What is "Software Defined Network (SDN)?"


Introduction:Software Defined Network (SDN) is a network architectural , where control plane is is decoupled from hardware and implemented as a software application.This is text book definitions, in order to understand about, we need to get back to network program fundamentals.

OSI Layer : Basics

This is seven layer protocol. Each has one layer.

Source: whatis.techtarget.com

Layer1:  This Physical Layer

Layer 2:  Data Link layer.

As name suggests it simply looks at MAC address and route it to them.  switch performs at layer-2

Test Lab Automation: Physical Layer Switches
Switches (source: mrv.com)

Switch: It is device that channels the incoming from any of the multiple input ports to specific output port. This output port connects intended destinations .  Switch will connected at “Layer-2”

Layer 3 refers to the Network layer of the commonly-referenced multilayered communication model, Open Systems Interconnection (OSI). The Network layer is concerned with knowing the address of the neighboring nodes in the network, selecting routes and quality of service, and recognizing and forwarding to the Transport layer incoming messages for local host domains.

In Layer3 “Router is used to connect two networks together

The above diagrams refers to routers/switches.

Router can be viewed as following :

However, the main focus of a router’s operation remains the network layer. Its functions can be separated into three categories:

Control plane—Handles the router’s interaction with the other network elements, providing the information needed to take decisions and control the overall router operation. This plane runs processes such as routing protocols and network management. These functions are generally complex.

Data plane—Handles packet forwarding from one physical or logical interface to another. It involves different switching mechanisms such as process switching and Cisco Express Forwarding (CEF) on Cisco IOS software routers.

Issues in Hardware implementations of Router/Networks?

Problem Statement:
1. When you want to view Video posted on web. The data will arrived by from hosting server . All the way it hits via several networking hardware.
2. In between router /switches not helps you for flow of the data, but also it controls (speed, routing alogorithams , switching and so on.
3. In above steps are controlled by hardware architectural (which in inbuilt in specific routers/switches or FPGs programming or what ever)
This is pretty  tightly coupled architecture. And also in entire hardware .Rather than control happens in hardware, it will faster if the it done by software program.

Software Define Network

SDN (source: layerzngn.com)

As above SDN inserts a new layer software between hardware and software controlling it .  So IT people can write Applications to control the hardware and much faster service.

Hope you got the concept. Based on your feedback, will write more articles on this subject.

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