Shulou(Shulou.com)06/02 Report--

"data center is the core supporting platform of cloud computing, and the development of cloud computing has posed a severe challenge to the data center network architecture. The traditional electrical interconnection network architecture is difficult to meet the requirements of cloud applications in terms of bandwidth, equipment overhead, energy consumption, management complexity and so on. Therefore, the optical interconnection network architecture characterized by low energy consumption, low overhead and high bandwidth has emerged and attracted wide attention of researchers." What is optical interconnection with the process of digitization, data processing, storage and transmission have been developed rapidly. The demand of high bandwidth makes short-distance interconnection become the bottleneck of system development. Due to the influence of factors such as loss and crosstalk, the transmission distance of high-bandwidth interconnection based on copper wire is limited, and the cost increases. And too many cables will also increase the weight of the system and the complexity of wiring. Compared with electrical interconnection, optical interconnection based on multimode fiber has many problems, such as high bandwidth, low loss, no crosstalk, matching and electromagnetic compatibility, and has been widely used in high-speed interconnection between cabinets, frames and boards. According to the third-party report of Synergy, it is predicted that by the end of 2019, the number of super-large-scale data centers in the world will exceed 500. by that time, 83% of public cloud servers and 86% of public cloud loads will be carried in super data centers. The proportion of super data center server deployment will increase from 21% to 47%, processing capacity from 39% to 68%, and traffic from 34% to 53%. Data center network structure after the internal interconnection rate of the data center network rises to gigabit, optical interconnection is widely used because of its advantages such as bandwidth, connection distance and easy deployment. With the expansion of the network scale, especially with the development of cloud business, east-west traffic increases sharply, accounting for about 70% of the total traffic. This makes the number of network nodes in the data center more and more, and the types of interconnection ports become more and more abundant. The number of optical modules used in the data center is growing exponentially, the impact of optical interconnection on the stability of the network system is increasing day by day, and the proportion of the network hardware cost is also considerable.

Example of interconnection in data center network the application scenarios of network equipment interconnection are becoming more and more abundant, and the technical solutions of optical modules are developing continuously, from traditional discrete devices and compound semiconductor chips to optical integration PIC and silicon-based photonic SiP. Optical interconnection technology has always developed in the direction of high speed, integration and low power consumption according to Moore's Law. The following figure lists the evolution routes of module types used in the data center. In the face of many types of optical modules and interconnection schemes, it is necessary to choose flexibly according to the service requirements carried by the network, so as to optimize the network performance and reduce the comprehensive cost at the same time.

Although the optical transceiver module is originally designed to be pluggable and standardized, for the sake of deployment habits and system compatibility, network equipment manufacturers often bundle the optical module with equipment to provide data center users. The end user can only passively accept the optical module type and technical scheme chosen by the network equipment manufacturer. However, with the gradual increase of the network size of the data center, the network architecture becomes more complex and diversified, and the autonomy of technical solutions and the pressure of cost reduction drive us to decouple the binding of optical modules and network devices. Furthermore, with the opening of the network and the white-box of network equipment, it is imperative to introduce customized optical modules independently.

Jingdong cloud data center optical interconnection practice unified technical standards to solve the problem of compatibility between optical modules and network equipment, simplify network construction and operation and maintenance as pluggable components, optical modules to adapt to different types of network equipment from different manufacturers, this requires unified technical indicators to achieve the widest range of compatibility. As a technical specification of optical module generally followed in the industry, MSA defines the basic rules such as electrical characteristics, connectors, management interface and mechanical structure. However, the restrictions of MSA are relatively loose, and different manufacturers are different in the specific implementation. Network builders need to improve and refine the technical requirements according to their own application needs and operation and maintenance habits, not only for optical modules, but also for network equipment optical ports. Customized function optical port adaptive control to reduce failure rate

As the builder and user of the network, we combine the network equipment with the optical module to realize the dynamic automatic adaptation of the optical module and the network equipment from the system level. Based on the error check of the data link layer at the device end, the signal integrity parameters of the optical module and network equipment are automatically adjusted to form a forward feedback mechanism. On the basis of not increasing the hardware cost, the optical link failure caused by signal integrity mismatch is reduced.

The optimization scheme reduces the system cost and authentication cost a) according to the deployment of the network, the optical interconnection scheme is flexibly selected from many optical interconnection schemes to meet the application requirements while minimizing the comprehensive cost. Taking 100G node interconnection as an example, several mainstream schemes are compared according to different connection scenarios in order to achieve the optimal performance-to-price ratio. B) cooperate directly with the module / equipment manufacturer, make full use of the manufacturer's technical resources, construct the optical module function and reliability certification system, and simplify the supply relationship. Advantages of openness and customization

The optical module is decoupled from the switch, and the technical scheme of optical interconnection is chosen independently to adapt to the network iteration.

Unify standards, solve the problem of compatibility between optical modules and network equipment, and simplify network construction and operation and maintenance

Customized electrical characteristics and management interface to reduce failure rate and operation and maintenance costs

Cooperate directly with optical module manufacturers to guide technical solutions and reduce costs

Data center optical interconnection technology has great potential to solve a series of problems faced by cloud computing networks. Although there are still a series of problems to be solved in this field, it can be expected that with the maturity of optical devices and in-depth research, the data center optical interconnection architecture with low cost, low energy consumption, high bandwidth and low delay will strongly promote the development of cloud computing technology.

references

[1] https://www.gigalight.com/cn/solutions-671.html[2] https://product.pconline.com.cn/itbk/life/electronic/1802/10849054.html[3] "Optical Interconnection Network in Cloud Computing data Center: research status and trend" http://cjc.ict.ac.cn/online/bfpub/04398-%E4%BD%99%E6%99%93%E6%9D%89-2015522113801.pdfRECOMMEND recommends reading JD.com network Open Road-- Exploration and practice of self-developed switches heterogeneous de-stacking | A perfect scheme to improve the high available SLA of the network

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