Date post: | 17-Jan-2018 |
Category: |
Documents |
Upload: | kristina-hilary-singleton |
View: | 224 times |
Download: | 1 times |
Shivkumar KalyanaramanRensselaer Polytechnic Institute
1
IP over SONET and Optical Networks
Shivkumar KalyanaramanRensselaer Polytechnic Institute
[email protected] http://www.ecse.rpi.edu/Homepages/shivkuma
Based in part on slides of Nick McKeown (Stanford)
Shivkumar KalyanaramanRensselaer Polytechnic Institute
2
Internet Core Transport Evolution & Trends SONET Optical Networking: Components Control plane:
Overlay model, peer model Issues: provisioning, restoration, routing, traffic
engineering
Overview
Shivkumar KalyanaramanRensselaer Polytechnic Institute
3
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
Shivkumar KalyanaramanRensselaer Polytechnic Institute
4
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
Shivkumar KalyanaramanRensselaer Polytechnic Institute
5
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
Shivkumar KalyanaramanRensselaer Polytechnic Institute
6
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
Shivkumar KalyanaramanRensselaer Polytechnic Institute
7
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
Shivkumar KalyanaramanRensselaer Polytechnic Institute
8
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)
Shivkumar KalyanaramanRensselaer Polytechnic Institute
9
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
Shivkumar KalyanaramanRensselaer Polytechnic Institute
10
STS-1 Headers
90 Bytes90 BytesOr “Columns”Or “Columns”
99RowsRows
Section Overhead (SOH)
Line Overhead (LOH)Path Overhead (POH)
Shivkumar KalyanaramanRensselaer Polytechnic Institute
11
Headers: Section Overhead (SOH)
A1=0xF6
A2A2=0x28=0x28
J0/Z0J0/Z0STS-IDSTS-ID
B1B1BIP-8BIP-8
E1E1OrderwireOrderwire
F1F1UserUser
D1D1Data ComData Com
D2D2Data ComData Com
D3D3Data 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
Shivkumar KalyanaramanRensselaer Polytechnic Institute
12
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
D7D7Data ComData Com
D8D8Data ComData Com
D9D9Data ComData Com
D10D10Data ComData Com
D11D11Data ComData Com
D12D12Data ComData Com
S1S1SyncSync
M0M0REIREI
E1E1OrderwireOrderwire
RcvRcvSOHSOH
XmtXmtSOHSOHXmXm
ttSOSOHH
XmXmtt
LOLOHH RcvRcv
SOHSOH
RcvRcvLOHLOH
Shivkumar KalyanaramanRensselaer Polytechnic Institute
13
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
Shivkumar KalyanaramanRensselaer Polytechnic Institute
14
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 …
Shivkumar KalyanaramanRensselaer Polytechnic Institute
15
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
Shivkumar KalyanaramanRensselaer Polytechnic Institute
16
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 !!
Shivkumar KalyanaramanRensselaer Polytechnic Institute
17
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
Shivkumar KalyanaramanRensselaer Polytechnic Institute
18
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
Shivkumar KalyanaramanRensselaer Polytechnic Institute
19
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
Shivkumar KalyanaramanRensselaer Polytechnic Institute
20
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
Shivkumar KalyanaramanRensselaer Polytechnic Institute
21
Protection Topologies - Linear Two nodes connected to each other with two or
more sets of links
Working Protect Working Protect
(1+1) (1:n)
Shivkumar KalyanaramanRensselaer Polytechnic Institute
22
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
Shivkumar KalyanaramanRensselaer Polytechnic Institute
23
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
Shivkumar KalyanaramanRensselaer Polytechnic Institute
24
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)
Shivkumar KalyanaramanRensselaer Polytechnic Institute
25
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
Shivkumar KalyanaramanRensselaer Polytechnic Institute
26
Geometrical Optics Fiber Made of Silica: SiO2 (primarily) Refractive Index, n = cvacuum/cmaterial ncore > ncladding
n~1.45n~1.43
Shivkumar KalyanaramanRensselaer Polytechnic Institute
27
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”
Shivkumar KalyanaramanRensselaer Polytechnic Institute
28
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
Shivkumar KalyanaramanRensselaer Polytechnic Institute
29
Optical Transmission
AttenuationDispersion
Nonlinearity
Waveform after 1000 kmTransmitted data waveform
Reflectance
Shivkumar KalyanaramanRensselaer Polytechnic Institute
30
Fiber Attenuation
Two windows: 1310 & 1550 nm
1550 window is preferred for long-haul applications Less attenuation Wider window Optical amplifiers
1310window
1550window
Shivkumar KalyanaramanRensselaer Polytechnic Institute
31
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)
Shivkumar KalyanaramanRensselaer Polytechnic Institute
32
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
Shivkumar KalyanaramanRensselaer Polytechnic Institute
33
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)
Shivkumar KalyanaramanRensselaer Polytechnic Institute
34
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
Shivkumar KalyanaramanRensselaer Polytechnic Institute
35
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
Shivkumar KalyanaramanRensselaer Polytechnic Institute
36
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
Shivkumar KalyanaramanRensselaer Polytechnic Institute
37
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
Shivkumar KalyanaramanRensselaer Polytechnic Institute
38
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
Shivkumar KalyanaramanRensselaer Polytechnic Institute
39
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
Shivkumar KalyanaramanRensselaer Polytechnic Institute
40
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
Shivkumar KalyanaramanRensselaer Polytechnic Institute
41
Low insertion loss Loss independent of
SOP Filter passband
independent of temperature
Flat passbands Sharp “skirts” on the
passband
Characteristics of Filters
Shivkumar KalyanaramanRensselaer Polytechnic Institute
42
Constructive interference at wavelength and grating pitch, a, if a[sin(i) - sin(d)] = m
m = order of the grating
Gratings
Shivkumar KalyanaramanRensselaer Polytechnic Institute
43
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
Shivkumar KalyanaramanRensselaer Polytechnic Institute
44
Fabry-Perot filter also called F-P interferometer or etalon
Cavity formed by parallel highly reflective mirrors Tunable filter
Fabry-Perot Filters
Shivkumar KalyanaramanRensselaer Polytechnic Institute
45
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
Shivkumar KalyanaramanRensselaer Polytechnic Institute
46
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
Shivkumar KalyanaramanRensselaer Polytechnic Institute
47
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
Shivkumar KalyanaramanRensselaer Polytechnic Institute
48
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
Shivkumar KalyanaramanRensselaer Polytechnic Institute
49
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
Shivkumar KalyanaramanRensselaer Polytechnic Institute
50
Eg: 16 DWDM and OC-192 Ring
PRS
Working
Protect
Shivkumar KalyanaramanRensselaer Polytechnic Institute
51
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)
Shivkumar KalyanaramanRensselaer Polytechnic Institute
52
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
Shivkumar KalyanaramanRensselaer Polytechnic Institute
53
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
Shivkumar KalyanaramanRensselaer Polytechnic Institute
54
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
Shivkumar KalyanaramanRensselaer Polytechnic Institute
55
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
Shivkumar KalyanaramanRensselaer Polytechnic Institute
56
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
Shivkumar KalyanaramanRensselaer Polytechnic Institute
57
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
Shivkumar KalyanaramanRensselaer Polytechnic Institute
58
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
Shivkumar KalyanaramanRensselaer Polytechnic Institute
59
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
Shivkumar KalyanaramanRensselaer Polytechnic Institute
60
Summary
Internet Core Transport Evolution & Trends SONET Optical Networking: Components Control plane:
Overlay model, peer model Issues: restoration, routing, traffic engineering