Illuminating Optical Ethernet Networks!


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The goal of the carrier today is to offer manageable end-user data services with a measurable QoS (Quality-of-Service) at the minimum cost per bit, using the smallest footprint systems, with the simplest implementation that allows for service-level agreements, operational efficiency, and traffic scalability. 

This has lead to the emergence of two design principles: the lower the layer at which...

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Illuminating Optical Ethernet Networks!

  1. 1. Illuminating Optical Ethernet Networks!Vishal Sharma, Ph.D., Principal Technologist & Consultant, Metanoia, Inc., Mountain View, CA 94041, USA. Shahram Davari, MASc, Associate Technical Director, Network Switching, Broadcom Corporation, 3151 Zanker Road, San Jose, CA 95134, USA. Table of Contents1.  Introduction: Evolution of Transport Networks and a Mélange of Terms............................... 2 2.  Versatile Packet Networking with Ethernet: Service, Transport Technology, and PHY ......... 2 3.  “Optical Ethernet Network” Defined ...................................................................................... 3 4.  “Carrier Ethernet” and Its Relation to Optical Ethernet ........................................................ 4 5.  Packet-Optical Transport (The New P-OTS!): What It Is and Where It Fits........................... 6 6.  Optical Ethernet Applications/Services in Use Today ............................................................. 7 7.  Service Provider Offerings Based on Optical Ethernet ........................................................... 8 8.  How It All Fits: A Recap and a Look Towards the Future....................................................... 8 A Metanoia, Inc. Technology Paper Page 1 of 10 Metanoia, Inc., 888 Villa Street, Suite 500, Mountain View, CA 94041, USA. © 2010 Metanoia, Inc.
  2. 2. 1. Introduction: Evolution of Transport Networks and a Mélange of TermsThe TDM-to-packet network transformation has been underway in transport/telecommunicationsnetworks for some years now, fueled primarily by two trends: (a) the advent of triple-play (voice,video, data) for enterprise and residential customers, and, lately, the explosion in video andmobile data services, and (b) the evolution in both packet- and transport-network equipment.The goal of the carrier, of course, is to offer manageable end-user data services with a measurableQoS (Quality-of-Service) at the minimum cost per bit, using the smallest footprint systems, withthe simplest implementation that allows for service-level agreements, operational efficiency, andtraffic scalability. This has lead to the emergence of two design principles: the lower the layer atwhich packet data is carried, the lower the cost, and fewer layers (simpler systems) mean lessexpensive systems, and, hence, lower cost. Thus, recent developments in both the Ethernet andoptical spheres have been geared towards this goal.In this regard, there have been rapid advancements to make packet technologies, such as IP andEthernet, more “circuit-like”, and to make transport technologies and equipment more dynamicand, thus, “packet friendly.” These developments have lead, over the last few years, to theemergence of a mélange of terms: “optical Ethernet”, “metro optical Ethernet”, “packet-opticaltransport”, “Carrier Ethernet”, “metro Ethernet”, which are often used interchangeably, blurringthe distinction between them, and leading to confusion in industry circles. Our objective in thisarticle is to define the terms: optical Ethernet, Carrier Ethernet, and packet-optical transport,explain their relationships, and show how they all fit together in emerging optical Ethernetnetworks.2. Versatile Packet Networking with Ethernet: Service, Transport Technology, and PHYBefore defining the term “optical Ethernet,” it is useful to point out that the term “Ethernet” itselfcan apply to any one of the three roles of Ethernet technology: as a service, as a transporttechnology, and as a PHY layer (cf. Figure 1).A Metanoia, Inc. Technology Paper Page 2 of 10 Metanoia, Inc., 888 Villa Street, Suite 500, Mountain View, CA 94041, USA. © 2010 Metanoia, Inc.
  3. 3. Figure 1 Three key components of Optical Ethernet: service, transport, PHY, together with the technologies and standards organizations involved in specifying/developing each componentAn Ethernet service is offered to the end-customer (the enterprise or residential customer), runsend-to-end (customer premise-to-customer premise) and is one in which the traffic flow into/outof the system at the customer consists of Ethernet frames. An Ethernet service is thus the Ethernetconnectivity between customer equipment.A carrier-grade Ethernet service is one that is scalable (to many MAC addresses and end points),offers QoS (traffic management), reliability (protection), and manageability (OAM andmonitoring), and can span long distances (of MAN/WAN scope; typically 10s to 1000s ofkilometers).Ethernet transport refers to the ability to switch/route Ethernet frames (belonging to an Ethernetservice) between network nodes, by setting up/using connection-oriented, traffic engineered pathsin the network with deterministic performance (QoS, delay, jitter, loss, reliability). In otherwords, Ethernet transport refers to the setting up of the “pipe” through which the Ethernet framestravel, and to determining its routing within the cloud.Ethernet transport makes it possible to realize connection-oriented Ethernet (COE). COE, inessence, refers to the collection of control-plane protocols and data-plane settings that create aconnection-oriented capability for transferring the frames of an Ethernet service. We mention thatEthernet transport could be provided either by enhancing Ethernet technology (e.g. as is done inProvider Backbone Bridging with Traffic Engineering, PBB-TE, in the IEEE 802.1Qay standard)or by a different technology (e.g. using MPLS-TP technology being developed jointly by theIETF & the ITU-T). Both of these forms of transport involve switching/routing data frames, andare, therefore, referred to as Layer 2 (or L2) transport.It is also possible to embed Ethernet frames in a different transport networking layer, such as theone provided by the ITU-T’s G.709 OTN (Optical Transport Network) standard. This form oftransport involves switching/routing traffic at the optical channel data unit (ODU) level and istherefore referred to as Layer 1 (or L1) transport.Ethernet PHY refers to the framing and timing of the actual bits of the Ethernet frame, and theirtransmission over a physical medium – copper wire, coaxial cable, or optical fiber – to connectswitches at the physical layer. Some common Ethernet PHYs are the 1 GE (IEEE 802.3z), 10 GE(IEEE 802.1ae), and 100 GE (IEEE 802.3ba) Ethernet PHYs. Note that Ethernet frames can alsobe embedded in other PHY framing standards, such as those in the ITU-T’s G.709 OTN (OpticalTransport Network) standard.3. “Optical Ethernet Network” DefinedWith this background, we may now define an Optical Ethernet Network as a network spanning aMAN/WAN that offers a carrier-grade Ethernet service, running over a connection-orientedA Metanoia, Inc. Technology Paper Page 3 of 10 Metanoia, Inc., 888 Villa Street, Suite 500, Mountain View, CA 94041, USA. © 2010 Metanoia, Inc.
  4. 4. Ethernet (COE) transport infrastructure over an optical PHY (cf. Figure 2). The optical PHYcould be provided either by the OTN’s optical channel (OCh), or by an Ethernet PHY runningover optics, and may be multiplexed onto a given fiber using CWDM/DWDM technology.Figure 2 Relationships of the different layers: service layer, transport layer, and PHY layer, and their corresponding entitiesA key characteristic of optical Ethernet is that its scope is beyond the enterprise LAN, and spans ametropolitan-area or wide-area network.4. “Carrier Ethernet” and Its Relation to Optical EthernetThe term “Carrier Ethernet” was formalized by the work of the MEF (Metro Ethernet Forum) inthe 2004-2005 time frame, which defines Carrier Ethernet as “a ubiquitous carrier-grade Ethernetservice, which has the following five attributes: standardized services, scalability,reliability/protection, hard QoS, and service management.” The technical work of the MEF (asdescribed in its specifications) together with the technical work of associated standards bodies(ITU-T, IEEE, IETF) together enable the functionality and attributes of Carrier Ethernet. • Standardized services refers to having a uniformly accepted definition of core services that serve as the building block for applications running atop them (more on these below). • Scalability refers to a service that scales to millions of UNIs (end-points) and MAC addresses, spanning access, local, national, and global networks, with the ability to support a wide bandwidth granularity and versatile QoS options. • Reliability refers to the ability to detect and recover from errors/faults without impacting customers, typically with rapid recovery times, as low as 50ms.A Metanoia, Inc. Technology Paper Page 4 of 10 Metanoia, Inc., 888 Villa Street, Suite 500, Mountain View, CA 94041, USA. © 2010 Metanoia, Inc.
  5. 5. • Hard QoS implies providing end-to-end performance based on rates, frame loss, delay, and delay variation, and the ability to deliver SLAs that guarantee performance that matches the requirements of voice, video, and data traffic over heterogeneous converged networks. • Service management implies having carrier-class OAM, and standards-based, vendor- independent implementations to monitor, diagnose, and manage networks offering Carrier Ethernet service.The services defined by the MEF are in terms of an Ethernet Virtual Connection (EVC), which isdefined as an association of two or more User Network Interfaces (UNIs) at the edge of a metroEthernet network (MEN 1 ) cloud (i.e. subscriber sites), where the exchange of Ethernet serviceframes is limited to the UNI’s in the EVC. The MEF defines 3 standardized services: E-Line (apoint-to-point EVC), E-LAN (a multipoint-to-multipoint EVC), and E-Tree (a point-to-multipoint“rooted” EVC, where the root(s) can communicate with any of the leaves, but the leaves mustcommunicate with each other only via the root). Thus, an Ethernet Private Line service is builtusing a point-to-point EVCs, while an Ethernet Private LAN service is built using mp2mp EVCs.1 Even though the MEF specifications refer to MENs (metro Ethernet networks) this is now a generic termthat refers to the Carrier-Ethernet service enabled network, which can span a variety of access, metro, andlong-haul networks.A Metanoia, Inc. Technology Paper Page 5 of 10 Metanoia, Inc., 888 Villa Street, Suite 500, Mountain View, CA 94041, USA. © 2010 Metanoia, Inc.
  6. 6. Figure 3 Optical Ethernet Network with the service, transport and PHY components in operationThus, we see that Carrier Ethernet comprises the service component of optical Ethernet networks(cf. Figure 1, Figure 2, and Figure 5).5. Packet-Optical Transport (The New P-OTS!): What It Is and Where It FitsPacket-optical transport systems (P-OTS or P-OTP) are a new class of networking platforms thatcombine the functions and features of SONET/SDH/OTN ADMs or cross-connects, Ethernetswitching and aggregation systems, and WDM/ROADM transport systems into a single networkelement, thus providing “data-aware optical networking.”A P-OTS network element typically will have ITU-T G.709 OTN support, a COE component,and support for WDM. These elements also offer transport of a wide range of client signals –Ethernet (dominant), legacy SONET/SDH, SAN traffic, IP/ATM, video traffic, and can switch atthe wavelength level (WDM), sub-wavelength (or ODU) level, TDM level (SONET/SDH), andA Metanoia, Inc. Technology Paper Page 6 of 10 Metanoia, Inc., 888 Villa Street, Suite 500, Mountain View, CA 94041, USA. © 2010 Metanoia, Inc.
  7. 7. packet level (Ethernet, MPLS). A P-OTS network element enables a carrier, especially in theMAN/WAN, to quickly and cost-effectively change connectivity and bandwidth in the network,without knowing about the actual services.Key architectural features of P-OTS elements are: • Universal switching architecture/fabric for switching traffic at different layers (OTN, TDM and packet) • Ability to switch, groom, and manage traffic in its native format (i.e. SONET/SDH traffic as TDM traffic, and IP or Ethernet traffic as packet traffic), thus, allowing for the percentage of each traffic type to vary dynamically (all Ethernet to all SONET/SDH and anything in between, for instance) • Software-selectable ports that can switch between switching SONET/SDH to switching Ethernet, depending on the trafficEven as this definition is gaining industry consensus, according to research firm Heavy Reading,there are three architectures that are currently deemed to fall under the packet optical transportumbrella, shown in Figure 4.Figure 4 Packet-Optical Transport Systems (P-OTS): Architectures in use todayAs a result, a number of vendor products fall in this umbrella e.g. Alcatel-Lucent 1850 TSS,Ciena CN 4200 RS, Fujitsu Flashwave 9500, Meriton 7200 OSP, Tellabs 8800, 6300 & 7100Nano, Cisco 15454 and 7600 (with appropriate blades), Nortel OME 6500, Juniper 9600, and soon.Thus, P-OTS platforms provide the transport and PHY components of optical Ethernet networks(cf. Figure 5).6. Optical Ethernet Applications/Services in Use TodaySo which applications/services is optical Ethernet being used for (or envisaged for) today?As expected, it is the business or residential services with triple-play applications(voice, video, and data to the desktop), mobile backhaul applications (where the Ethernet PHY isused between the base-station and the first switching node, and regular optical Ethernet networksA Metanoia, Inc. Technology Paper Page 7 of 10 Metanoia, Inc., 888 Villa Street, Suite 500, Mountain View, CA 94041, USA. © 2010 Metanoia, Inc.
  8. 8. are used in the backhaul and backbone networks), and utility infrastructure networks (where oil,gas, water, and electric utilities are transforming their aged communication systems into “data-aware” systems that allow for automation of functions such as billing, monitoring, meter reading).Applications such as software-as-a-service, VoIP, VoD, and hosted unified communications aredriving demand, as are ICT trends such as virtualization, data center outsourcing, data replication,disaster recovery, remote backup, and IT outsourcing.From a Chip/SoC perspective, several vendors offer solutions for Optical Ethernet transport andPHY, such as Broadcom’s XGS (BCM56000 series), EZChip’s NP series, Xelerated’s X seriesand T-PACK’s TPX series. These products can offer Ethernet and Connection Oriented Ethernet(COE) switching, plus (in many cases) an integrated Ethernet PHY.In addition, there are vendors that offer OTN transport and switching products: e.g. Broadcom(BM8512), AMCC (Pemaquid), Cortina Systems (IXF30000 series) and T-PACK (P-OKETseries). These products typically map Ethernet to OTN, and some even provide OTN (ODU-level) switching.7. Service Provider Offerings Based on Optical EthernetService providers worldwide (North America, Europe, EMEA) are rapidly moving to Ethernetservices. As of June 2009, Current Analysis research showed that metro (MAN) Ethernet circuitsconstitute the bulk of (over 75%) optical Ethernet offerings, with p2p more common thanmp2mp.The shift in deployment clearly favors fiber (FTTx: Fiber-to-the building, curb, or home), aswould be expected for optical Ethernet. A vast majority of US Ethernet is fiber-based, although inEurope, providers are deploying EoCopper for the “last mile.” Finally, cable MSOs offer Ethernetover HFC (hybrid fiber coax).In the US, Verizon and AT&T are leaders, offering E-LAN, E-Line, and VPLS services, withQoS, availability, regional/national/international coverage. In Europe, COLT is the leaderoffering COLT LanLink and COLT Ethernet VPN service (E-LAN), while KPN offers a VPLSservice in 22 nations. In APAC, Sing-Tel and TataComms both offer E-Line and E-LAN services,with SLAs, reachability, and broad coverage. In Middle East and Asia, Reliance Globalcom andReliance Communications are leaders, offering a VPLS-based optical Ethernet service.8. How It All Fits: A Recap and a Look Towards the FutureThus, we see that in the trio: service, transport and PHY, that are the components of opticalEthernet: Carrier Ethernet provides the service component, packet-optical transport gear providesthe transport and PHY component, and the various IETF, IEEE, and ITU-T standards provide thespecifications for the PHY layers, as well as connection-oriented Ethernet (cf. Figure 5).A Metanoia, Inc. Technology Paper Page 8 of 10 Metanoia, Inc., 888 Villa Street, Suite 500, Mountain View, CA 94041, USA. © 2010 Metanoia, Inc.
  9. 9. Figure 5 Optical Ethernet: How it all fitsAs optical Ethernet evolves over the next few years, there will be further reduction in the layersleading to a fused Ethernet-WDM packet transport layer with circuit-like capabilities, and topacket-optical systems optimized for it. This allows the providers to handle increasing volume ofdata traffic, while reducing the number of network elements by using Ethernet as the commonpacket technology in access, aggregation and core networks. ***********************************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.About Broadcom, Inc.A Metanoia, Inc. Technology Paper Page 9 of 10 Metanoia, Inc., 888 Villa Street, Suite 500, Mountain View, CA 94041, USA. © 2010 Metanoia, Inc.
  10. 10. Broadcom Corporation is a major technology innovator and global leader in semiconductors forwired and wireless communications. Broadcom(R) products enable the delivery of voice, video,data and multimedia to and throughout the home, the office and the mobile environment. Weprovide the industrys broadest portfolio of state-of-the-art system-on-a-chip and softwaresolutions to manufacturers of computing and networking equipment, digital entertainment andbroadband access products, and mobile devices. These solutions support our core mission:Connecting everything(R).Broadcom, one of the worlds largest fabless communications semiconductor companies, with2009 revenue of $4.49 billion, holds more than 3,800 U.S. and 1,550 foreign patents, and hasmore than 7,800 additional pending patent applications, and one of the broadest intellectualproperty portfolios addressing both wired and wireless transmission of voice, video, data andmultimedia.A FORTUNE 500(R) company, Broadcom is headquartered in Irvine, Calif., and has offices andresearch facilities in North America, Asia and Europe. Broadcom may be contacted at+1.949.926.5000 or at Metanoia, Inc. Technology Paper Page 10 of 10 Metanoia, Inc., 888 Villa Street, Suite 500, Mountain View, CA 94041, USA. © 2010 Metanoia, Inc.