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This article mainly explains "what is the main development direction of SDN". The content of the explanation is simple and clear, and it is easy to learn and understand. Please follow the editor's train of thought to study and learn "what is the main development direction of SDN".

SDN is a new type of network architecture, its core technology is to separate the control plane from the forwarding plane of the network equipment, adopt the centralized control of the controller to replace the function of the control engine scattered on each network device, and realize the flexible customization of the service by defining an open programmable interface.

DC-centric Network Architecture based on SDN/NFV

As shown in figure (1), the agile network architecture based on SDN/NFV with DC as the center has changed from the past multi-level network architecture centered on administrative / densely populated local network to the optimized DC-centric flattened network architecture, realizing the separation of network transmission and business processing. It enables the cloud operation of the business through NFV technology, and can realize the business to be online in one point in the cloud and open to the whole network. The traditional wide area network and the new DCI interconnection network can be adjusted and optimized automatically according to the business demand by introducing SDN. The hierarchical data center design takes full account of latency and business function requirements. The large scale of the network can consider the three levels of edge data center, regional data center and core data center. The small scale of the network can consider the two-level data center architecture after the integration of regional data center and core data center.

VDC enabled by SDN

DC is the core of the future network. SDN technology can well meet the needs of centralized network management, flexible network multipath forwarding, virtual machine deployment and intelligent migration, virtual multi-tenancy, IaaS and so on, and is very suitable for application in data center network, so SDN technology is first developed from DC, and DC is also the most mature application scenario of SDN. In the process of transforming the traditional data center into a cloud data center, DN focuses on solving two problems: first, unified network planning and unified resource scheduling solve the problem of low utilization of computing and storage devices, reduce CAPEX;, and second, automatic distribution of services solves the problem of long online cycle of business deployment, which is conducive to improving operation and maintenance efficiency and reducing maintenance costs. Through the deployment of SDN, the vDC network solution based on SDN realizes the automatic deployment of business servers across DC, and the unified monitoring and management of services across DC network resources. In addition, compute and storage utilization exceeds 30 per cent by consolidating multiple physical DC resources instead of separately reserving resources for a major customer in a single physical DC.

DCI enabled by SDN

With the gradual cloud of enterprise business, enterprises gradually use operators' cloud services from basic IaaS resources to enterprise basic application systems, and then to core high-throughput computing systems. While reducing costs and obtaining more cloud applications, it also puts forward higher requirements for operators' cloud services, such as high quality assurance, differentiated business differentiation, "0" delay and so on. The DC of cloud services provided by traditional operators cannot meet these requirements through interconnection on the traditional Internet. A dedicated data center interconnection-oriented bearer network with centralized resource management, flexible network adjustment, high speed and low delay is the inevitable choice to solve this problem. DCI enabled by SDN is the core solution to support this network. It is precisely in the process of transition to cloud services that China Telecom took the lead in carrying out the construction of a dedicated IDC bearer network for data center interconnection (figure 2). The construction and positioning of its IDC bearer private network mainly serves the following types of services: the first is to provide cloud companies with self-operated IDC/ cloud service private network, and to provide telecom cloud companies with high-quality vDC bearer through the new high-capacity and high-quality vDC bearer private network. The second is to provide IDC/ cloud + SME IDC/ private cloud integrated carrying capacity to facilitate the expansion of cloud business in the future. The third is to provide dedicated line services for large ICP and third-party IDC/ small and medium-sized ICP.

SDN-enabled IP+ Optical Fusion Network

With the rapid growth of Internet traffic, the telecom industry continues to explore new ways to reduce the backbone network TCO. With the maturity of optical network technology such as ROADM and OTN and the application and promotion of GMPLS control plane in optical network, optical network has become an intelligent network that can schedule resources dynamically. How to effectively integrate the resources of backbone IP/MPLS network and optical network, improve the resource utilization, improve the efficiency of network operation and maintenance, and reduce TCO has become a hot topic of backbone network architecture optimization. In the backbone network, IP bearer technology mainly realizes the shunting and forwarding of IP messages after access, while optical bearer technology can improve the bandwidth capacity of optical fiber and transmit signals reliably over long distances. SDN-based IP and optical cooperative solutions make the two technologies complement each other and give play to their respective advantages under a unified management and control system, so as to make the whole backbone network more agile, efficient, visual, unified and open, and bring high-quality experience to users.

The above figure (figure 3) is a SDN-based IP+ optical collaborative solution architecture, which has five changes compared with traditional IP and optically separated networks:\ 1) deploy RODAM and GMPLS dynamic control planes to achieve flexible scheduling of optical layer resources;\ 2) deploy GMPLS-UNI to achieve automatic interaction of cross-layer information between IP and optical layer and automatic deployment of cross-layer paths, which greatly improves the efficiency of network deployment. \ 3) introduce IP PCE controller and optical PCE controller to realize the function of centralized path calculation and policy management, and greatly improve network utilization efficiency and traffic tuning efficiency;\ 4) introduce multi-layer network service issuing platform to realize unified service configuration and distribution;\ 5) introduce multi-layer planning tools to unify network planning and improve efficiency.

B2B Business Transformation of operators enabled by SDN

From the market analysis, we can see that the income of the traditional voice message business is growing slowly or even beginning to decline, and the growth of value-added services such as home broadband and IPTV is slow, but the enterprise private line business, DC and cloud services are growing rapidly (Table 1), and the market space of this part of business will be as high as 1.5 trillion US dollars in the future. This is a strategic opportunity for operators, especially cloud services, and it is crucial to win the market in the competition in which many OTT participate. Table 1 operator business space and trend business type revenue share development trend voice & SMS & video service 35% ~ gradually reduce broadband service (home fixed network access, mobile Internet access) 20% 10% ~ growth slowing dedicated line service (enterprise CPE+ focus + value added + DC) 20% ~ high growth DC&Cloud (rack hosting, public cloud) (hybrid Cloud) 10% ~ High-speed growth of IPTV and other value-added services 5% ~ growth slows down. Currently, it is very difficult for operators to orchestrate E2E services across multiple business areas. When Direct Connect services are deployed across management-separated networks, the deployment cycle is long, inefficient and difficult to adjust. SDN is to solve the contradiction between the business requirements and the traditional network architecture. SDN enables the network to adjust as quickly as IT applications and achieve rapid deployment of new services. Operators need to combine their advantages in the field of WAN with cloud services to enable one-stop ICT services through SDN to enhance their competitiveness in the enterprise ICT market. At present, the industry generally focuses on how to provide enterprises with dedicated line connectivity similar to traditional MPLS VPN through IP technology, and at the same time simplify the complexity of VPN deployment, and achieve enterprise dedicated line connection anytime and anywhere. Before the IP/MPLS wide area network is modified by SDN, a gateway supporting VxLAN can be deployed on the enterprise side through VxLAN Overlay technology to provide on-demand wireless connection for enterprise customers, while seamless connection between enterprises and DC can be realized. After the future IP/MPLS wide area network transformation supports SDN, the deployment of Overlay and Underlay can be implemented to provide higher quality enterprise private line services (figure 4).

PoP Point Reconstruction enabled by SDN/NFV

PoP is the service provider of operators and the key point of rapid service innovation, but the traditional telecom equipment is proprietary hardware + software and closed business system, which makes the service launch complex and innovation slow. Operators are unable to cope with the highly open business competition of OTT players. Therefore, an important original intention of PoP point reconstruction enabled by SDN/NFV is to build an open network, speed up the launch of new services and improve the ability of innovation. The refactoring of PoP points is mainly the work of NFV of business functions. However, since many of the service functions (vBNG/vCPE) of the PoP point are connected with the user layer 2 of the access side, it is necessary to consider how to introduce user traffic from the access network to the VNF while retaining the layer 2 access point information. The current common practice in the industry is to deploy a PoP Gateway at the PoP point to undertake the NFV gateway function (you can choose the software form or hardware form running on the server / VM according to the traffic) Block the interdependence and influence between the NFV network and the underlying network (figure 5).

The purpose of PoP point refactoring is to introduce a software-defined chain of business (Service Chain). Business chain refers to a series of network value-added processing for specific users or traffic, such as website filtering, virus scanning and so on. The implementation of business chain requires SDN technology to achieve flexible business chain definition and user policy combination.

SDN enabled Transport Network (T-SDN)

Software defined Optical Network (SDON) is to apply the concept and technology of SDN to optical network to build a new generation of service-oriented optical network architecture. By decoupling control and transmission, shielding the physical and technical details of optical network, SDON simplifies the existing complex and private control management protocols of optical network; adopts centralized control strategy to improve the intelligent scheduling and cooperative control ability of optical network; through open network interface, it provides the programmable ability of optical network to meet the development needs of future network virtualization, flexible and fast service provision, network and service innovation. Different from the data network, the optical network itself has the characteristics of centralized management and connection-oriented switching mechanism, so the optical network naturally has the characteristics of some SDN, which is easier to evolve to the direction of SDN.

Thank you for your reading, the above is the content of "what is the main development direction of SDN". After the study of this article, I believe you have a deeper understanding of what the main development direction of SDN is, and the specific use needs to be verified in practice. Here is, the editor will push for you more related knowledge points of the article, welcome to follow!

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