Download ppt - Shivkumar Kalyanaraman Rensselaer Polytechnic Institute 1 IP over SONET and Optical Networks Shivkumar Kalyanaraman Rensselaer Polytechnic Institute

Shivkumar KalyanaramanRensselaer Polytechnic Institute

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IP over SONET and Optical Networks


[email protected] http://www.ecse.rpi.edu/Homepages/shivkuma

Based in part on slides of Nick McKeown (Stanford)

http://www.ecse.rpi.edu/Homepages/shivkuma


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Internet Core Transport Evolution & Trends SONET Optical Networking: Components Control plane:

Overlay model, peer model Issues: provisioning, restoration, routing, traffic

engineering

Overview


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Telephony: Multiplexing

Telephone Trunks between central offices carry hundreds of conversations: Can’t run thick bundles!

Send many calls on the same wire: multiplexing Analog multiplexing

bandlimit call to 3.4 KHz and frequency shift onto higher bandwidth trunk

Digital multiplexing: convert voice to samples 8000 samples/sec => call = 64 Kbps


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Telephony: Multiplexing Hierarchy Pre-SONET:

Telephone call: 64 kbps T1 line: 1.544 Mbps = 24 calls (aka DS1) T3 line: 45 Mbps = 28 T1 lines (aka DS3)

Multiplexing and de-multiplexing based upon strict timing (synchronous) At higher rates, jitter is a problem Have to resort to bit-stuffing and complex

extraction => costly “plesiochronous” hierarchy SONET developed for higher multiplexing aggregates

Use of “pointers” like C to avoid bit-stuffing


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Digital Telephony in 1984

Key System Aspects:Key System Aspects:• M13 Building BlocksM13 Building Blocks• AsynchronousAsynchronous OperationOperation• Electrical DS3 SignalsElectrical DS3 Signals• Proprietary Fiber Proprietary Fiber Systems Systems • Brute ForceBrute Force Cross Cross ConnectConnect• AT&T Network/Western AT&T Network/Western Electric EquipmentElectric Equipment

CentralCentralOfficeOfficeCentralCentral

OfficeOffice

CentralCentralOfficeOffice

FiberFiber

Fiber OpticFiber OpticTransmissionTransmission

SystemsSystems• SwitchesSwitches• Leased LineLeased Line

M13M13 M13M13

DS3DS3

DS1DS1

DS3DS3

DS1 CrossDS1 CrossConnectConnect

M13M13

DS1DS1

DS1DS1

No GuaranteedNo GuaranteedTimingTiming

SynchronizationSynchronization


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Post-AT&T Divestiture Dilemmas

Needs:Needs: • Support Faster Fiber Support Faster Fiber • Support New ServicesSupport New Services• Allow Other Allow Other TopologiesTopologies• Standardize Standardize RedundancyRedundancy• Common OAM&PCommon OAM&P• Scalable Cross Scalable Cross ConnectConnect

DifferentDifferentCarriers,Carriers,VendorsVendors

• SwitchesSwitches• Leased LineLeased Line• LAN ServicesLAN Services• Data ServicesData Services M13M13

SupportSupportOtherOther

Topologies,Topologies,Protect FibersProtect Fibers

DS1DS1

InternalInternalDS3 CrossDS3 CrossConnectConnect


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SONET Synchronous Optical Network Layer 1 Standards For Communication over Fiber

Optic (and Electrical) Links Facilitates:

Fiber Optic Link Speed Increases Variety Of Topologies and Grooming Functions Operations, Administration, Maintenance, and

Provisioning (OAM&P) Used As Telephony Carrier Equipment And CPE

Interconnect


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Equipment Types

PTEPTE

SONET EndSONET EndDevice - I.e.Device - I.e.TelephonyTelephonySwitch, RouterSwitch, Router

• Section Termination Section Termination (STE)(STE)

SectionsSections

RepeatersRepeaters

PTEPTE

LineLine• Line Termination (LTE)Line Termination (LTE)

PathPath

• Path Termination (PTE)Path Termination (PTE)


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STS-1 Frame Format90 Bytes90 Bytes

Or “Columns”Or “Columns”

99RowsRows

Small Rectangle =1 Byte

Frame TransmissionFrame Transmission• Top Row First, Sent Left To Top Row First, Sent Left To RightRight• 125 125 s/Frames/Frame• 810 Bytes/Frame810 Bytes/Frame• 51.84 Mbps Rate51.84 Mbps Rate• Frame Contains One PayloadFrame Contains One Payload

STS = Synchronous Transport Signal


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STS-1 Headers

90 Bytes90 BytesOr “Columns”Or “Columns”

99RowsRows

Section Overhead (SOH)

Line Overhead (LOH)Path Overhead (POH)


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Headers: Section Overhead (SOH)

A1=0xF6

A2A2=0x28=0x28

J0/Z0J0/Z0STS-IDSTS-ID

B1B1BIP-8BIP-8

E1E1OrderwireOrderwire

F1F1UserUser

D1D1Data ComData Com



Section OverheadSection Overhead• 9 Bytes Total9 Bytes Total• Originated And Terminated Originated And Terminated By All By All Section Devices (Regenerators, Multiplexers, (Regenerators, Multiplexers, CPE)CPE)• Other Fields Pass UnaffectedOther Fields Pass Unaffected

RcvRcvSOHSOH

Selected Fields: •A1,A2 - Framing Bytes•BIP-8 - Bit Interleaved Parity• F1 User - Proprietary Management

XmtXmtSOHSOH


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Headers: Line Overhead (LOH)H1H1

PointerPointerH2H2

PointerPointerH3H3

Pointer ActPointer ActB2B2

BIP-8BIP-8K1K1

APSAPSK2K2

APSAPSD4D4

Data ComData ComD5D5

Data ComData ComD6D6

Data ComData Com

Line OverheadLine Overhead• 18 Bytes Total18 Bytes Total• Originated And Terminated Originated And Terminated By All Line Devices By All Line Devices (Multiplexers, CPE)(Multiplexers, CPE)• LOH+SOH=TOH (LOH+SOH=TOH (Transport Transport OHOH))

Selected Fields: •H1-3 - Payload Pointers•K1, K2 - Automatic Protection Switching• D4-D12 - 576 kbps OSI/CMIP







S1S1SyncSync

M0M0REIREI

E1E1OrderwireOrderwire

RcvRcvSOHSOH

XmtXmtSOHSOHXmXm

ttSOSOHH

XmXmtt

LOLOHH RcvRcv

SOHSOH

RcvRcvLOHLOH


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Headers: Path Overhead (POH)J1J1

TraceTraceB3B3

BIP-8BIP-8C2C2

Sig LabelSig Label

Path OverheadPath Overhead• H1,H2 fields of LOHH1,H2 fields of LOH points to points to Beginning of POHBeginning of POH

Selected fields:•BIP-8 - Parity• C2 - Payload Type Indicator• G1 - End End Path Status

G1G1Path StatPath Stat

F2F2UserUserH4H4

IndicatorIndicator

PTEPTE

Z3Z3GrowthGrowth

Z4Z4GrowthGrowth

Z5Z5TandemTandem

PTEPTESTESTE

Frame NFrame NFrame N+1Frame N+1

Frame NFrame NFrame N+1Frame N+1

•POH Beginning POH Beginning FloatsFloats Within Within FrameFrame• 9 Bytes (1 Column) 9 Bytes (1 Column) SpansSpans FramesFrames• Originated And Terminated By Originated And Terminated By All Path Devices (I.e. CPE, All Path Devices (I.e. CPE, Switches)Switches)• STE Can Relocate PayloadSTE Can Relocate Payload


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SPE

Synchronous Payload EnvelopeSynchronous Payload Envelope• Contains POH + DataContains POH + Data• First Byte Follows First Byte Of First Byte Follows First Byte Of POHPOH• Wraps In Subsequent ColumnsWraps In Subsequent Columns• May Span FramesMay Span Frames• Up To 49.536 Mbps for Data:Up To 49.536 Mbps for Data:

•Enough for DS3Enough for DS3

Defined Payloads• Virtual Tributaries (For DS1, DS2)• DS3• SMDS• ATM• PPP …


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Accommodating JitterPositive Stuff Positive Stuff Negative Stuff Negative Stuff

• To Shorten/LengthenTo Shorten/Lengthen Frame: Frame:• Byte After H3 Ignored; Or H3 Holds Extra Byte Byte After H3 Ignored; Or H3 Holds Extra Byte

• H1, H2 Values Indicate Changes - Maximum Every 4 H1, H2 Values Indicate Changes - Maximum Every 4 FramesFrames• Requires Requires CloseClose (Not Exact) (Not Exact) Clock SynchClock Synch Among Among ElementsElements


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STS-N Frame Format

Composite Frames:Composite Frames:• Byte InterleavedByte Interleaved STS-1’s STS-1’s• Clock RateClock Rate = Nx51.84 Mbps = Nx51.84 Mbps

90xN Bytes90xN BytesOr “Columns”Or “Columns”

N Individual STS-1 FramesN Individual STS-1 Frames

ExamplesExamples STS-1STS-1 51.84 Mbps 51.84 Mbps

STS-3STS-3 155.520 Mbps 155.520 MbpsSTS-12STS-12 622.080 Mbps 622.080 MbpsSTS-48STS-48 2.48832 Gbps 2.48832 GbpsSTS-192 9.95323 GbpsSTS-192 9.95323 Gbps

Complex demultiplexing !!


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STS-Nc Frame Format

Concatenated mode:Concatenated mode:• Same TOH Structure And Data Rates As Same TOH Structure And Data Rates As STS-NSTS-N• Not All TOH Bytes UsedNot All TOH Bytes Used• First H1, H2 Point To POHFirst H1, H2 Point To POH• Single PayloadSingle Payload In Rest Of SPE In Rest Of SPE• Accommodates FDDI, E4, dataAccommodates FDDI, E4, data

90xN Bytes90xN BytesOr “Columns”Or “Columns”

Transport Overhead: Transport Overhead: SOH+LOHSOH+LOH

Current IP over SONET technologies use concatenated mode: OC-3c (155 Mbps) to OC-192c (10 Gbps) rates


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SONET Network Elements

Nonstandard, Functional Nonstandard, Functional NamesNamesTM:TM: Terminal Mux Terminal MuxADM:ADM: Add-Drop Mux Add-Drop MuxDCC:DCC: Digital Cross Connect Digital Cross Connect (Wideband and (Wideband and Broadband)Broadband)MN:MN: Matched Node Matched NodeD+R:D+R: Drop and Repeat Drop and Repeat

ADMADMTMTMDS1sDS1s

DS1sDS1s

MNMN MNMN

MNMNDCCDCC

D+RD+R

D+RD+R

D+RD+RMNMN


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Topologies

DCCDCC

ADMADM

ADMADM

ADMADM

DCCDCC

ADMADM

ADMADM

ADMADM 2 Fiber Ring2 Fiber RingEach Line IsEach Line IsFull DuplexFull Duplex

DCCDCC

ADMADM

ADMADM

ADMADM 4 Fiber Ring4 Fiber RingEach Line IsEach Line IsFull DuplexFull Duplex

DCCDCC

ADMADM

ADMADM

ADMADM

Uni- vs. Bi-Uni- vs. Bi-DirectionalDirectionalAll Traffic Runs All Traffic Runs Clockwise, vs Either Clockwise, vs Either WayWay


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Automatic Protection Switching (APS)

ADMADM

Line Protection SwitchingLine Protection SwitchingUses Uses TOHTOHTrunk ApplicationTrunk ApplicationBackup Capacity Is IdleBackup Capacity Is IdleSupports 1:n, where n=1-14Supports 1:n, where n=1-14

Automatic Protection SwitchingAutomatic Protection Switching• Line Or Path BasedLine Or Path Based• Revertive vs. Non-RevertiveRevertive vs. Non-Revertive• Restoration Times ~ Restoration Times ~ 50 ms50 ms• K1, K2 Bytes Signal ChangeK1, K2 Bytes Signal Change

ADMADMADMADM ADMADM

Path Protection SwitchingPath Protection SwitchingUses Uses POHPOHAccess Line ApplicationsAccess Line ApplicationsDuplicate Traffic Sent On ProtectDuplicate Traffic Sent On Protect1+11+1

ADMADMADMADM


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Protection Topologies - Linear Two nodes connected to each other with two or

more sets of links

Working Protect Working Protect

(1+1) (1:n)


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Two or more nodes connected to each other with a ring of linksLine vs. Drop interfacesEast vs. West interfaces

Protection Topologies - Ring

E

W

W

E

W

EW

E

D

LL

Working Protect


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Protection Topologies - Mesh Three or more nodes connected to each other

Can be sparse or complete meshesSpans may be individually protected with

linear protectionOverall edge-to-edge connectivity is protected

through multiple paths

Working

Protect


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Packet Over SONET (POS)

PPPPPP ByteByteStuffStuffFCSFCS ScramblingScrambling SONETSONET

FramingFraming

Standard PPP Encapsulation• Magic Number Recommended• No Address and Control Compression• No Protocol Field Compression

Standard CRC Computation• OC3 May Use CRC-16• Other Speeds Use CRC-32

Special Data Scrambler• 1+ x43 Polynomial• Protects Against Transmitted Frames Containing Synch Bytes Or Insufficient Ones Density

SONET Framing• OC3, OC12, OC48, OC192 Defined• C2 Byte = 0x16 With Scrambling• C2 Byte = oxCF Without (OC-3)


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Quick History of Optical Networking 1958: Laser discovered Mid-60s: Guided wave optics demonstrated 1970: Production of low-loss fibers

Made long-distance optical transmission possible! 1970: invention of semiconductor laser diode

Made optical transceivers highly refined! 70s-80s: Use of fiber in telephony: SONET Mid-80s: LANs/MANs: broadcast-and-select

architectures 1988: First trans-atlantic optical fiber laid Late-80s: EDFA (optical amplifier) developed

Greatly alleviated distance limitations! Mid/late-90s: DWDM systems explode Late-90s: Intelligent Optical networks


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Geometrical Optics Fiber Made of Silica: SiO2 (primarily) Refractive Index, n = cvacuum/cmaterial ncore > ncladding

n~1.45n~1.43


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Basics “Laws”: Refraction and Reflection

Geometrical Optics (cont.)

Reflection: 1r = 1

Refraction: n1sin 1 = n2sin 2 (Snell’s Law)

If 2 = /2: Total Internal Reflection then 1 =sin-1 (n2/n1), “Critical Angle”


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Geometrical Optics (cont.)

Light propagates by total internal reflection Modal Dispersion: Different path lengths cause

energy in narrow pulse to spread out T = time difference between fastest and

slowest ray


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Optical Transmission

AttenuationDispersion

Nonlinearity

Waveform after 1000 kmTransmitted data waveform

Reflectance


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Fiber Attenuation

Two windows: 1310 & 1550 nm

1550 window is preferred for long-haul applications Less attenuation Wider window Optical amplifiers

1310window

1550window


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Fiber Dispersion

Wavelengthl

Dis

pers

ion

ps/

nm-k

m 18

01310 nm 1550nm

Normal fiberNon-dispersion shifted fiber (NDSF) >95% of deployed plant

Reduced dispersion fibersDispersion shifted fiber (DSF)Non-zero dispersion shifted fibers (NZDSF)


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Dispersion

Dispersion causes the pulse to spread as it travels along the fiber

Chromatic dispersion is important for singlemode fiber Depends on fiber type and laser used Degradation scales as (data-rate)2

Modal dispersion limits use of multimode fiber to short distances

Interference


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Single vs. Multimode Fiber Silica-Based Fiber Supports 3 Low-Loss

“Windows”: 0.8, 1.3 , 1.55 m wavelength Multimode Fibers Propagate Multiple Modes of

Lightcore diameters from 50 to 85 mmodal dispersion limitations

Single-mode Fibers Propagate One Mode Onlycore diameters from 50 to 85 mchromatic dispersion limitations (pulse

spreading)


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Polarization Mode Dispersion (PMD)

Most severe in older fiber

Caused by several sources Core shape External stress Material properties

Becomes an issue at OC-192


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Four-Wave Mixing (FWM)

Creates in-band crosstalk that can not be filtered

Problem increases geometrically with Number of s Spacing between s Optical power level

Chromatic dispersion minimizes FWM


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Multiplexing: WDM TDM: Time Division

Multiplexing10Gb/s upper limit

WDM: Wavelength Division MultiplexingUse multiple

carrier frequencies to transmit data simultaneously

12

N1 2 N...

B b/sNB b/s1

2

N

1

2

N

B b/s


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Erbium-Doped Fiber Amplifier (EDFA)

40-80 km

Terminal

Regenerator - 3R (Reamplify, Reshape and Retime)

Terminal

120 km

TerminalTerminal

EDFA - 1R (Reamplify)

Terminal

EDFA amplifies all s

Terminal

Terminal

Terminal

Terminal

Terminal


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EDFA Enables DWDM!

EDFAs amplify all s in 1550 window simultaneously Key performance parameters include

Saturation output power, noise figure, gain flatness/passband

......

980PumpLaser

WDMCoupler

WDMCoupler

EDF

DCF

OpticalIsolator

1480PumpLaser

OpticalFilter

OpticalIsolator

EDF


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Optical Couplers

Combines & splits signals Wavelength independent or dependent

Power(Output1) = Power(Input1) Power(Output2) = (1- ) Power(Input1)

Power splitter if =1/2: 3-dB coupler Used to construct simple optical switches


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Filter selects one wavelength and rejects all others

Multiplexor combines different wavelengths

Router exchanges wavelengths from one input to a different output

Multiplexers, Filters, Routers


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Low insertion loss Loss independent of

SOP Filter passband

independent of temperature

Flat passbands Sharp “skirts” on the

passband

Characteristics of Filters


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Constructive interference at wavelength and grating pitch, a, if a[sin(i) - sin(d)] = m

m = order of the grating

Gratings


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Bragg wavelength is 0 = 2 neff

where is period of grating

If incident wave has wavelength 0, it is reflected by Bragg grating

Bragg Gratings


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Fabry-Perot filter also called F-P interferometer or etalon

Cavity formed by parallel highly reflective mirrors Tunable filter

Fabry-Perot Filters


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Pre-DWDM: Second Gen. Optical Nets

Broadcast and SelectPassive broadcast to all receiversNumber of nodes limited by finite number of

wavelengths and power splitting Wavelength Routing

Allows simultaneous lightpaths using same wavelengths

Power not broadcast to unwanted receivers


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Second Generation Optical Nets

Node

c

Node

A

Node

B

Star

Coupler

1

1 2 3

1 2 3

1 2 3

2

3

A D

B

E

C

1 1

2

Wavelength Conversion

at Node D


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DWDM System Design

15501551155215531554155515561557

01234567

01234567

Amplify DW

DM

Filt

er

Opt

ical

Com

bine

r

15xx nm 1310 nmReamplifyReshapeRetime

Rx Tx1310 nm

Rx

Exte

rnal

M

odul

ator

Laser

15xx nm


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Protection for IP over DWDM

Optical protection is not sufficient Only protects transmission infrastructure

Layer 3 must provide path restoration Opportunity for differentiation at the service level

Optical Cloud


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Eg: 40 DWDM

TX RC

TX

500 km

100 km25 dB RC

TX

TX

RC

RCGSR 12000

SR OC-48 PoS

1

2

3

Error-free transmission over 20,000 kms without SONET regeneration

TX RC

GSR 12000SR OC-48 PoS


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Eg: 16 DWDM and OC-192 Ring

PRS

Working

Protect


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Removing the transport layers

Optical Optical Optical Optical

SONET ATM SONET

ATM

IP

IP IPIP

Lower Cost, Complexity, & Overhead

Traditional

IP Over ATM POS

IP-OG

Today

Tomorrow

IP over Optical Networks (IPO)


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Physical Optics Layer

WDM Layer

Layering (overlay) approaches

SONET

ATM

IP

IP

IP

Direct MPS-based approach

IPSONET

ATM

IP

IP

Traditional SONET-based approaches

IPO: Control Planes


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Packet Label Switch Router (LSR)

Link 1

Link 2

Link 3

Output buffersSwitching fabric3

9

Link 4

Link 5

Link 6

Link 1: label 3 Link 6: label 9

Demux

MuxOptical switching fabric

Lambda Switch Router (SR)

Fiber 1

Fiber 2

Fiber 3

Fiber 4

Fiber 5

Fiber 6

Fiber 2: lambda blue Fiber 4: lambda red

Converters (optional)

Control

OSC

Control information physically coupled

with data

Control information physically decoupled

from data

Ethernet (e.g., outband control

channel/network)

Multi-Protocol Lambda Switching


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Link-state database w. extensions

Extended IGP protocols

(OSPF, IS-IS)

Link Management

Protocol

Signaling protocols

w. extensions

Constraint-Based Routing

Key Elements Overview

Coordinate jointly with LSP control.Wavelength channel

signaling: setup/teardown,protection/ restoration

Added optical metrics

Topology/resource distribution

Neighbor discovery, monitoring

Multi-Protocol Lambda Switching


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Link-Level Restoration Overview

A lightpaths is locally restored by selecting an available pair of channels within the same link

If no channel is available then the end-to-end restoration is invoked

3 10 7 5 7

12

75 47

1 9

4A

B C D

E

Drop port Drop port

14

Original Channel Pair

New Channel Pair


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End-to-End Restoration Overview

A shared backup path is “soft-setup” for each restorable primary path

When local restoration fails, triggers are sent to the end-nodes via signaling

3 10 7 5 7

12

75 4

8 7 9 485

7

1 9

4A

B C D

E

HGF

Drop port Drop port

14

Primary Path

Shared Backup

Path

Local Restoration

Failure


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Wavelength laser

transponders

DemuxMux

Wideband receivers

Gigabit IP Router

IP/PPP/HDLC packet mappings to SONET frames (OC-48, OC-192)

Gigabit IP Router

SON

ET

SON

ET

Point-to-point DWDM links (linear or ring

SONET topologies)

IP routing protocols (OSPF,

BGP)

IP-SONET-WDM using POS


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Optical network

IP address registration

IP border router

UNISONET DCS

IP border router

SONET DCS

Software signaling interface

Endpoint reachability,

service discovery

UNI

NMS control

Border OXC

Border OXC

Core OXC

Modified IP-MPLS protocols or proprietary

signaling/routing

IP-Optical using Signaled Overlay


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IP/MPLS client router

Full peering

Lambda switch routers (SR), switch purely on wavelengths Label edge router

(LER)

“optical LSP”

IP/MPLS client router

OXC (SR)

OXC (SR)

IP and optical domains

Modified IGP and signaling protocols

OXC IP addresses

Router IP addresses

IP-Optical using Peer Model


60

Summary

Internet Core Transport Evolution & Trends SONET Optical Networking: Components Control plane:

Overlay model, peer model Issues: restoration, routing, traffic engineering