SOFTWARE-DEFINED NETWORKING(SDN)

A New Approach to Networking

Anju Ann JosephSemester: VII Batch: C

B-Tech Seminar Sept 2013

2

Seminar OverviewIntroduction

Why we need new approach?

Why not traditional networks?

SDN Architecture

OpenFlow Approach

Virtual Network Overlay Approach

Challenges & Future Expectation

Conclusion

3

Introduction

Software Defined Networking (SDN) is an evolutionary approach to network design and functionality based on the ability to programmatically modify the behavior of network devices.

SDN uses user-customizable and configurable software that’s independent of hardware to expand data flow control.

It will make networks more flexible, dynamic, and cost-efficient, while greatly simplifying operational complexity.

4

The Need for a New Network Architecture

Changing Traffic Pattern

The Rise of Cloud Services

Consumerization of IT

“Big data” means more bandwidth

Perc

enta

ge o

f net

wor

k tr

affic

Control plane: Routing algorithms

5 Management plane:

Configure basic activities

Data Forwarding plane:

Packet streaming

Traditional Computer NetworksData flow is controlled by switches and routers and contains the following basic elements:

Traditional Networks worked well…

6

Hardware based networks have historically shown that they were stable and reliable.

Operational capacities were quickly regained after a power loss, without significant external interventions.

Operated consistently in varying environments.

But..

7

1

2

Limitations of Current Networking Technologies

Complexity that leads to Static Nature

Inconsistent Policies

Inability to Scale

Vendor Dependence

3

4

So we need something NEW!

Introducing Software-Defined Networking

8

Software Defined Networking (SDN) is an emerging network architecture where network control plane is decoupled from

forwarding plane and is directly programmable.

Lead by Open Networking Foundation(ONF)

SDN-enabled control plane allows the underlying infrastructure to be abstracted

Network appears to the applications as a single, logical switch entity

SDN Architecture

OpenFlow Switches

9

SDN Control Software

Business Appl Business Appl Business Appl

Northbound API

Southbound API(eg. OpenFlow)

INFRASTRUCTURELAYER

CONTROL LAYER

APPLICATIONLAYER

10

APISpecifies how software components should interact each other.

API’s makes it possible to implement basic network functions like path computation, loop avoidance, routing, security and many other tasks. 

Southbound API

Northbound API

Allows controller to define the behaviour of switches at the bottom of the architecture

Provides a network abstraction interface to the applications and management systems at the top of the architecture

SDN Controller

11

The controller is the core of an SDN network.

By running the control plane as software, the controller facilitates automated network management and makes it easier to integrate and administer applications.

SDN controllers uses protocols such as OpenFlow to configure network devices

It manages flow control to enable intelligent networking.

12

OpenFlow is a protocol that is used to define the communication interface between the control and forwarding layers.

It provides direct access to and manipulation of the forwarding plane of network devices.

Uses the concept of flows to identify network traffic.

Approach

13

OpenFlow-enabled Switch

Controller

Secure Channel

Group Table

Flow Table

Flow Table

OpenFlow protocol

OpenFlow switch

Components:Flow table & Group tablePerform packet lookups and forwarding

OpenFlow channelInterface that connects a switch to a controller

Two types

OpenFlow-hybrid

OpenFlow-only

Pipeline

Pipeline process: Maintains sending of packets between flow tables by matching flow entries.

14

OpenFlow PortsLogically connects each OpenFlow switch

Types of ports: standard logical reserved

OpenFlow Packet header

Version Type Length of Msg Transaction id

0 7 15 31 63

MAC src

MAC dst

IP src IP dst VLAN ID

Src port

Dst port

…. Action Count

Flow Table

15

Inside OpenFlow

Packet arrives at switch

Header fields compared to flow table entries

Forwarded to specified port

DroppedOREncapsulates packets and sends to controller

Controller decides

Drops Make new entry in flow table

OR

Match FoundMatch Not Found

16

Message Types

Controller-to-switch messages• Modify-state• Read-state• Packet-out/in• Barrier• Role-Request

Asynchronous messages• Packet-in• Flow-removed• Port-status

Symmetric messages• Hello message • Echo request/reply

Benefits of OpenFlow Approach

17

Centralized Control

Reduced Complexity through Automation

Higher rate of Innovation

Increased Network Reliability and Security

Use Case: Network Slicing among large Data Centers

18

Large Data centers have to accommodate many access requests, each seeking a unique policy and security requirements.

SDN helps to overcome this by creating logical isolated networks and allow them to be partitioned using slicing technique.

Involves abstraction of control plane management, out of each network device into a centralized controller via OpenFlow protocol, helps isolated networks to grow within themselves and also communicate with other networks.

19

Few vendors who have produced OpenFlow enabled network switches

Few OpenFlow based SDN Controllers

Programmed in C++/Python on Linux framework

Java based controllerFocuses on achieving better performance using multithreading

MX series IBM Rack Switch

20

Virtual Network Overlays(VNO) Approach

It creates a virtual network infrastructure for the underlying physical network.

Using VNO concept, the physical network is partitioned into multiple logical networks that can be individually programmed and managed.

21

VNOs are based on a ‘map-and-encap’ approach:

1. Mapping performed to find the destination address of the packet

2. Overlay device encapsulates the packet within an overlay header

3. Encapsulated packet is forwarded to destination where it is de-encapsulated

Scheme followed by VNO- Tunneling SchemeEx:VXLAN(Virtual Extensible LAN)

22

VXLAN(Virtual Extensible LAN)

It is a tunneling scheme to overlay Layer2 networks on Layer3.

Virtual LANs (VLAN) have similar functioning, but its specifications only allow for up to 4,096 network IDs to be assigned at any given time.

Extends the VLAN address space by adding a 24-bit segment ID (VNI)and increasing the number of available IDs to 16 million.

VNI can differentiate individual logical networks so millions of isolated Layer 2 networks can co-exist on a common Layer 3 infrastructure.

With VLANs, only virtual machines (VMs) within the same logical network can communicate with each other. VXLAN can potentially allow network engineers to migrate VMs across long distances.

Use Case: Multi-tenancy in Cloud Computing Environment

23

In a cloud environment, abstraction of the management layer becomes important to enable more interaction of applications with the networking elements.

The virtual network overlay abstracts the underlying physical network, which allows the overlay to move to other physical networks.

Virtual Network Overlay stack for Cloud

OpenStack

OpenStack Plug-in

Rest API

Virtual Network Switch

Hypervisor

Tenant 1 Tenant 2 Tenant 3

VXLAN

Challenge

24

To support co-existence with existing devices the existing technologies must have additional enhancement.For ex, the existing standard path computation elements in routers are not sufficient, they need to be enhanced.

Future ExpectationTo find a unique SDN approach.

Some Frequently Raised Questions..

25

Why is SDN taking so long to adopt?• Enterprises confused about how SDN will specifically

save them on network costs• No compelling use-cases

Is SDN and network virtualization same?• similar goals• overlapping sets of technologies

Conclusion

26

SDN promises to transform today’s static networks into flexible ,scalable, programmable platforms with the intelligence to allocate resources dynamically.

With its many advantages and astonishing industry momentum, SDN is on the way to become- the new approach for networking.

References

27

[1]:Kapil Bakshi,“Considerations for Software Defined Networking(SDN):Approaches and Use Cases,” IEEE Aerospace Conference, March 2013.

[2]:“Software-Defined Networking: The New Norm for Networks,” Open Networking Foundation(ONF) White Paper, April 2012.

[3]:“Software Defined Networking: A new paradigm for virtual, dynamic, flexible networking,” IBM Systems and Technology Thought Leadership White Paper, October 2012.

[4]: Hyojoon Kim and Nick Feamster, “Improving network management using SDN,” IEEE Communications Magazine, February 2013, pp.114-119.

28

Got any Questions?

29