and unpredictability of the torrent. The traditional optical transmission network is based on a fixed-rate OTN interface, a fixed spectrum interval at the optical layer, and layer-by-layer separation management. Its "over provisioning" and "static connection" (staTIc connecTIvity) characteristics are under this situation. Seemingly inefficient, 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 transmission network is an optical transmission architecture that can be dynamically adjusted by software through flexible and programmable configuration of hardware. Its core technologies include: flexible and variable optical and electrical functional modules, building high-speed, low-power programmable optical systems, supporting Openflow standard control interfaces and open application interfaces (APIs), and using programmable transmission controllers (Programmable Transport Controller) to realize optical network programmability and resource cloudization, so as 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

Software-defined OTN has three major characteristics of "elastic pipeline", "instant bandwidth" and "programmed optical network", which can meet the requirements of rapid deployment of different services in the future, bandwidth allocation on demand, and easy maintenance and management of the network, which can effectively reduce operators. TCO, improve profitability.

Software-defined OTN, four key technologies

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

Flex OTN technology

Traditional OTN uses GMP technology to encapsulate and bear multiple services such as TDM / IP. However, as the service rate increases, the mapping, encapsulation, and framing processing based on the fixed-rate OTUk interface are increasingly unable to meet the operators' requirements for ultra-wideband and Flexible and configurable bandwidth requirements, and different OTUk requires different hardware to correspond to it, and at the same time, it can not be matched with a software programmable optical physical layer (Flex Transceiver) unit. Flex OTN introduces flexible OTN processing on the basis of the original OTN, which is perfectly combined with the programmable optical layer, which not only expands the flexibility of the OTN, but also is compatible with the existing network, which satisfies the flexibility and high efficiency for future multi-services. Of the load.

Flex Transceiver technology

Transceiver is a unit that realizes the mutual conversion of electrical signals and optical signals. Traditional Transceiver has a single hardware structure and different application scenarios require different modulation code types and line rate boards or optical modules. Flex Transceiver uses a general hardware structure. Based on the industry-leading flex-ODSP technology, only a simple software configuration, a mouse click, a set of hardware system can meet a variety of application scenarios, and with Flex OTN and Programmable Transport Controller technology, users can according to the actual situation Business conditions, rationally and optimally allocate optical layer bandwidth resources to achieve fine-grained operation of traffic while reducing overall network power consumption. Similar to the promotion of tunable lasers to optical networks, Flex Transceiver is bound to bring greater changes.

Flex ROADM technology

ROADM is an OADM unit that can be configured. It is an indispensable and important optical layer physical unit in the optical network. It can realize the switching and adding and dropping of wavelength channels on the optical layer. With the advent of 400G / 1T +, in order to further improve the utilization of spectrum resources, the original fixed channel interval was broken, and Flex ROADM came into being. Flex ROADM can achieve a very small bandwidth interval and achieve lossless exchange (hitless) between any optical channels of any bandwidth; combined with Flex OTN and Flex TRX technology, it can further achieve finer sub-wavelength scheduling at the optical layer. Direct layer bypass reduces the use of expensive upper-layer switching equipment and lowers the operator's TCO and overall network power consumption.

Programmable Transport Controller technology

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 forms, achieving end-to-end unified control from dynamic cloud services to flexible pipelines based on Flex OTN, Flex TRX, and Flex ROADM, which facilitates the rapid and instantaneous value-added services. Provided; through the open API with the application layer, the application can drive the network, quickly and instantly reconstruct the network hardware system, and realize the programmable optical network to meet the user's dynamic real-time and personalized service needs; through the centralized control concept To make the business multi-layer traffic dredging more intelligent and controllable, the utilization rate of the entire network resource can be maximized, the end-to-end quality of the business is effectively guaranteed, and the user can get the most perfect experience. This software-defined management method based on centralized management, standardized control, and open API has transformed the transmission network from a dumb pipeline to an intelligent pipeline. As a part of the business, the pipeline provides operators with "OaaS" value-added services (OpTIcal as a Service ).

Software-defined OTN value

Operation and maintenance "easy", operation "fine"

There are many types of boards in the traditional network, which increases the cost of material preparation and operation and maintenance, and increases the operator's Capex and Opex. In the software-defined OTN, Flex OTN, Flex TRX, and Flex ROADM all use a common hardware architecture, which can realize the normalization of single-board hardware; at the same time, because the optical module can be software programmed, custom rate, code type, etc., it provides network operation and maintenance and Operation also brings many benefits. For example, in the project deployment stage, it can reduce the number of spare parts, reduce the technical requirements of the deployment engineers, accelerate the deployment speed, and facilitate the rapid deployment and deployment of services. When it drops, the system performance can be optimized by changing the modulation pattern. The flexible configuration of the board can also bring operators a more flexible bandwidth sales model, further improving revenue.

Bandwidth resource "zero waste", bandwidth value "zero residue"

The "elastic pipeline" of the software-defined OTN makes it possible to refine the management and use of bandwidth resources, and achieve "zero waste" of bandwidth resources. The network controller uses standard control interfaces to reconstruct the optical layer hardware equipment according to the upper-layer service traffic and adjust the size of the pipeline. On the one hand, it can save network bandwidth resources and improve bandwidth utilization. For example, software-defined OTN can increase the bandwidth utilization 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" possessed by the software-defined OTN, in addition to bringing a different user experience, has also realized the "zero residue" of the bandwidth value. Traditional optical transmission network, from the user to send a bandwidth request, to the final business opening, need to go through multiple departments, multi-person processing, the opening time can be up to several months, and through unified end-to-end control, combined with flexible optical physical layer technology To reduce the participation of people, the time for service opening can be reduced to a few hours, or even a few seconds. The rolling use of bandwidth resources not only improves the revenue per bit, but also brings a good ecosystem between ICP and ISP.

The "programmed optical network" of 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 business. By providing an open API, the network capabilities are abstracted to the application layer. At the same time, the application-layer business-driven network establishes connections according to personalized requirements, enabling customers to easily implement self-service network customization based on standardized interfaces and provide services on behalf of maintenance and management. Produce closer and mutually beneficial in-depth cooperative relations with customers and content providers, thereby co-creating profitable growth points.

Adaptive flow and distance

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 passed. For small paths with short spans, you can choose a higher-order modulation format that meets the requirements of OSNR. For the optical path, a low-order modulation format that occupies a large bandwidth but can work normally under low OSNR can be used, thereby more effectively using line spectrum resources and improving spectrum efficiency.

Software-defined OTN is an inevitable evolution

In the era of cloud networking, services are diversified, and traditional optical transmission networks can no longer meet new demands. Efficient, flexible, and open have become the key to the evolution of optical networks. At the turning point of change, Huawei proposed software-defined OTN. Provides real-time bandwidth management, centralized control of virtualized network resources, and open standardized application interfaces on the basis of providing high-efficiency, flexible, and open management and control for new services, so that optical networks can better serve the business, serve the user experience, and help Customers continue to reduce operating costs and develop new profit models to build a healthier and harmonious industrial chain.

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