what is sdn network

what is software defined network (SDN)

Software defined network main target is to get the program ability to the traditional network. In SDN one of the main functions is to network function virtualization. Mostly SDN networks used by the large networks such as Google, Microsoft, amazon cloud service IBM etc.

In the Figure 1 shows the traditional network vs SDN network. In the SDN network Firewall and the load balancer in the cloud environment they are SDN support devices.in the traditional network firewall, load balancer and the web server in the local promises.

Figure 1: Difference between traditional network and SDN network 

In the SDN it separate the control plane and data plane Figure 2, Control plane is a logic that control the packets (decision part of the device) and the data plane is hardware part of the device.

Control Plane ---- Logical part

Data Plane     ---- Hardware part

Figure 2: Control plane and Data plane

Comparison between traditional network and software defined networks

Figure 3 : Comparison between traditional network and software defined networks

CONTROLLER

Controller is the device that controls and manage the network. Network controller connects all devices. When in the managing aspects it is easy to control. In software defined networking we can dynamically change the routing only need to change the controller.(EX: Cloud environments AWS ,azure google cloud etc.).In the separation of the control plane and data plane it provide the centralized control with Programmability. The communication happens between controller and the networks elements using open-flow protocol.

SDN Controller Provides

• Management of network state

• High level data model captures the relationship between resource

• Provide secure TCP session between controller and associated agents

• provide the mechanism to discover the network  

Active network     - changing the behavior of the network according to the packets. In active                                                networks security is low because data and instructions in the same packets.

Passive network  - It will not change the behavior of the network according to packets

OPEN-FLOW

Open flow protocol work in data-link layer and transport layer in the ISO/OSI seven-layer architecture. It works with TCP protocol with 6633 and 6653 ports.

Reactive flow insertion -- When packet come to the switch it ask instruction from controller.Not mush effective method always witch must talk to the controller and ask for the instructions to execute.

In the open flow it maintain the flow table(same as the MAC table in traditional switch). In this table contained the actions to follow. Actions such as Forward packet to the port, Encapsulate and forward to controller , Drop packet ,Send to normal processing pipeline and modify fields. When first time packet came, switch will ask from controller and set to the flow table. In the 2nd time packet come firstly it will check the flow table if match found it will forward the packet if not switch will ask form the controller.

Open flow table contained 

• Match Filed (Source MAC, Destination MAC, Ethernet type etc. )

• Priority

• Counters

• Instructions (Drop, Forward, Modify etc)

• Time out