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Software Defined Networking


So#ware-Defined Networking (SDN) refers to a newapproach for network programmability, that is, thecapacity to ini?alize, control, change, and managenetwork behavior dynamically via open interfaces.[RFC7426]


So#ware-Defined Networking (SDN) refers to a newapproach for network programmability, that is, thecapacity to ini?alize, control, change, and managenetwork behavior dynamically via open interfaces.[RFC7426]

Adifferentwayofthinkingaboutnetworks

X


SpecializedPacketForwardingHardware

STP ICMP OSPF

OperaCngsystem

Typical network node 6



App App App


App App App


App

App

App


App App App


OperaCngSystem

OperaCngSystem

OperaCngSystem

OperaCngSystem

OperaCngSystem

App App App

Typical network 7

AllnodesareequalPeer-to-peerprotocls


Protocolli peer-to-peer

Peer-to-peer are excellent: •  They can be easily extended •  robust •  scalable (think about the Internet!)

But… •  They are quite “expensive” to run •  problems are difficult to localize •  very very difficult to update and innovate

Software Defined Networking 9

SeparateDataPlanefromControlPlane


App App App SpecializedPacketForwardingHardware

App

App

App


App App App


OperaCngSystem

OperaCngSystem

OperaCngSystem

OperaCngSystem

App App App

ControlPlane

DataPlaneSpecializedPacket

ForwardingHardware

App App App

OperaCngSystem

Basic idea of SDN 9


SDN moves network functionalities in a Network Operating System 10


App App App


App App App


App App App


App App App


OperaCngSystem

OperaCngSystem

OperaCngSystem

OperaCngSystem

OperaCngSystem

App App App




App App App


App App App


App App App


App App App


App App App

NetworkOperaCngSystem








NetworkOperaCngSystem

App App App


App

Switch

Switch

Switch

App App

SwitchSwitch

Controller

Northboundinterface

Southboundinterface

SDN stack: 3 layers, 2 interfaces 13

Deviceslayer

Networkservicelayer

ApplicaConlayer


Software di controllo

Router

Forwarding Hardware



Router

Forwarding Hardware

Authentication, Securit

y, Access Control

HELLO

IPV6 multicast Mobile IP

L2 VPN VLAN OSPF-TE

RSVP-TE HELLO HELLO

Firewall

IPSec



Router

Forwarding Hardware

Authentication, Securit

y, Access Control

HELLO

IPV6 multicast Mobile IP

L2 VPN VLAN OSPF-TE

RSVP-TE HELLO HELLO

Firewall

IPSec

InfrastructurenodesdomanythingsOSPF,BGP,mul?cast,differen?atedservices,TrafficEngineering,NAT,firewalls,MPLS,redundantlayers,…

TheyshoulddolessthingsWELL!


Number of published RFCs


Protocols implemented in a generic switch


Windows(OS)Windows(OS)

Linux MacOS

x86(Computer)

Windows(OS)

AppApp

LinuxLinuxMacOSMacOS

VirtualizaConlayer

App

Controller1

AppApp

Controller2

VirtualizaConor“Slicing”

App

OpenFlow

Controller1ONOS(NetworkOS)

Controller2NetworkOS

Technological Trend

ComputerIndustry NetworkIndustry

Hardwaresublayersimpleandstable,programmability,isolaConandcompeCConinupperlayers


Abstractions

Abstractions allow programs easier to write and maintain Data plane abstractions: •  the OSI stack Control plane abstractions? They must be developed: •  Devices layer •  Network services layer


Devices Abstraction

Currentdevices

RouterIP

SwitchEthernet

Firewall

NATbox

L4switch

Abstractdevice

Flowtable

TheFlowTableabstracConisindependentofthelayerinwhichthedevicewilloperateAflowisdefinedbyapacketclassificaConrule,basedontheheadervalues


Flow table abstraction


Astrazione a tabella di flussi 25

Rule AcCon Stats

Rule AcCon Stats

Rule AcCon Stats

Rule AcCon Stats

highestpriority

lowestpriority

Ognipacche\ovieneclassificatoinbaseaunaregola

DefaultRule

AcCon:SendtoController Stats


Flow table abstraction 26

SwitchPort

MACsrc

MACdst

Ethtype

VLANID

IPSrc

IPDst

IPProt

L4sport

L4dport

Rule AcCon Stats

1.  Forwardpackettozeroormoreports2.  Encapsulateandforwardtocontroller3.  Sendtonormalprocessingpipeline4.  ModifyFields5.  Anyextensionsyouadd!

Matchescanbeexactorwithawildcard

Packet+bytecounters

VLANpcp

IPToS

…


One table, many possible behaviors 27

Name Port MACSrc

MACDst

EthType

VLANID

IPSrc IPDst IPProt UDP/TCPSport

UDP/TCPDport

AcLon

Switchboard p1 * * * * * * * * * port2

PortMirroring p1 * * * * * * * * * port2,port3

L2Switching * * 00:1f... * * * * * * * port2

VLANSwitching * * 00:1f… * vlan3 * * * * * port2

IPRouCng * * * * * 5.6.7.8/16

* * * writeMAC,port2

Firewall * * * * * * * * * 22 drop

FlowSwitching p3 00:20... 00:1f... 0800 vlan3 1.2.3.4 5.6.7.8 4 17264 80 port2


Controller

PC

HardwareLayer

SoiwareLayer

FlowTable

MACsrc

MACdst

IPSrc

IPDst

TCPsport

TCPdport AcCon

OpenFlowAgent

port4port3port2port1

Reactive installation of Rules 28

✗Packet1only

1.2.3.45.6.7.8


Controller

PC

HardwareLayer

SoiwareLayer

FlowTable

MACsrc

MACdst

IPSrc

IPDst

TCPsport

TCPdport AcCon

OpenFlowAgent



✗Packet1only

1.2.3.45.6.7.8


Controller

PC

HardwareLayer

SoiwareLayer

FlowTable

MACsrc

MACdst

IPSrc

IPDst

TCPsport

TCPdport AcCon

OpenFlowAgent

80123455.6.7.81.2.3.456:7812:34 port1



✗Packet1only

1.2.3.45.6.7.8


Controller

PC

HardwareLayer

SoiwareLayer

FlowTable

MACsrc

MACdst

IPSrc

IPDst

TCPsport

TCPdport AcCon

OpenFlowAgent

80123455.6.7.81.2.3.456:7812:34 port1



✗ ✓Packet1only

Packets2ton

1.2.3.45.6.7.8


Controller

PC

HardwareLayer

SoiwareLayer

FlowTable

MACsrc

MACdst

IPSrc

IPDst

TCPsport

TCPdport AcCon

OpenFlowAgent


Proactive installation of Rules 32

1.2.3.45.6.7.8


Controller

PC

HardwareLayer

SoiwareLayer

FlowTable

MACsrc

MACdst

IPSrc

IPDst

TCPsport

TCPdport AcCon

OpenFlowAgent

**5.6.7.8*** port1


Proactive installation of Rules 33

Everypacket1.2.3.45.6.7.8


Abstraction of Network Services

CurrentServices

Topologydiscovery

PathcomputaCon

StatedisseminaCon

Faultrecovery

AbstractServices

NetworkMap

Intent-basedNetworking


Flowtable

NetworkMap

L4L3L2.5L2L1

TablesforidenLfiersandacLons

FlowsarecombinaLonof

NorthboundAPI

NetworkApplicaLonsrouLng,access-control,mobility,traffic-engineering,guarantees,recovery,bandwidth-on-demand…

SouthboundAPI

ControlPlane

StateCollecLonStateDisseminaLon&ApplicaLonIsolaLon

BuiltforPerformanceScale&Reliability

SDN Abstractions


Example of network application Classic imperative approach

Objective: establish a connection between Host 1 and Host 2

Host1 Host2



Objective: establish a connection between Host 1 and Host 2 1.  Discover network topology

Host2Host1



Objective: establish a connection between Host 1 and Host 2 1.  Discover network topology 2.  Determine the path

Host2Host1



Objective: establish a connection between Host 1 and Host 2 1.  Discover network topology 2.  Determine the path 3.  Write the rules that define the flows and corresponding actions

Host1 Host2



Objective: establish a connection between Host 1 and Host 2 1.  Discover network topology 2.  Determine the path 3.  Write the rules that define the flows and corresponding actions 4.  Install rules on devices

Host1 Host2


Example of network application Problems

This approach may fail in several ways

Host1 Host2



This approach may fail in several ways Missing rules, refused or cancelled •  Continuosly control that devices can be reached •  Guarantee that a consistent state is reached between two updates

Host1 Host2



This approach may fail in several ways Missing rules, refused or cancelled •  Continuously control that devices can be reached •  Guarantee that a consistent state is reached between two updates Topology Modifications •  Listen to failure events from all devices and links •  Compute new paths and new flows

Host1 Host2


Programming Network Applications

Each application requires the calculation of routing paths, the installation of rules, the updating of state machines

In the event of failures, we risk inconsistent behavior Bugs need to be fixed at various points in the network Updating algorithms involving multiple applications is expensive Difficult to resolve conflicts between applications


Programming Network Applications Declarative Programming (intent-based networking)

Network intentions are a high-level interface that describes which result you want to achieve and delegates how to get it to the network services layer

It hides the complexity of the network from applications It guarantees the maintenance of the result even in the presence of

topology changes


Intent Example

Host to Host Intent


Intent Example

Host to Host Intent

IntentServiceAPI

submit()


Intent Example

COMPILATION

Path Intent

Path Intent

Host to Host Intent


Intent Example

COMPILATION

INSTALLATION

Flow Rule Batch

Flow Rule Batch Flow Rule Batch

Flow Rule Batch

Path Intent

Path Intent

Host to Host Intent


SDN in action


Google’s B4 Architecture

SiteA

DataCenter

OFASwitch

OFASwitch

OFASwitch

OFASwitch

DataCenter

SiteB

DataCenter

SiteC

B4WAN

Servers

RAPTE-AGENTOFC

paxosQuaggaQuaggaQuagga Paxos SiteBControllers

Servers

SiteCControllers

Servers

Switchhardware

iBGP

eBGP

Sitecontrollers

GatewayGatewayCentralTEServersCentralTEServers

GlobalTE

software defined networking › martignon › documenti › rim › sdn_eng.pdf · software defined...

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