Obs final-english version

Dept. of EE, Tsinghua Univ.Laboratory of Broadband optical network

Tel: 86-10-62773197 [email protected]

OBSNetwork principles& key technologies

Shaozhong ZhengDept. of Electronic Engineering, Tsinghua Univ.

2010-10-18

1. Background

2.Principles

3.Key technologies

4.News

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Outline

1. Background

2.Principles

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3.Key technologies

4.News

Outline

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OFC 2005UC DavisOptical Label Switching Network testbed2.5Gb/smulticast and unicast video streaming

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OBS

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OPS

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OPS

OPS

Optical

Packet

Switch

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Why we need OPS?

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OutlineIP RouterPeer Routing

ATM SwtichPVC Mesh

SONETADM Ring

DWDMPoint-point

A typical data network 4-layer

Using Telecomm. Network

Shortcomings :1、complicated, bad flexibility2、 bandwidth bottlenecks3、 High energy consumption

Background

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OutlinePower Consumption in Routers

Background

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OutlinePower Consumption in Routers

Through-put1.2Tbps

PowerConsumption

15kw

92Tbps>1Mw

Google Data Center>100Mw

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TimeWDM

SONET

ATM

IP/MPLS

WDM

SONET

IP/MPLS

WDM

IP/MPLS

Flat network architectureIP over WDM

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High-capacity Optical NetworkingPacket-levelFlexibility

Optical amplifiers

Point-to-pointWDM &DWDM

DWDMpoint-to-multipoint

Static

Dynamic OADMse-g- STM1 on demand

Colored section rings

OXC and DXC co-existence

Wavelengthconversion

Wavelengthrouting

OpticalPacket

Switching

1994 2000 2007 Time

Net

wor

k Fu

nctio

n

Representative : SDHOptical technologies only Used for transport

Another Trend…ASON

Added complex electroniccontrol layer

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High-capacity Optical NetworkingPacket-levelFlexibility

Optical amplifiers

Point-to-pointWDM &DWDM

DWDMpoint-to-multipoint

Static

Dynamic OADMse-g- STM1 on demand

Colored section rings

OXC and DXC co-existence

Wavelengthconversion

Wavelengthrouting

OpticalPacket

Switching

1994 2000 2007 Time

Net

wor

k Fu

nctio

n

Representative : SDHOptical technologies only Used for transport

Another Trend…ASON

Added complex electroniccontrol layer

OPSAll-Optical Routing

Optical PacketFlexible & Efficient

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Optical

Packet

Switch

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Optical

Burst

Switch

Challenge:High-speed Optical switchOptical RAM

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Solution:Packet-aggregatingSeparation ofData& Control signals

Optical

Burst

Switch

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Control Unit

Control Unit

OPSSwitch Speed: n s

OBSSwitch Speed: m s

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Control Unit

Control Unit

OPSSwitch Speed: n s

OBSSwitch Speed: m s

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Proponent of OBS, S. J. B. Yoo:Optical burst switching (OBS) is implemented

either as a fast reconfiguring optical circuit switching (OCS) or as OPS with large aggregated packets.

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1. Background

2.Principles

3.Key technologies

4.News

Outline

1010101

1010101

Core Node Edge Node Optical Burst

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Principle

Control : Burst head

Transport: Burst

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Principle

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FDL Buffer

demux Switch

Matrix

MUX

Burst ReceiverBurst Transmitter

Burst Assembly/Disassembly Unit

Framing Defaming

Optical Label

process

ElectronicBuffer

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Principle

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Outline

1. Background

2.Principles

3.Key technologies

4.News

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PrincipleTechnologies

QoS TechnologiesKey Technologies

Switching

Contention Resolution

Signaling &Resource Reservation

Scheduling

Burst Assembly

1. Burst AssemblyThe procedure of aggregating packets from various sources into bursts.Burst Assembly/Disassembly.

Timer-basedBurstlength-based

Mixed timer/burstlength-based

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1. Burst Assembly

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Burst Assembly Unit

Assemblyalgorithms

Packets to the same

destination

Class 1……Class n

Arriving Data streams

……

Switch Unit

………………

Principlesof Edge Nodes

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1.1. Timer-based

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IP IPGbE

IPGbEATM

IPGbEATM

IPGbEATMSONET

Other

Time

T

Burst Length

IPGbEATMSONET

Other

Advantages: guarantee on the assembly delayDisadvantages: No guarantee on the burst length

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IP IPGbE

IPGbEATM

IPGbEATM

SONETOther1

Time

Burst Length

IPGbEATM

SONET

IPGbEATM

SONETOther1

Other2

IPGbEATM

SONETOther1

Other2

L

1.2. Burstlength-basedOutlineBackground


Advantages: guarantee on the burst lengthDisadvantages: No guarantee on the assembly delay

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IP IPGbE

IPGbEATM

IPGbEATM

SONETOther1

Time

Burst Length

IPGbEATM

SONET

IPGbEATM

SONETOther1L

T

1.3. Mixed timer/burstlength-based

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IP IPGbE

IPGbEATM

IPGbEATM

SONETOther1

Time

Burst Length

IPGbEATM

SONET

IPGbEATM

SONETOther1L

T

Address the deficiency associatedwith the assembly algorithms

mentioned above

1.3. Mixed timer/burstlength-based

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1.4. Impact of burst lengthOutlineBackground


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Generally, the average length of burst is

40Kbyte,approximately

1.4. Impact of burst lengthOutlineBackground


2. Signaling &Resource Reservation

Generation and transmission of a burst header packet to reserve network resourcesand to configure switches

JET protocolJIT protocol

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2.1. SignalingGeneration and transmissionof a burst header packet

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Destination NodeBurst length

……

TAW approachTAG approach

offset-based approach

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2.1. Signaling - TAWTAW : Tell and wait

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Time

TimeSource

Destination

Burst Head Acknowledgement Burst

Low efficiency T

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2.1. Signaling - TAWTAW : Tell and wait

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Time

TimeSource

Destination

Burst Head Acknowledgement Burst

Low efficiency T

Advantage: Low Burst-loss rateDisadvantage: High delay, low

bandwidth-efficient

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2.1. Signaling - TAGTAG：Tell and go

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Time

TimeSource

Destination

Buffer the Burst

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Burst Head Burst

2.1. Signaling - TAGTAG：Tell and go

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Time

TimeSource

Destination

Buffer the Burst

Advantage: Low DelayDisadvantage: No guarantee on reservation,

Optical buffer

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Burst Head Burst

2.1. Signaling - OffsetThe header and burst are separatedby an offset time.

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Time

TimeSource

Destination

Offset time T

During the offset time, intermediate nodes process the header and configure the switch prior to the burst’s arrival.

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Burst Head Burst

2.1. Signaling - OffsetThe header and burst are separatedby an offset time.

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Time

TimeSource

Destination

Offset time T

During the offset time, intermediate nodes process the header and configure the switch prior to the burst’s arrival.

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Burst Head Burst

A balanceHard to determine an perfect offset time

TAW approach

•The Burst is sent only after resource reservation is successful.

•AdvantageLow burst-loss rate

•DisadvantageHigh network delay; Low efficiency.

TAG approach

•The Burst and the head are sent together.

•AdvantageLow delay; Simple;

•DisadvantageLow delay; Simple;

Offset-time

•The Burst and the head is separated by an offset time.

•A balance between network delay and the burst-loss rate.

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Delayed reservation: reserves the resourcesstarting from the point in time at which the burstis expected to arrive at the node.Immediate reservation: reserves the resourcesimmediately after the burst header is processed.

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2.2. ReservationThe reservation technique determinesthe starting time of the reservation and determines how and when the reservation should be released.

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Reservation ProtocolJET Protocol & JIT Protocol

JET = Time-offset + Delay ReservationJust Enough TimeJIT = TAG + Immediate reservationJust In Time

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3. SchedulingA scheduler chooses a proper wavelength taking into consideration the existing reservations and make a new reservation on this selected channel.

LAUCMin-SVMin-EVBest-Fit

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C1

C2

C3

C4

C5

s1 t1

s2 t2

s3

s4 t4

s5 t5Time

LAUC: latest available unscheduled channel New Burst

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C1

C2

C3

C4

C5

Time47

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LAUC: latest available unscheduled channel

C1

C2

C3

C4

C5

Time48

Advantages: simpleDisadvantage: Low bandwidth efficiencyMake use of the voids among bursts

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LAUC: latest available unscheduled channel

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C1

C2

C3

C4

C5

s1 t1

s2 t2

s3

s4 t4

s5 t5Time

LAUC –VF:带空隙填充的LAUCNew Burst

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C1

C2

C3

C4

C5

s1 t1

s2 t2

s3

s4 t4

s5 t5Time

LAUC –VF:带空隙填充的LAUCNew Burst

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Optimized using computer graphicsO(WlogM) -> O(logM)

C1

C2

C3

C4

C5

s1 t1

s2 t2

s3

s4 t4

s5 t5Time

Min-SVA faster LAUC-VF

New Burst

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C1

C2

C3

C4

C5

s1 t1

s2 t2

s3

s4 t4

s5 t5

Min-EVNew Burst

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Time

C1

C2

C3

C4

C5

s1 t1

s2 t2

s3

s4 t4

s5 t5

Best-FitNew Burst

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Time

C1

C2

C3

C4

C5

LAUC-VF/Min-SV

LAUC/Horizon

Min-EV

Best-Fit

s1 t1

s2 t2

s3

s4 t4

s5 t5

New Burst

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Time

Algorithms Time complexity Bandwidth Utilization

LAUC O(W) Low

LAUC-VF O(WlogM) High

Min-SV/EV O(logM) High

Best-Fit O(log2M) High

Comparison

W: Number of wavelengths at each output port M: Maximum number of data bursts (or reservations) on all channels

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4. ContentionResolutionOwing to the one-way reservation mechanism, bursts that contend for the same resources mayend up being lost.

Node level: conflict resolutionSystem level: reduce the conflict

Network level: avoid conflict56

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4.1. conflict resolution

Optical bufferStore and ForwardA challenge to develop an mature Optical RAM

Wavelength conversionMulti-wavelength resolutionMuch lower burst lossImmature and expensive technology

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4.1. Contention Resolution

Deflection Routingdiverts bursts to alternate available output ports when contention occursOut of order arrivals;Possible instability;Optical buffers needed.

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4.2. Reduce conflict

Slotted OBS networkSynchronizing network;Mechanisms to provide synchronizationat each node;fixed-length bursts

Contention controlAttempt to prevent contention

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4.4.Avoid Conflict

Zero-burst-loss OBSBuffer the data in edge nodesNetwork structure: Ring and Star

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5. QoS TechnologyQoS mechanisms typically provide differentiation with respect to data loss or delay.

Assembly processSignaling Mechanism

Scheduling algorithmsContention resolution

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QoS Technology

Assembly processChanging the assembly thresholds will affect the delay experienced by packets, allowing for delaydifferentiation.Resource ReservationLonger interval between head and burst, lower burst-loss rate

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QoS Technology

Scheduling algorithmsPreemption mechanisms allow high-priority bursts to preempt already scheduled low-priority bursts;Early drop mechanisms prevent the scheduling of low-priority bursts;Wavelength allocation schemes restrict the number of wave-length channels that can be used for bursts of a given priority.

Contention ResolutionDrop the low-priority bursts

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6. SwitchingA critical component in OBS is the optical switch fabric.

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Space SwitchingWavelength conversion

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6.1. Switching-SpaceUsing the Optical Switch Matrixto exchange optical bursts.

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Input

Output

OpticalSwitchMatrix

MEMsSOA

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6.1. Switching-MEMsMatrixes consist of numbers oftiny lenses.

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MEMs： microelectromechanical systems

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6.1. Switching-MEMsMatrixes consist of numbers oftiny lenses.

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MEMs： microelectromechanical systems

Advantages: Mature IC technologies; Disadvantages: Slow switching speed, 1~10ms

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6.1. Switching-SOA

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SOA： semiconductor optical amplifier

SOAInput Optical power

Output Optical power

Injection current

High-speed Optical swtich

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6.2. Switching-AWGUsing wavelength technologies to exchange optical bursts.

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n non-coupled linear array of waveguides

Star coupler

inputl1 .... lN

outputl1 .... lN

Star coupler

AWG: Arrayed Waveguide Grating

Principle: Using star coupler and AWG to separate differentwavelengths into different outputs.

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6.2. Switching-AWGUsing wavelength technologies to exchange optical bursts.

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AWG + Wavelength conversion = Wavelength Switching

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OtherTCP over OBSOBS multicastOBS grid calculation……

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1. Background

2.Principles

3.Key technologies

4.News

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Outline

NewsKey elementsNew network structuresImportant test beds around the world

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News

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Key elements- Optical integration

2010, Larry A. Coldren (UCSB university, USA) has demonstrated an 8x8 InP-based monolithic tunable optical router capable of 40 Gbps operation per port.

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News

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Integrated Optical switchesThe COBRA Research Institute, Eindhoven University of Technology, Netherlands, developed an integrated SOA-based optical switches.

Integrate 4 SOA optical switches;160Gbit/s;

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News

Key elements- Optical integration

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Optical RAM，K. Kitayama， ACP 2009

Developed optical Flip-Flops based on optical Bistability using high-Q photonic crystal nano-cavity.Transform energy: 30 fJ/bitMinimum optical bias power: 40μWStorage time 150 ns (Under the bias power 250 μW)

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News

Key elements- Optical buffer

Thank you!

Shaozhong ZhengDept. of Electronic Engineering, Tsinghua Univ.

2010-10-18

Dept. of EE, Tsinghua Univ.Laboratory of Broadband optical network

Tel: 86-10-62773197 [email protected]

Education

Obs final-english version