Software Defined Networking (SDN)

Tarunianand MuruganandanPranav Kumar Sivakumar

Three Planes

● Control Plane (brains or decision maker)

● Data Plane (packet forwarder)

● Management plane

Networking Overview

● Physical layer

● Data link layer

● MAC address

● Network layer

● IP address

● Port

● Frame, packet

● Switches, routers

● Broadcast/flood

Networking functionality migrating to Hardware

SDN

● In conventional networking, all three planes are implemented in the firmware of routers

and switches.

● Software-defined networking (SDN) decouples the data and control planes, removes the

control plane from network hardware and implements it in software instead, which

enables programmatic access and, as a result, makes network administration much more

flexible.

● An architecture to control not just a networking device but an entire network

Why SDN?

SDN separates the control of the network from the hardware. It

uses software applications to program your network intelligently

through centralized control. This means the underlying hardware

and associated technologies are still there, but they are

programmed centrally.

As a result, you can consistently and holistically manage your

entire network with utmost flexibility and speed.

SDN Architecture

Properties of SDN Architecture:

● Plane Separation

● A simplified device

● Centralized control

● Network automation

● Virtualization

● Openness

How does SDN work?

● Controllers

● Southbound APIs

● Northbound APIs

What are SDN controllers?

● Control point that manages flow control between SB and NB APIs

● When there are multiple SDNs, controllers also federate between each other using

application interfaces like open flow

● General tasks: inventory of devices network stats, orchestrating rules through the

network etc.

● Commonly used protocols - OpenFlow and OVSDB

What are SDN southbound APIs?

● APIs that communicate between controller and switches/routers of the network

● Dynamically make changes according to real time needs and demands

● Common SB APIs: OpenFLow, Lisp, XML

What are SDN northbound APIs?

● REST APIs that communicate between the controller and services/applications that run

over the network.

● Facilitate efficient orchestration and automation of the network to align with different

application needs

● Used to integrate controller with automation stacks and orchestration platforms

● Common NB APIs: load balancers, firewalls, SDSec devices

SDN controllers

● The first SDN controller - NOX by Nicira Networks (Claimed to be base of Google WAN)

● The first open source controller - Beacon (Java based OpenFlow)

● Others include Trema (Ruby based), Ryu (supported by NTT)

● Proprietary controllers like Cisco, HP and IBM (originally based on Beacon)

● Current shift to OpenDaylight

OpenDaylight - New, open source controller

● Oxygen - the 2018 release

● Java based, derived from Beacon

● New P4 plugin and Kubernetes plugin for mixed VM-container environments

● ‘Managed distribution model’

● Security - Authorization, authentication and accounting

● Each component is isolated as a Karaf feature to prevent interference

● Uses OSGi and Maven to manage the Karaf feature interaction

SDN Application Responsibilities

● Configure flows to route packets through the best path between two endpoints

● Balance traffic loads across multiple paths or destined to a set of endpoints

● React to changes in the network topology such as link failures and the addition of new

devices and paths

● Redirect traffic for purposes of inspection, authentication, segregation, and security

related tasks

Do you need an SDN?

● The industry in which the organization is operating

● The size of an organization’s network

● The dynamic nature of an organizations’ applications and workloads

● The number of VMs within an organization’s network

● The organization’s need for agility, flexibility and scalability within the network

● The organization’s need to simplify security measures and control access to applications

● The organization’s access to personnel and capital resources

Advantages/Features

● Programmable networks

● Intelligence and control centralized

● Network interaction via APIs

● Vendor-neutral architectures

● Dealing with big data

● Supporting cloud-based traffic

● Managing traffic to many IP address and virtual machines

● Making infrastructure scalable and agile

● Managing policy and security

OpenFlow

General Myth:

SDN is OpenFlow

Reality:

OpenFlow is an Open API that provides a standard interface for

programming the data plane switches

Why OpenFlow?

SDN requires:

● That there must be a common logical architecture in all switches, routers, and other

network devices to be managed by a controller

● A standard, secure protocol between the SDN controller and the network device.

OpenFlow is both, a protocol between SDN controllers and network devices, as well as a

specification of the logical structure of the network switch functions.

OpenFlow (contd.)

● OpenFlow can be compared as an x86

instruction for the network nodes

● Provides open interface to ‘black box’

networking node (routers and L2/L3 switch) to

enable visibility and openness in the network

● Control plane and Data plane are separated

like,○ The Data path of the OpenFlow switch consists

of a Flow Table and an action linked with each flow entry

○ The Control path consists of a controller which writes the flow entry in the flow table.

All SDN Alternatives

● OpenSDN

● SDN via APIs

● SDN via Hypervisor - Based Overlays

● This approach tends to be focused around OpenFlow , which is considered to be one of

the first SDN standards, and allows a SDN controller to directly interact with network

devices (routers, switches, etc.)

● OpenFlow is just the protocol, so you could have Open SDN with other protocols if you

choose.

OpenSDN

SDN via APIs

● SDN implementation via APIs refers to southbound APIs that configure and program the

control plane active on the device.

● OpenFlow is used to directly control the data plane, not just the configuration of the

devices and the control plane.

● Some of the API vendors are: Juniper Networks, Cisco , Arista and OpenDaylight

SDN via Overlays

● What are overlay networks?

● What is a hypervisor?

● So what does SDN have in unique?

Challenges to SDN

● Coordination between applications

● Lack of standard NB API

● Flow prioritization

References

● https://www.datacenterknowledge.com/archives/2013/07/26/7-software-defined-netw

orking-considerations

● https://www.sdxcentral.com/sdn/

● SDN Architecture, Open Networking Foundation, ONF TR-502, Issue 1

● Software-Defined Networks and OpenFlow - The Internet Protocol Journal, Volume 16, No. 1,

Stallings● Software Defined Networks, The Elsevier Inc, 2014, Gornasson, Black● Software Defined Networking with OpenFlow, Packt Publishing, 2013, Azodolmolky● https://infocus.dellemc.com/javier_guillermo/