The definition of SDN

Software-Defined Networking, is a new concept or framework designed to make data networks more flexible, easier to operate and manage, and better able to respond to applications development and network conditions changing needs, and cost control .


Three kinds of methods to implement SDN:

  1. Openflow: Currently the most well-known method is defined by ONF and promotion of SDN / OpenFlow, separate the forwarding and control plane which exist in the same network switch device, and move the control plane to a separate device called a controller, is responsible for calculating the network best optimal path through a standard protocol control switch device for particular stream forwarding behavior.
    This SDN is approach's core technology is OpenFlow, to standardize the communication protocol between network switch and the controller. OpenFlow is promoted by the non-profit organization Open Network Foundation,ONF , and led to the use of OpenFlow as a controller architecture standards. ONF has more than 70 members, comprising service providers, large network equipment manufacturers and start-ups. Using ONF's SDN architecture's main advantage is that it has a protocol OpenFlow industry standards, as well as numerous vendor support.

  2. Virtual networking: Adopt separate control and forwarding planes, launched by a particular vendor's controller and switch device. Normally coexist with existing network equipment also called (overlay) mechanism, using VXLAN (Virtual Extensible LAN) or NVGRE (Network Virtualization using Generic Routing Encapsulation), etc., as the framework agreement. This approach may attract large enterprise customers, who have already using large network devices and virtualization device, but its application is limited to the management of hypervisor-based virtual switch within a virtual host management program, and the VXLAN and NVGRE still emerging technologies not yet become IETF standards.

  3. API: Directly through programmable interface (API) to control devices on the network, it can be controlled on a broad definition of criteria, including OSI stack from layer2 to layer7 all devices. This method is has not separate the control plane and forwarding plane, the control plane is not set. Currently this way is provided by the existing network equipment manufacturers in response to SDN trend.

Three value positions of SDN

  1. SDN definition of infrastructure can respond to the entire Layer 2 to Layer 7 business logic.
  2. SDN enables the network to understand the needs of the application process and computing resources, and dynamically provide the necessary network resources.
  3. Through automated configuration management, SDN provides better control of infrastructure, management and security.

Value orientation 1 and 2 in the near future will attract such large scale data centers, public cloud service providers and Internet service providers inputs. Value position 3 is the subject of all the different sizes of organizations and enterprises common concern. In addition to reducing costs, automated management, and security policies implement and other specific applications SDN enterprises, but also to provide better results than the traditional way of implementation, including:

  • Network virtualization
  • Load balancing
  • Firewalls
  • Distributed denial of service prevention
  • Traffic engineering
  • Disaster recovery
  • Application acceleration via techniques such as SSL offload
  • Web optimization
  • Network analysis whereby management data is filtered from network elements and sent to a central site for analysis

The advantages of SDN

  1. According to InformationWeek 2012 research on software-defined network, IT organizations believe that SDN can help them overcome a series of challenges, such as improving utilization and network efficiency, increased automation of routine tasks and improve safety. SDN can also reduce costs.
  2. SDN also promote the use of the software interface, allows the import third-party applications to improve network services, or even become a new Internet service, SDN can span a variety of different devices, such as Switch, Router, Firewalls and Load balancing, etc., coordinate resources integration and collaborative operation.