Or what is it all about anyway

1. What is SDN? 2. SDN architecture3. SDN Flavors4. SDN and WiFi5. Examples

§Software was always an important part of networking

I run on software!

Script

• SSH to device• show config• parse output• set ip ...

Is this SDN? What about this?

§Problem• Networking currently lacks fundamental abstractions• As a result, networks are hard to manage• Networking product cycles are much longer than common software

product cycles

§Solution• Abstractions simplify and speed up service development• SDN proposes global network view abstraction• Make network evolution more like software evolution

DEFINITION: SDN is an abstraction layer that enables rapid service development that is independent from the underlying, often complex infrastructure.

• Operations/business support systems (OSS/BSS) can not cope with complexity of today’s networks

• VLAN management in large data centers has become a nightmare• Managing backbone networks is ineffective and costly

§ Google Example:- Traffic Engineering (QoS predictability, application awareness…)- Improved Routing (better topology awareness, faster convergance…)- Improved Monitoring

• Single view of the network • Northbound programming interfaces• What is important is the architecture

Abstract Network View

Network Operating System

Control Program

Global Network View

Device Control

ProtocolsProtocolsProtocols

Service Layer/Application Layer)

Control Plane

Data Plane

§Support rapid Service and Application development• Service and Application development should be independent from the

underlying infrastructure• Well defined and open programming interfaces are required

§Separate control from data forwarding• Translate between Service and Application requirements to device

specific configuration• Implement open protocols to support devices from multiple vendors• Forwarding decisions should be flow-based

§Centralise control• Provide a single view of the network• Provide a single interface for Services and Applications• IMPORTANT: the control plane is logically centralised. Even in case of

OpenFlow controllers, it is physically distributed (performance)

RouterFirewall

L3 Switch

L3 Switch

Network Operating System

Campus Router App

Firewall App

Internet Router App

Traffic Policy App

Today

SDN

Switch

SwitchSwitch

Switch

Today

SDN

It’s the app!

It’s the network’s

fault!

It’s the app!We need to talk…

• An interface between the control and forwarding plane- Essentially it is like an API- The SDN controller uses it to manipulate the state of

forwarding plane elements• Needs to be supported on the switch

- The switch maintains flow tables- Each rule identifies a portion of network traffic and what

needs to happen to it • Requires an application to do anything useful

- An application uses APIs on the SDN controller - APIs are typically REST and NOT OpenFlow- The application tells the controller how the network should

behave- The application turns the switch into a load balancer, firewall,

router or something else

• Why don’t we have OpenFlow on Access Points?- There is an OpenWRT flavor that turns the AP into a Open vSwitch

• Current OpenFlow WLAN support- We may see some functions in version 1.6- Probably developed by external partners

• APs are limited in resources- CPU- Memory- OpenFlow could cause performance issues

• Availabilty of CAM/TCAM - An AP can not replace a dedicated campus firewall- Performance issues (again)

So…does SDN equal OpenFlow?• No

- Really...No.- There is no OpenFlow in the definition of what SDN is- There are also several broader definitions of SDN

• Broker SDN- Keeps the existing control plane- Exposes northbound APIs

• Overlay SDN- SDN is deployed as an overlay- Existing network remains untouched

• Other approaches- BGP-LS- PCEP- NETCONF/YANG

SDN

• We could have OpenFlow support on a WLAN controller• Adds delay to control actions• Only suitable for centralised data forwarding• Controllers are often not even on site

SDN Controller Existing Control Plane

OpenFlow+Delay

+Delay

SDN enables “network service factories”• Applications, hardware and device operating system may no longer be

developed by the same company• Services can be delivered faster• Services can be developed independently of the physical network

infrastructure• Vertical integration can drive down costs

Limited benefits• WLAN management tools already provide centralised management

and policy control• WLAN security policies are pretty static – they do not change over

time, they change based on the user profile• Most companies choose a single WLAN vendor

Limited WLAN vendor participation in SDN initiatives• OpenFlow• ONF • OpenDaylight

WLAN vendors already address most of these.

Roaming Optimisation• How to provide the optimal network path after roaming? • Roaming between different radio technologies

Application QoS Optimisation• Bandwidth on demand across the whole infrastructure

Radio Resource Management*• The vendor provided RRM doesn’t suit me• I want my own interference management• I want to apply machine learning algorithms…

Today

SDN

QoS will only work if already configured end-to-end

SDN Controller

Bandwitdhrequest

Media Server

Media Server

Adjust flow policy

Today

SDN

Non-optimal traffic path!

L3 Boundary

SDN Controller

Roaming notification

Adjust traffic flows

L3 Boundary

• A generic RRM algorithm can rarely handle all RF environments

• RRM algorithms require manual fine tuning

• Research shows even overlapping channel schemes sometimes work- Ester Mengual, Eduard Garcia-Villegas, Rafael Vidal, Channel management in a campus-wide

WLAN with partially overlapping channels“.

• Simultaneous use of different access technologies- WLAN, LTE, UMTS, Ethernet…- Load balancing- Aggregation

§ Software defined radio- OFDM carrier selection

• It is probably not worth replacing WLAN control plane- Supposing the control plane does its job

• Broker SDN seems like the most viable option- Exposing northbound APIs makes more sense than OpenFlow- Even some hybrid solutions leveraging management protocols will be

labeled SDN – that is OK- SDN will become important in terms of network automation and

orchestration across different technologies

• There may be niche cases outside the Enterprise market- Mobile Network Operators and Service Providers

What is it really about?Software defined networking or programmability?

Marko Tišler

CWNE #126

@tishlaaar