Presentation on theme: "ITU-T Kaleidoscope 2010 Beyond the Internet"— Presentation transcript:
1ITU-T Kaleidoscope 2010 Beyond the Internet ITU-T Kaleidoscope 2010 Beyond the Internet? - Innovations for future networks and servicesIntroducing Elasticity and Adaptation into the Optical Domain Toward More Efficient and Scalable Optical Transport NetworksM. Jinno, T. Ohara, Y. Sone, A. HiranoO. Ishida, and M. TomizawaNTT Network Innovation Labs.Pune, India, 13 – 15 December 2010
2Outline Background: Growing anticipation SE-conscious optical networkingEarly initiatives by ITU-TElastic optical path network as a candidate to support future Internet and servicesAdoption scenarios from rigid optical networks to elastic optical path networkPossible standardization study items and some solutions relevant to future ITU-T activities
3Background (1): Successful Deployment of Optical Networks Worldwide intensive R&D activitiesContinuous initiative by ITU-T toward OTNs and ASONsG.709 OTN augmentation to transport 100 GE traffic100 M1 G10 G100 G1 T10 T100 T198019902000201020200.010.1110Year of commercialization in JapanPer fiber capacity (b/s)Spectral efficiency (b/s/Hz)100 Gb/s x 80(projected)40 Gb/s x 4010 Gb/s x 80WDMTDMOptical networks have become widely spread and have assumed a role as mission critical infrastructures in our information society.This is due to worldwide intensive R&D activities and continuous initiatives by ITU-T SG 15 toward optical transport networks (OTNs) and automatically switched optical networks (ASONs).More recently, in close collaboration with the IEEE, the ITU-T has augmented its G.709 OTN standard to transport 100G Ethernet traffic over wide area networks.
4Background (2): Slowing Down of SE Improvement Fixed optical amplifier bandwidth (~ 5 THz)Per fiber capacity increase has been accomplished through boosting SE (bit rate, wavelength, symbol per bit, state of polarization)Bit loading higher than that for QPSK causes rapid increase in SNR penalty, and results in shorter optical reachSE improvement for P2P is slowing down, meaning higher rate data need more spectrum0.010.1110020030040050010Bit rate per channel (Gb/s)Relative optical reach with constant energy per bit (a.u.)Spectral efficiency (b/s/Hz)DP-QPSKDP-16QAMDP-64QAMDP-256QAMDP-1024QAMQPSKBPSK600@25 GbaudOptical amplifier bandwidth (~ 5 THz)TDMWDMMulti-level mod.At a fixed optical amplifier bandwidth, typically 5 THz, increases in the per fiber capacity have been achieved through boosting of the spectral efficiency by means of increasing the signal bit rate, wavelengths, symbols per bit, and states of polarization.As a result, a cutting edge transport system employing dual-polarization and QPSK modulation will have a spectral efficiency reaching 2 b/s/Hz.Unfortunately, it is well known that bit loading higher than that for QPSK to further increase the channel capacity causes a rapid increase in the SNR penalty.Under the limited fiber launched power necessary to avoid excessive nonlinear signal distortions, this SNR penalty results in a shorter optical reach.Due to this, despite the potential for more powerful forward error correction, FEC and a lower noise amplifier, we need to concede that the pace of improvement in spectral efficiency will be slowing down in the era beyond 100 Gb/s.Multiplexing technology evolutionPDM
5Background (3): Growing Concern of SE in Networking Fiber capacity crunch concerns are driving optical networking toward a spectral-efficiency-conscious design philosophyRight-sized optical bandwidth is adaptively allocated to an end-to-end optical pathSpectral-efficiency-conscious, adaptive networking approach has attracted growing interestEx. Elastic optical path network2008.92010.92009.92009.32010.32011.3ECOC2008“Demonstration of novel spectrum-efficient elastic optical path network ….” (NTT)Now, we should recognize that the spectrum resources of optical fibers are not limitless as previously thought but rather precious resources.This idea is driving optical networking toward a spectral-efficiency-conscious design philosophy,in which the right-sized optical bandwidth is adaptively allocated to an end-to-end optical path by “slicing off” the necessary spectral resources on a given route in the network.For example, NTT has recently proposed and experimentally demonstrated the “Elastic optical path network”.Since then, this spectral-efficiency conscious, adaptive optical networking approach has attracted growing interest and a number of relevant symposia and workshops have been held.ECOC2009 Symposium“Dynamic multi-layer mesh network”OFC2010 WS“How can we groom and multiplex data for ultra-high-speed transmission”OECC2010 Symposium“Future optical transport network”ECOC2010Symposium“Towards 1000 Gb/s”OFC2011WS“Spectrally/bit-rate flexible optical network”
6Expected Early ITU-T Initiatives Early ITU-T initiatives on studying possible extension of OTN and ASON standards are indispensable.Greatly support rapid advance and adoption of spectrally-efficient and adaptive optical networksStarting point regarding studying possible extension of OTN and ASON standards in terms of network efficiencyClarify what should be inherited, what should be extended, and what should be createdThe introduction of elasticity and adaptation will be a big leap forward from conventional rigid and fixed optical networks.We, therefore, believe that early initiatives by the ITU-T will be indispensable in studying possible extension of the OTN and ASON standards.This will greatly support the rapid advance and adoption of spectrally-efficient and adaptive optical networks.In the remaining part of my presentation, I will briefly introduce the elastic optical path network and its possible adoption scenarios.Then, as the starting point regarding studying the possible extension of OTN and ASON standards in terms of network efficiency,I will clarify what should be inherited, what should be extended, and what should be created.
7Elastic Optical Path Network Spectrum-efficient transport of 100 Gb/s services and beyond through introduction of elasticity and adaptation into optical domainAdaptive spectrum resource allocation according toPhysical conditions on route (path length, node hops)Actual user traffic volumeSE-conscious adaptive signal modulationSE-conscious elastic channel spacing250 km400 Gb/s100 Gb/s1,000 kmFixed format, gridAdaptivemodulationQPSK200 Gb/s16QAMPath lengthBit rateConventionaldesignElastic optical path networkThe aim of the elastic optical path network is to provide spectrum-efficient transport of 100-Gb/s services and beyond through the introduction of elasticity and adaptation into the optical domain.If based on the conventional design philosophy, every optical path is aligned on a fixed grid regardless of the path length, bit rate, and actual client traffic volume.By taking advantage of spectral-efficiency-conscious adaptive signal modulation and elastic channel spacing, elastic optical path networks yield significant spectral-savings as shown in this figure.For shorter optical paths, which suffer from less SNR degradation, we employ a more spectrally-efficient modulation format, such as 16QAM.For client traffic that does not fill the entire capacity of a wavelength, the elastic optical path network provides right-sized intermediate bandwidth, such as 200 Gb/s.Combined with elastic channel spacing, where the required minimum guard band is assigned between channels, elastic optical path networks accommodate a wide range of traffic in a spectrally-efficient manner.Elastic channelspacing
8Enabling Hardware Technologies (1) Rate and Reach Flexible Transponder Introduce coherent detection followed by DSPOptimizing 3 parameters provides required data rate and optical reach while minimizing spectral width(Symbol rate) x (Number of modulation levels) x （Number of sub-carriers）Flexible reachChange the number of bits per symbol with high-speed digital-to-analogue converter and IQ-modulatorFlexible rateOptical OFDM is spectrally-overlapped orthogonal sub-carrier modulation schemeCustomize number of sub-carriers of OFDMFlexible reach transmitter100 G400 GFlexible rate/reach transmitter100 G~400 GUsing the next two slides, I will present enabling hardware technologies of the elastic optical path network.The first technology is a rate and reach flexible optical transponder.Introduction of coherent detection followed by DSP will yield a novel degree of freedom in designing transponders.By optimizing 3 parameters, the symbol rate, the number of modulation levels, and the number of sub-carriers, we can provide the required data rate and optical reach while minimizing the spectral width.For example, we can achieve a flexible reach transmitter by changing the number of bits per symbol with a high-speed digital-to-analog converter and IQ-modulator.Optical OFDM is a spectrally-overlapped orthogonal sub-carrier modulation scheme.We can achieve a flexible-rate transmitter by customizing the number of sub-carriers of the OFDM signal.
9Enabling Hardware Technologies (2) Bandwidth Agnostic WXC Introduce bandwidth-variable WSS based on, e.g., LCoSRequired minimum spectrum window (optical corridor) is open at every node along optical pathRequired width of optical corridor is determined by factoring in signal spectral width and filter clipping effect accumulated along nodes.BVWXCWSStransponderOutputfiberInputBandwidth agnostic WXCSpatial light modulatorBandwidth variablewavelength selective switch (WSS)GratingOptical freq.mittanceTrans-400 Gb/s400 Gb/s40 Gb/s40 Gb/s100 Gb/sThe second technology is a bandwidth agnostic wavelength cross-connect.Bandwidth agnostic wavelength cross-connects, WXCs can be achieved by using a continuously bandwidth-variable Wavelength selective switch (WSS) based on, for example, liquid crystal on silicon (LCoS) technology, as a building block.In a bandwidth-variable WSS, the incoming optical signals with different optical bandwidths and center frequencies can be routed to any of the output fibers.These technologies allow us to open the required minimum spectrum window at every node along the optical path.
11Step-by Step Adoption Scenario: Higher Rate Client Triggered (e. g Step-by Step Adoption Scenario: Higher Rate Client Triggered (e.g., 400 Gb/s)Possible next Ethernet rate, 400 G, could appear around 2015.Optical reach and SE are not independent parameters in 400 G era.Balancing optical reach and SE in 400 G systems will most likely require elastic spectral allocationDistance adaptive spectral allocationHigh-SE multi-reach traffic accommodationP2PNetworkEqually-spacedNon-ITU-T gridHigh-SE 400 G accommodationP2P1 G10 G100 G1 T199520002005201020152020Year of standardizationBit rate (b/s)GE10 GE40 GE100 GEOTU1OTU3OTU2OTU4OTU5(projected)STM256400 GESTM64Elasticchannel spacingHigh-SE multi-rate traffic accommodationThis graph shows the standardization trend of Ethernet and OTN interfaces over time.If we simply extrapolate this trend, we see that the possible next Ethernet rate of, say 400 Gb/s, will appear around 2015.Since optical reach and spectral efficiency are not independent parameters in the 400G era,in order to balance these parameters, 400 Gb/s point-to-point WDM systems will most likely requirean equally-spaced non ITU-T grid, orelastic channel spacing if multiple rate traffic of 100 G and 400 G are accommodated.When applied to ring or mesh networks, different path lengths between source and destination pairs will bring distance-adaptive spectral allocation for network-wide spectral savings.Finally, dynamic spectral allocation to provide optical bandwidth-on-demand service and cost-effective high-availability transport service will be achieved through sophisticated operation based on the optical version of the link capacity adjustment scheme (LCAS) and bandwidth-squeezed highly-survivable restoration technologies.Dynamic spectral allocationOptical BoD, highly survivable restoration
12Earlier Adoption Scenario: Large-Scale 100 Gb/s ROADM Design Facilitation Even employing DP QPSK modulation, transmitting 100 Gbps signals over multiple hops of ROADMs on a 50 GHz grid is still tough task.Distance adaptive spectrum allocation will facilitate 100 Gb/s ROADM design for longer pathsSignificant spectral-saving when compared with the worst-case design on a 100 GHz grid.112 Gb/s DP-QPSK112Gb/s DP-16QAM2550751001234567891011121314Number of node hopsAllocated spectral width [GHz]100 GHz gridDistanceadaptiveSpectrum allocation mapsNetwork utilization efficiency1234567-45%100 GHz gridDistanceadaptiveRequired total spectrum at most occupied link (THz)Distance–adaptive spectrum allocation121112354678910The other scenario is an earlier adoption scenario to facilitate 100 Gb/s ROADM design.Even employing a spectrally-efficient dual-polarization QPSK modulation format, transmitting 100 Gbps signals over multiple hops of ROADMs on a 50 GHz grid is still a tough task, especially for large scale networks.One way to relax the system design while keeping a reasonable spectral efficiency would be to introduce a non-ITU-T grid or distance adaptive spectral allocation.The middle figure shows the required spectral resources for 100 Gb/s signals as a function of the number of ROADM hops when non-ideal ROADM filtering characteristics and component frequency offsets are taken into account.If we consider the worst-case design policy and the conventional frequency grid standard, we have to employ a 100 GHz grid to support a longer optical path with node hops of 10 or more.The distance adaptive spectrum allocation with elastic channel spacing will alleviate 100 Gb/s ROADM design for longer paths, and result in significant spectral-savings when compared with the worst-case design on a 100 GHz grid.
14OTN Network Architecture G.872 “Architecture of optical transport networks” specifies functional architecture of OTN from network level viewpointLayered structure of Optical Channel (OCh), Optical Multiplex Section (OMS), and Optical Transmission Section (OTS)Although data rate, modulation format, and spectral width of optical path in elastic optical path network may change, elastic optical path is naturally mapped into OChSee no significant impact on current G.872OMSOTSMuxDemuxTxRx3RODUflex, ODUkOTUflex, OTUk-xvOChBandwidth agnostic WXCThe first item I’d like to discuss is the Optical Transport Network, or OTN.ITU-T Recommendation G.872 “Architecture of optical transport networks” specifies the functional architecture of OTN from a network level viewpoint.G.872 defines an optical network layered structure that comprises an Optical Channel (OCh), Optical Multiplex Section (OMS), and Optical Transmission Section (OTS).Although the data rate, modulation format, and spectral width of an optical path in an elastic optical path network may change according to the user demand and network conditions, an elastic optical path is naturally mapped into the OCh of the current OTN layered structure.We, therefore, see no significant impact on the current G.872 when introducing the elastic optical path concept.
15OTN Interfaces and Mapping: Current OTN G.709 “Interfaces for the optical transport network (OTN)” specifies Interfaces and mappings of OTNConflicting operator requirementsTransport a wide variety of client signals while minimizing types of line-interfaces in order to reduce capital expenditures, which are dominated by line-interface costs.LO/HO ODUs and ODUflex can address these conflicting requirements.LO ODU offers versatility to accommodate various client signals and HO ODU offers simplicity in terms of physical interface.100 Gb/sODU 4OTU 4ODU 0OTU 3The interfaces and mappings of OTN are specified in G.709 “Interfaces for the optical transport network (OTN).”Originally the OTN specified client signal mapping into ODUk (k=1, 2, 3) [where k is one, two, or three], which have bit rates of approximately 2.5 Gb/s, 10 Gb/s, and 40 Gb/s, and their multiplexing to ODUk with a higher bit rate if necessary.The multiplexed ODUk signal is then transported as an OTUk signal with an FEC code.Although network operators should transport a wide variety of client signals, they must minimize the types of line-interfaces in order to reduce the capital expenditures, which are dominated by line-interface costs.The concept of the Lower Order (LO)/Higher Order (HO) ODU and ODUflex can address these conflicting requirements.The LO ODU [low order ODU] offers versatility to accommodate various client signals and the HO ODU [high order ODU] offers simplicity in terms of the physical interfaces.ODU 310 Gb/sODU 2OTU 2OChODUflex (L)ODU 1OTU 11 Gb/sClientsignalMapMuxMapE/OODU (L)ODU (H)ODUOTUOCh
16OTN Interfaces and Mapping: Possible Flexible OTU Extension Rate-flexible OCh enables cost-effective transport of various client signals in fully optical domain w/o electrical multiplexing and groomingIntroduction of rate-flexible OTUs (OTUflex) and rate-flexible HO ODUs (HO ODUflex).Rate-flexibletransponder1 Tb/sODUflex (L)ODUflex (H)ODUflexOTUflexOTUflex100 Gb/sODU 4OTU 4OChOTU 3Once a rate-flexible OCh based on optical OFDM transponders and bandwidth-agnostic ROADMs/WXCs is introduced, cost-effective transport of various client signals will be enabled in the fully optical domain without intermediate electrical multiplexing and grooming processes.As a natural step toward a rate-flexible OCh, we may need to introduce rate-flexible OTUs (OTUflex) as well as rate-flexible HO ODUs (HO ODUflex).The OTUflex and HO ODUflex will be specified in the region of over Gb/s depending on the maturity of the device technology at the time.ODU 310 Gb/sODU 2OTU 2ODU 1OTU 1Conventionaltransponder1 Gb/sODU 0ClientsignalMapMuxMapE/OODU (L)ODU (H)OTUOCh
17Physical Layer Specification (1): Possible Frequency Grid Extension f=193.1 THzf=193.2 THzf=193.0 THz100 GHz50 GHz25 GHz12.5 GHz12345678-8-7-6-5-4-3-2-1Frequency grid (G.694.1)G “Spectral grids for WDM applications: DWDM frequency grid”Anchored to THz, and supports various channel spacings of 12.5 GHz, 25 GHz, 50 GHz, and 100 GHzExplicitly allocate spectral resources to optical pathTo quantize continuous spectrum into contiguous frequency slots with appropriate slot width.13456782-4-3-2-8-7-6-5-1Frequency slot (12.5 GHz width)Next I’d like to discuss the physical aspects.The current ITU-T frequency grid specified in G “Spectral grids for WDM applications: DWDM frequency grid” is anchored to THz, and supports various channel spacings of 12.5 GHz, 25 GHz, 50 GHz, and 100 GHz.One way to explicitly allocate the spectral resources to an optical path may be to quantize the continuous spectrum into contiguous frequency slots with an appropriate slot width.For example, the ITU-T frequency grid with a channel spacing of 12.5 GHz should be interpreted as a frequency slot on the grid with a slot width of 12.5 GHz, as shown in the figure to the lower right.We can flexibly allocate the necessary spectral resources by assigning the required number of contiguous frequency slots.HL50 GHz125 GHz37.5 GHzFrequency slot allocation
18Physical Layer Specification (2): Possible Intra-Domain Application Extension Conventional systems:Target distance and capacity are a fixed set of valuesElastic optical path network:Line interfaces will have multi-reach functionalityTrade-off between optical reach and SEVariable sets of parameters for target distance and capacity(TD1, TC1)DistanceCapacity(TD2, TC2)(TD3, TC3)Elastic optical path network(TD, TC)DistanceCapacityConventional optical networkTD: Target distanceTC: Target capacityBR: Bit rate40.10G-20L652A(C)Target Capacity=40 x 10 Gb/sTarget distance=20-span,long-haul G.652.A-fiber (C-band)Recommendation G Longitudinally compatible intra-domain DWDM applicationsEx.Considering the advanced functionalities that we are trying to achieve, it is natural to start with the intra-domain single vender longitudinal compatibility approach for physical layer specifications of elastic optical path networks, rather than the multi-vendor transversal compatibility approach.Let us take line interface specifications for example.In conventional systems, the target distance and capacity of line interfaces are a fixed set of values and defined as application codes.For example, G defines “Longitudinally Compatible Intra-Domain DWDM Applications.”This application indicates a target capacity of a 40-channel system with signals of the 10 G payload class, and a target distance of 20 long-haul spans of G.652A fiber.If we recall that line interfaces of elastic optical path networks will have a multi-reach functionality and there will be a trade-off between the optical reach and spectral efficiency, there can be a variable set of parameters for the target distance and capacity for an application code of the line-interface.This unique feature may bring additional degrees of freedom in defining the physical layer specifications and may result in a reduction in the capital expenditure.
19ASON Control PlaneG. 805, G.7713, G.7714, and G.7715 provide network resource model, requirements, architecture, and protocol neutral specifications for automatically switched optical networks (ASONs),Based on functional models for SDH (G.803) and OTN (G.872)No significant impact on current ASON standards when introducing distributed control plane into elastic optical path networksThe third item is the Automatically Switched Optical Network, or ASON.The ITU-T Recommendations on ASON provide a network resource model, requirements, architecture, and protocol neutral specifications for automatically switched optical networks with a distributed control plane.We have already examined G.872 in the previous slide. As a result of preliminary investigation we consider that there will be no significant impact on the current ASON standards when introducing a distributed control plane into elastic optical path networks, although further studies are still necessary.
20Possible Technology-Specific Extension of Routing and Signaling Need discussion on extension of GMPLS protocols in IETF and OIF with ITU-T SG15Define new parameters in signaling messagesLabel request objectUpstream label object…Explicit route objectSender TSpec objectLabel objectRecord route objectFlow spec objectPATH messageRESV messageSwitching type:spectrum switching capableParameters in objectsLabel:(start slot, end slot)As for the technology-specific aspects of routing and signaling in elastic optical path networks, we should discuss possible extension of GMPLS protocols in the IETF and the OIF in close cooperation with ITU-T SG 15.We may define a new switching type “spectrum switching capable” and a new label “start slot number and end slot number” in signaling messages.We will also introduce new parameters, the “symbol rate, number of sub-carriers, and modulation level” in the Sender TSpec and Flow Spec Objects.Modulation format:(symbol rate, no. of sub-carriers, modulation level)
21Conclusions Elastic optical path network Possible adoption scenarios Required minimum spectral resources are adaptively allocatedPossible adoption scenariosStudy items relevant to future standardization activities of ITU-T SG15Possible extension of OTN, physical layer, and ASON standards in terms of network efficiency