Software Defined Network (SDN) is a new type of network architecture that implements separate network control and forwarding to form a logically centralized unified controller.In turn, the software programmable interface is opened on the controller for service call, and the purpose of flexible configuration of the network is achieved.In the cloud computing data center, providing virtual resource services is its most important technical realization, and the network is also provided as a service to customers.The network needs to provide dynamic, on-demand, isolated network environment and custom network service chain connection services for different users and applications. These are the traditional network architectures that cannot be met, and SDN was born because of this.
Although SDN was not born for a long time, it has been greatly developed. SDN-related startups have sprung up, and traditional network equipment vendors have thrown olive branches to SDN. Major data centers and network operators have launched technical research and various attempts at SDN, with the intention of being able to make a big difference in the era of SDN .SDN already has a relatively complete technical system support, and the Openflow protocol is the core technology of its implementation.However, because everyone has different understandings of SDN, the implemented controller software can only control their own hardware devices, and can not form generalized software.This is also achieved in order to get competitive advantage, exclude other software manufacturers, and obtain more markets, which makes SDN technology landing slower, affecting the development of SDN to some extent.Even so, SDN is still developing rapidly in technical theory, and soon it also has SD-WAN and SD-branch.
The full name of SD-WAN is a wide-area software-defined network. In 2015, it became a hot topic in SDN technology, and the first SD-WAN product appeared on the market.SD-WAN inherits the concept of SDN control and forwarding separation and centralized control. It deploys SDN technology in WAN network, mainly uses software advantages to improve network performance and reduce cost, while ensuring security and stability and easy deployment.The basic principle of SD-WAN can be understood as establishing a “virtual network” on top of one or more different physical networks or network services, as long as the mapping between virtual and physical can be done.There is no need to know what technology is being used for things inside and outside the virtual network.In the past, we mentioned that SDN is mainly used in data centers and LANs, and SD-WAN extends SDN to WANs.There are many protocols in the WAN that are different from the Ethernet protocols in the LAN, so it is not a simple migration, but a specific design for the WAN.SD-WAN can operate by measuring basic network traffic metrics such as latency, packet loss, jitter, and availability. With this data, SD-WAN can actively respond to real-time network conditions and select the best path for each packet.SD-WAN has a central controller concept for global network visibility.Network administrators use the controller architecture to create policies and allow the system to take action without explicit manual change control.This controller platform performs policy-based forwarding based on current WAN conditions and complete information on enterprise application preferences, enabling immediate global changes without the need to manually log in to each router.
- SD-WAN is focused on providing software-defined application routing for WAN or WAN, as well as connecting geographically distributed locations (headquarters, data centers, branch offices, remote and mobile users), national or global bases. On the other hand, SDN is mainly concentrated in the LAN (local) or the core network of the service provider.
- SDN can be fully programmed by the customer or user and allows for efficient change and configuration management. Although SD-WAN is built on SDN technology, SD-WAN vendors handle programming behind the scenes, eliminating the complexity of end users.
- SDN focuses on the internal network, whether it is a LAN or a core service provider network. While SD-WAN is focused on connecting the network to the user over the WAN.
- SDN is supported by NFV, Network Function Virtualization, which provides a variety of virtualized network functions through software that have been built into proprietary closed systems to date.In contrast, SD-WAN provides software-defined application routing that can be virtualized or virtualized or run on SD-WAN devices.
The technology behind SD-WAN changes the paradigm from a packet-based network routing system to an application-based routing system.This enables organizations to use consumer-grade broadband Internet with improved quality and performance, and importantly, the cost per megabyte is lower than the cost of using MPLS previously.SD-WAN also provides flexibility and flexibility while maintaining centralized, predefined business policies and controlling the way applications are routed. The resulting visibility and control allows you to identify applications running on the WAN and set policies for their priority and usage.SD-WAN also uses dynamic WAN selection to route these applications through the best performing path.In addition, SD-WAN allows you to use multiple available links in an “active/active” configuration to provide load balancing and failover with virtually no perceptual disruption. Traffic between sites flows through dynamic, fully encrypted tunnels and can be segmented to provide a high level of security.
SDN is no longer an Ethernet network technology, but all network protocols rely on its development technology, such as storage networks. Software definition concepts have been introduced early, and almost all aspects of the data center are related to software definition. .SDN technology is a global and disruptive network transformation technology. It uses IT technology to transform traditional closed networks, which brings opportunities for network development.
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