Application Layer of software-defined network architecture

The goal of SDN is to achieve an idealized enterprise network, separating network control from physical network topology, this creates an environment for sending traffic from the central management controller to all vswitches and routers. In a software-defined network environment, this software-based controller must have end-to-end monitoring capabilities for network resources and capacity.

Through the network end-to-end view, the SDN controller can become a special operating platform for network applications and services.OpenFlow is an advanced specification that supports software defined networks, but OpenFlow specification does not fully determine how software defined networks support these advanced networks.The solution begins with the software-defined network architecture, which is the foundation of OpenFlow applications.

Kyle Forster, one of the founders of Big Switch Networks, pointed out that with the development of software-defined Networks, suppliers and enterprises will adopt a three-tier architecture. The first layer of the architecture is physical network devices, including Ethernet switches and routers. The intermediate layer is composed of controllers. network devices that forward traffic are used to learn enterprise information such as capacity and requirements. They start and stop traffic. The top layer is some applications that use controllers for security, management, and other special functions.

"Suppliers must have one to two layers, or even multiple layers," Forster said ." He pointed out that Big Switch focuses mainly on the controller and application development layer ."

At the same time, Big Switch and other vendors are cooperating with third parties to develop Controller Applications to implement specific security, management and other functions.

Forster says these controller-based applications have the current functionality of physical network devices. For example, a network architect responsible for building a Software Defined network can deploy applications such as Virtual Server Load balancer, Virtual Intrusion Prevention System (IDS), and virtual firewall on the controller. These Applications check the Controller information, including the traffic mode, application data, and capacity. If the IDS application detects malicious traffic on the traffic processed by the Controller, it isolates these packets before they infect the network.

Glen Hunt, Chief Transport and routing infrastructure analyst at Current Analysis, pointed out that the market for software-defined network applications is not yet taken shape, but the OpenFlow architecture can provide some important information for Controller Applications. This information can be used in a more flexible, efficient, and secure network environment.

Software-defined network devices: promoting cloud computing

Hunt pointed out that cloud computing applications may significantly benefit from software defined networks and OpenFlow, because these technologies greatly simplify Resource Allocation in multi-vendor virtual environments. The Controller-Based Server Load balancer application can automatically migrate workloads between virtual machines using a large amount of capacity information about each network device in the controller.

Controller-based applications are similar to virtual network service devices deployed on virtual machines, but they have higher scalability, flexibility, efficiency, and manageability compared with conventional models using physical devices.

"From the Perspective of service providers, through optimization to reduce overload, OpenFlow can also provide better services to end users," Hunt said ."

Software Defined Network: How will traditional network providers get involved?

Although controller vendors such as Big Switch encourage the development of application layers of software-defined networks, it is still unclear how routing and switching suppliers adapt to this trend. These suppliers rely primarily on network-based applications and features to implement their respective hardware. So how do they maintain competitiveness in Software Defined networks? Mike Spanbauer, Chief Analyst of Current Analysis's enterprise network and data center technology, pointed out that the answer to this question is actually very simple.

"Most network equipment vendors can still develop custom software," Spanbauer said. OpenFlow runs in parallel or adjacent to the native operating system as a supplement to the existing control panel ."

Juniper recently opened the OpenFlow driver source code for routers and switches to developers using Junos software development kit, allowing third-party developers to test controller-based applications of software-defined networks. Other vendors will also follow Juniper's approach, Hunt said.

Of course, it is still unclear what the OpenFlow system is. However, it is clear that the existing exchange and routing suppliers will not yield to the Controller suppliers or any competitors-at least they do not want. In other words, Innovators need to build a complex and rich ecosystem, but innovation is not enough.