Packet-Optical Integration: The Key to Evolving Towards Packet Enabled Agile Optical Networkds


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The operator's paradox, for the past several years now, has been that while there is an explosion in data traffic volumes to the tune of 45-65% yearly, the corresponding revenue growth is in the single digits at best. To bridge this gap between rising operating costs (spurred by increased network capacity demands) and relatively flat revenues, providers must assess how to better architect their...

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Packet-Optical Integration: The Key to Evolving Towards Packet Enabled Agile Optical Networkds

  1. 1. Packet-Optical Integration: The Key to Evolving Towards Packet-Enabled Agile Optical Networks Vishal Sharma, Ph.D., Principal Technologist & Consultant, Metanoia, Inc., Mountain View, CA 94041, USA. Mark Allen, Ph.D., Director of Systems Engineering, Infinera Corporation, 169 Java Drive, Sunnyvale, CA 94089, USA. Table of Contents1 Introduction: The Carrier Cost-Capacity Crunch!.......................................................... 22 Major Solution Drivers: What is the Impetus? ................................................................ 23 Defining Characteristics of a Packet-Optical Solution ................................................... 44 Three Key Areas of Advancement: Photonic Sub-Systems, Systems, and Software ........ 4 4.1 ROADMs: Reconfigurable, Agile, and Gridless, & PICs......................................... 4 4.2 Packet-Optical Transport Systems (The New P-OTS!) -- Requirements, Architectures and Trade-Offs .......................................................................................... 6 4.3 Photonic Control-Plane Software: Advances and Challenges.................................. 75 Open Issues and Carrier Concerns.................................................................................. 86 References ........................................................................................................................ 9A Metanoia, Inc. Technology Paper Page 1 of 10 Metanoia, Inc., 888 Villa Street, Suite 500, Mountain View, CA 94041, USA. © 2011 Metanoia, Inc.
  2. 2. 1 Introduction: The Carrier Cost-Capacity Crunch!The operators paradox, for the past several years now, has been that while there is anexplosion in data traffic volumes to the tune of 45-65% yearly, the corresponding revenuegrowth is in the single digits at best. To bridge this gap between rising operating costs(spurred by increased network capacity demands) and relatively flat revenues, providersmust assess how to better architect their networks -- from routers/switches to the opticallayer -- to reduce the transport-cost per bit, to conserve space and power, and to improvenetwork performance so as to lower the opex. (Indeed, statistics show that serviceproviders spend almost 5 opex dollars for each capex dollar! [1]). Furthermore, they mustoptimize their networks to efficiently carry high growth services like Internet access,packet traffic from 3G/4G mobile wireless networks, and video.Achieving this efficiency entails a tighter integration between the packet and theoptical/photonic layers, since the photonic layer is the cheapest per-bit, per function, thusmotivating the packet-optical integration, we discuss in this paper.We start by examining the defining characteristics of a packet-optical solution, and themajor solution drivers, and then focus on the architecture of 3 key components of thesolution -- wavelength transport and switching infrastructure, systems and ASICs, andcontrol- and management-plane software. Having discussed these, we outline some openissues and key carrier concerns.2 Major Solution Drivers: What is the Impetus?Technological advances (such as cloud computing, remote diagnostics, multimediacollaboration), bandwidth intensive applications (such as video services with HD, CarrierEthernet enterprise services, and remote data backup and disaster recovery), and fastconnection speeds (which, per Nielsens Law (cf. Figure 1), double every 21 months) leadtoday to a proliferation of data packets and drive the demand for a better networkingsolution.In addition, some key enterprise trends contribute to this traffic. For instance, almost 95%of enterprise traffic is now Ethernet-based. Indeed, business Ethernet port demand was up43% in 2008 alone. Further, almost 80% of traffic now leaves the enterprise (the reverseof what it was just a little over a decade ago) implying a much greater load in the metroand core [2].A Metanoia, Inc. Technology Paper Page 2 of 10 Metanoia, Inc., 888 Villa Street, Suite 500, Mountain View, CA 94041, USA. © 2011 Metanoia, Inc.
  3. 3. Figure 1 Neilsen’s Law of Internet Bandwidth: Predicted in 1998, shownaccurate and consistent for over a decade (From Jakob Neilsen’s Alertbox )Thus, a key impetus for carriers is to increase the effectiveness and efficiency oftransporting these packets over an optical transport network in the WAN environment.Today, the IP/Ethernet packets are wrapped into SONET/SDH or G.709 TDM circuits,and transported over wavelengths on an optical infrastructure. One disadvantage of this isthat when all switching occurs in a Layer 3 router/switch rather than judiciouslyleveraging Layer 2 Ethernet or Layer “2.5” MPLS switching, the cost of the networkbegins to increase. Consequently, control layer mechanisms, such as Multi-ProtocolLabel Switching-Transport Profile, MPLS-TP (e.g. RFCs 5654, 5317, 5718, 5860; [3]),or Provider-Backbone Bridging-Traffic Engineering, PBB-TE (IEEE 802.1Qay standard),are becoming important. Plus, the transport of IP/Ethernet over optical infrastructure ismoving to sending native IP/Ethernet over wavelengths via WDM, which requires newerpacket-optical solutions.The particular solution adopted will be dictated by a number of factors. For example, thebalance between the extent of connection-oriented (TDM) traffic and pure datagramtraffic, the existing capital investment in SONET/SDH ADMs, ROADMs, switches androuters, the degree of equipment consolidation needed/desired to reduce opex, desire touse the wavelengths better, the OAMP&T (operations, administration, maintenance,performance and troubleshooting) provided by the deployed technologies, and whetherIP/MPLS expertise and transport expertise resides in a common team or in different partsof the providers’ organization.A Metanoia, Inc. Technology Paper Page 3 of 10 Metanoia, Inc., 888 Villa Street, Suite 500, Mountain View, CA 94041, USA. © 2011 Metanoia, Inc.
  4. 4. 3 Defining Characteristics of a Packet-Optical SolutionSo what are the key ingredients being looked upon by operators in a packet-opticalsolution? It turns out that the following 4 elements are becoming table stakes:i) Reconfigurable Optical Add/Drop Multiplexer (ROADM) infrastructure with supportfor routing wavelengths at multi-degree junctions, as well as the simpler two degreenodes [4].ii) The ability to efficiently carry existing SONET/SDH services without compromisingsupport for high-growth packet and OTN traffic (see Optical Transport Network – ITU-TG.709 for more discussion on OTN standards).iii) Connection-oriented Layer 2 Ethernet switching and aggregation (for an exposition ofOptical Ethernet, consult our article in the Feb. 2010 issue of Photonic Tech. Briefs, Carrier-grade OAM -- merging what exists in the optical domain with what exists inthe packet domain to give an operator a comprehensive overall view of the network.Thus, there is emerging a general industry consensus on the requirements of a Packet-Optical Transport System (POTS). However, the jury is still out on how such a system isfinally realized, as we explain when discussing POTS in the section ahead.4 Three Key Areas of Advancement: Photonic Sub-Systems, Systems, andSoftwareThe development of packet-optical solutions has involved advancements in 3 key areas:wavelength-transport and switching infrastructure, systems and ASICs (such as Packet-Optical Transport Systems), and control and management plane software for controlplane automation and management. In the following, we consider each of this one-by-one.4.1 ROADMs: Reconfigurable, Agile, and Gridless, & PICsIn this subsection, we focus on ROADMs and PICs, two key components of thewavelength transport infrastructure.Reconfigurable Optical Add-Drop Multiplexers (ROADMs) have played a key role inmoving the transport network toward greater agility/flexibility, by reducing the manualintervention needed to setup new lightpaths. As a data point, as per Infonetics Research’sROADM Component tracking report, ROADM-based optical network revenue was thefastest growing in the last couple years, with a 46% CAGR between 2005 and 2009,while in the same period the overall optical equipment revenue grew only at 8% CAGR.A ROADM is composed of a number of sub-systems such as a Wavelength SelectiveSwitches (WSSs), optical amplifiers, optical channel monitors, transponders, and controlA Metanoia, Inc. Technology Paper Page 4 of 10 Metanoia, Inc., 888 Villa Street, Suite 500, Mountain View, CA 94041, USA. © 2011 Metanoia, Inc.
  5. 5. and management software. A ROADM eliminates costly optical-to-electrical conversionsat intermediate nodes, by allowing wavelengths to pass intermediate nodes in the opticaldomain.Figure 2 Conceptual Operation of a Wavelength Selective SwitchFirst generation ROADMs allowed a lightpaths direction to be changed, while itswavelength remained fixed. They were typically 2-dimensional nodes, that enabled ringarchitectures. Subsequent ROADMs had higher degrees, of between 4-8, allowing formesh architectures.Second generation ROADMs used tunable lasers and wavelength selective switches(WSSs), thus, allowing both the direction and the wavelength of a lightpath to bechanged. WSS modules are the building blocks for ROADMs that can handle anywavelength on any port (and so are known as colorless) and can connect signals flowingin any direction on any port to any other port (hence directionless).The next-generation of ROADMs will be gridless and contentionless. A contentionlessROADM allows multiple copies of a given wavelength (coming from differentdirections) to be dropped at a node, while a gridless ROADM has the capability toaccommodate wavelengths that do not fit on the ITU 50 GHz or 100 GHz grid, but willutilize a flexgrid with a less rigid channel spacing (where some or all of the channelscould use more than the standard 50GHz bandwidth). This allows for variable channelwidths, enables operators to efficiently use spectrum to maximize fiber capacity. Theywill also incorporate fast switching speeds to decrease latency, and superior opticalchannel monitoring at the ROADM ports to better regulate signal power.Photonic Integrated Circuits (PICs) have shown to be very effective in reducing the cost(both Opex and Capex) of the DWDM systems deployed by operators [5]. For example,Infinera’s PIC based transport system is the #1 most widely deployed DWDM system inNorth America and includes a PIC-based Line Module with more than 100 opticalcomponents (lasers, modulators, wavelength lockers, etc) integrated on a singlemonolithic Indium Phosphide chip of approximately 5mm square. Next generation PICsA Metanoia, Inc. Technology Paper Page 5 of 10 Metanoia, Inc., 888 Villa Street, Suite 500, Mountain View, CA 94041, USA. © 2011 Metanoia, Inc.
  6. 6. are now under development to incorporate more complex modulation schemes such asQPSK and QAM, which are required to achieve 100Gbps per wavelength and higher andachieve aggregate capacities of 500Gbps or 1Tbps per PIC, and more than 10Tbps perfiber over long-haul networks.4.2 Packet-Optical Transport Systems (The New P-OTS!) -- Requirements,Architectures and Trade-OffsPacket-optical transport systems/platforms (P-OTS or P-OTP) are a new class ofnetworking platforms that combine the functions and features of SONET/SDH/OTNADMs or cross-connects, Ethernet switching and aggregation systems, andWDM/ROADM transport systems into either a single network element or a small set ofnetwork elements.The goal of a Packet-Optical Transport System is to combine the best features of all ofthe legacy technologies – such as SONET/SDH, IP, ATM, and Ethernet. As a result, therequirements can be thought of as drawing upon the features of each technology in thefollowing way:i) From SONET/SDH: Resilience -- 50 ms recovery, path provisioning, and OAM (veryimportant for the operator)ii) From ATM – Sophisticated Traffic Management and QoS as in ATM, includingtraffic engineering and guaranteed QoS.iii) From IP/Ethernet -- Very high efficiency from statistical multiplexing ofpackets/frames, and packet-flow control that are key for multimedia traffic.iv) Flexible grooming or the ability to efficiently map a rich service mix onto theunderlying transport layer by switching at the wavelength (lambda) level, sub-wavelength(ODU) level, port (TDM or SONET/SDH) level, and sub-port/packet (Ethernet, MPLS)level.P-OTS architectures may be divided into three broad types:i) IP-over-Glass or Layer 3 routers with integrated transponders connected to a DWDMsystem. These rely on the router to perform the switching function and eliminate O-E-Ointerfaces. Also, network architecture is simplified by eliminating SONET/SDH, thusreducing Capex and Opex. Understandably, many carriers are cautious about thisapproach because it burdens the Layer 3 IP routers with the additional responsibilities ofmonitoring and managing an agile wavelength infrastructure – functions normallyperformed by DWDM systems.ii) Carrier Ethernet Switch Routers with Connection-Oriented Ethernet (COE;controlled using PBB-TE or MPLS-TP) plus a DWDM layer. The goal here is to leverageA Metanoia, Inc. Technology Paper Page 6 of 10 Metanoia, Inc., 888 Villa Street, Suite 500, Mountain View, CA 94041, USA. © 2011 Metanoia, Inc.
  7. 7. the low cost points of Ethernet, while getting the advantage of its traffic management andtraffic engineering capabilities.iii) Packet-Optical devices combining SONET/SDH and IP/Ethernetswitching/aggregation with DWDM transport. They emphasize a modular architecture,where sub-wavelength multiplexing and packet switching are done and traffic is groomedonto DWDM transport. These systems permit router bypass of non-IP traffic (e.g. L2traffic, TDM traffic, and transit traffic), and minimize wavelength requirements byintegrating SONET/SDH, MPLS, and OTN switching onto a single system.The best alternative will depend on the existing and projected traffic mix (TDM to packetbalance in the operators network), existing capital investment in network assets(SONET/SDH ADMs, ROADMs, switches/routers), need for efficient utilization ofoptical resources (wavelengths), and the carriers operations model (i.e., whether theIP/MPLS and transport teams are separate or common). Packet Optical Transport System ArchitecturesOptical devices combining CESRs (Carrier-Ethernet Switch Layer 3 Routers with-- SONET/SDH Routers) with COE integrated transponders-- Ethernet swtiching/aggregation Combined with a separate WDM (IPoDWDM)-- WDM transport layer E.g. Cisco CRS-1, GSR 12000,E.g. Fujitsu Flashwave 9500 E.g. Tellabs 8800, Juniper 960 MX Juniper T-SeriesFigure 3 Packet-Optical Transport Systems (P-OTS): Architectures in usetoday4.3 Photonic Control-Plane Software: Advances and ChallengesThe data plane, comprising flexible ROADMs and packet-optical transport systems, mustbe complemented by a highly integrated management and control plane that spans thepacket, TDM, and optical domains. This control plane software is critical for future agileoptical networks, and is largely lacking in todays networks.The control plane, which uses routing and signaling to setup the connections betweennodes, coupled with an efficient management plane is essential to orchestrate theoperations of the data plane.Developments in the control plane are occurring within the IETF, which has developedthe GMPLS control plane that is now being refined to include wavelength switchedoptical network (WSON) requirements. This will allow the control plane to havesimplified knowledge of the optical parameters (such as chromatic dispersion andpolarization mode dispersion) and simple rules that can be used to decide whether anoptical path is adequate or requires signal regeneration.A Metanoia, Inc. Technology Paper Page 7 of 10 Metanoia, Inc., 888 Villa Street, Suite 500, Mountain View, CA 94041, USA. © 2011 Metanoia, Inc.
  8. 8. The ITU-T has developed control plane requirements and architecture, under theumbrella of ASON (Automatically Switched Optical Networks). The GMPLS/ASONcontrol plane comprises a common part and a technology-specific part to includetechnologies such as SONET/SDH, OTN, wavelengths, and MPLS-TP.By combiningelectrical and optical switching and an integrated control plane, the operators will be ableto continually optimize their networks, and devolve them to the lowest-cost and mostpower-efficient solutions. This approach can provide lowest TCO, the flexibility to adaptto any service mix, and provide carrier-class performance across the network.The User-to-Network Interface (UNI) and the External Network- to-Network Interface(E-NNI) implementations, based on the ITU-T, OIF and MEF standards could provevery useful for carriers. The UNI standards should enable operators to have packetswitching devices that can signal the agile optical network, and request wavelengthservices for certain duration over a specific path and with a defined level of protection.E-NNI implementations will enable Wavelength Networks to share topology andavailability information in a way to facilitate service deployment across multi-vendor(and possibly even multi-carrier networks) in an end-to-end manner. The (OIF) is onebody focused on facilitating trials and agreements in this area.5 Open Issues and Carrier ConcernsEven as advancements in packet-optical integration continue to be made, challengesremain before a fully agile optical network is a reality.An important consideration is providing the control plane with knowledge of the opticalimpairments, and enabling routing transparently between vendors. This is because it isvery difficult to identify all the optical parameters in a compact way to be used in aninter-vendor setting. Another challenge is inter-layer management, both across thedifferent layers (optical, TDM, and packets) and across diverse vendor gear.Similarly, handling increasing customer application rates, say 1, 10 or 40 Gb/s on 100Gb/s infrastructure, will require the use of OTN (G.709) multiplexing and electricalswitching, plus control plane support.Other important operator concerns include network management costs, which aresignificant. Thus, advanced management software that integrates with operator OSS/BSSsystems is key. Some operators, such as BT, have deployed dedicated devices forsurveillance and diagnostics, and have developed SDK’s or API’s that enable newequipment to “speak” to any component of their OSS systems, and simplifies softwaredevelopment that occurs as a result of introduction of new hardware platforms. Inaddition to investing in significant in-house OSS development efforts, operators,including Verizon, AT&T and Qwest, have frequently leveraged third-party certificationsor integrators like Telcordia’s OSMINE process to ensure that any potential vendorsolution will work with the carriers existing management systems.A Metanoia, Inc. Technology Paper Page 8 of 10 Metanoia, Inc., 888 Villa Street, Suite 500, Mountain View, CA 94041, USA. © 2011 Metanoia, Inc.
  9. 9. Finally, modularity of the system makes the challenge of integration for an operator mucheasier. This modularity comes in multiple forms--as universal switch fabrics and theability to mix-and-match linecards (from all TDM to all packets and everything inbetween), or as modularity of the associated software with the ability to selectively turnon or off specific features.6 References [1] Michael Kennedy, “Sizing-Up The Approaches,” Presentation, Network Strategy Partners, Fierce Telecom: Packet-Optical Networking Platforms Webinar, July 14, 2010. [2] Matt Rossi, “Enterprise Bandwidth Consumption,” Presentation, Zayo Enterprise Networks, Fierce Telecom: Making the 100 Gb/s Connection Webinar, July 21, 2010. [3] Internet Engineering Task Force IETF, “MPLS-TP Standard,” WikiPage,, Accessed 12/29/2010. [4] Steven Gringeri, Bert Basch, Vishnu Shukla et al, “Flexible Architectures for Optical Transport Nodes and Networks,” IEEE Comm. Mag., Vol. 48, Issue 9, July 2010, pp. 40-50. [5] Mark Allen, Chris Lou, Serge Melle, Vijay Vusirikala, “Digital Optical Networks Using Photonic Integrated Circuits Address the Challenge of Reconfigurable Optical Networks,” IEEE Comm. Mag. Vol. 44, Issue 12, Dec. 2007, pp. 2-11. ***********************************About Metanoia, Inc.Metanoia, Inc. is a niche Bay-area consultancy that, since 2001, has been helping players acrossthe full telecom ecosystem (chip and semiconductor vendors, system vendors, operators andcarriers, technology houses, and software/planning tool vendors) solve complex problems in thetelecom space. Our contributions have spanned the strategy for, and the analysis, design, andarchitecture of, systems, networks, and services, to the optimization of the equipment andnetworks deploying them.Our contributions have allowed a marquee list of client companies (ranging from fast-pacedinnovative startups and international leaders, to giants and technology leaders in the US Fortune1000) across 4 continents accelerate technology design and development or network design anddeployment, speed-up time-to-market, slash learning cycles, master complex technologies, andenhance customer-interaction and revenues, yielding benefits many times their investments inour services.In short, we have been Powering Leadership Through InnovationTM! To learn more about howwe can help you, please contact us at or at +1-888-641-0082, and wewill be delighted to collaborate on efficiently solving your problem, and enhancing savings andrevenue for you.A Metanoia, Inc. Technology Paper Page 9 of 10 Metanoia, Inc., 888 Villa Street, Suite 500, Mountain View, CA 94041, USA. © 2011 Metanoia, Inc.
  10. 10. About Infinera, Inc.Infinera (Nasdaq: INFN) provides Digital Optical Networking systems to telecommunicationscarriers worldwide, and counts itself among the world’s most innovative developers of opticalnetworking systems. Founded in 2001, Infinera developed the industrys first large-scale photonicintegrated circuit (PIC), which dramatically increases the performance of optical networking byputting 50 optical components on a single chip smaller than a human fingernail, and with tentimes the data rate of the lasers used in conventional optical systems.With one of the most successful technology IPOs of recent years, Infinera has developed andbrought to the market innovations at every level of optical system design. At a time when theInternet has entered an exciting new growth phase, Infinera gathered a broad array of skills andtalents and put them to work to deliver the future of optical networking. Lead by Infinerasfounders, all major figures in the optical systems and components business, Infinerasengineering team consists of more than 300 engineers in the U.S. and India, with expertise inphotonics, optical components, ASIC design, system design and software design.Its innovations have helped it win market share leadership among major US and global networks,accounting for more than 40% of the shipments of 10Gb/s long-haul DWDM ports worldwide,according to the DellOro Group.Infineras systems are unique in their use of a breakthrough semiconductor technology: thephotonic integrated circuit (PIC). Infineras systems and PIC technology are designed to providecustomers with simpler and more flexible engineering and operations, faster time-to-service, andthe ability to rapidly deliver differentiated services without reengineering their opticalinfrastructure. For more information, please visit Metanoia, Inc. Technology Paper Page 10 of 10 Metanoia, Inc., 888 Villa Street, Suite 500, Mountain View, CA 94041, USA. © 2011 Metanoia, Inc.