What does the router belong to in the three-tier architecture of SDN?

In the three-layer architecture of SDN, routers belong to the "infrastructure layer". The infrastructure layer of SDN architecture consists of physical switches in the network that forward network traffic to their destinations. The use of SDN is sometimes referred to as an adaptive or dynamic mode of operation, in which the switch issues routing requests to the controller for packets that do not have a specific route. This process is separate from adaptive routing, which passes through routers and is based on the network topology. algorithm rather than issuing routing requests through the controller.

The operating environment of this tutorial: Windows 7 system, Dell G3 computer.

What is SDN?

Software-defined networking (SDN) is an architecture that abstracts the different, distinguishable layers of the network to make the network agile and flexible. The goal of SDN is to enable enterprises to and service providers can quickly respond to changing business needs to improve network control.

In a software-defined network, a network engineer or administrator can shape traffic from a central console without touching individual switches in the network, regardless of the specific connections between servers and devices. Centralized SDN control The controller will direct the switch to provide network services wherever needed.

This process is different from traditional network architecture, in which individual network devices make traffic decisions based on their configured routing tables. SDN has been playing a role in networks for ten years and has affected many networks. Innovation.

SDN Architecture

The typical representation of SDN architecture includes three layers:

• Application Layer

  The application layer contains typical network applications or functions used by an organization, which may include intrusion detection systems, load balancing, or firewalls.

  Traditional networking would use specialized appliances such as firewalls or load balancers, while software-defined networking replaces appliances with applications that use controllers to manage the behavior of the data plane.

• Control Layer

  The control layer represents the centralized SDN controller software that acts as the brain of the software-defined network and resides on the server and manage policies and traffic across the entire network.

• Infrastructure Layer

  The infrastructure layer consists of the physical switches in the network that forward network traffic to their destinations.

How SDN works

SDN encompasses multiple types of technologies, including functional separation, network virtualization and Automation through programmability.

Initially, SDN technology only focused on the separation of the network control plane from the data plane. While the control plane decides how the packets should flow through the network, the data plane moves the packets from one place to another.

In a classic SDN scenario, a packet arrives at a network switch, rules built into the switch's proprietary firmware tell the switch where to forward the packet, and these packet processing rules are sent from a centralized controller to the switch.

The switch (also known as the data plane device) queries the controller for guidance as needed and provides the controller with information about the traffic it handles. The switch sends each packet along the same path to the same destination and handle all packets the same way.

Software-defined networking uses an operating mode sometimes called adaptive or dynamic, in which the switch issues routing requests to the controller for packets that do not have a specific route. This process is separate from adaptive routing, which Routing requests are issued through routers and algorithms based on network topology rather than through the controller.

The virtualization aspect of SDN works through virtual overlays, which are logically independent networks on top of the physical network. Users can implement end-to-end overlays to abstract the underlying network and segment network traffic. This micro-segmentation It is particularly useful for service providers and operators with multi-tenant cloud environments and cloud services, as they can provide each tenant with a separate virtual network with specific policies.

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