omlt for dummies

7/27/2019 OMLT for Dummies

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OMLTFOR

DUMmIES

ECI TELECOM SPECIAL EDITION

by Pat Hurley



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OMLT For Dummies, ECI Telecom Special Edition

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Contents at a Glance

I n t r o d u c t i o n 1

Chapter 1: The Evolution of Transport Networks 5

Chapter 2: Introducing the OMLT 11

Chapter 3: Digging Into Carrier Ethernet 15

Chapter 4: Moving to the OpticalTransport Network 23

Chapter 5: Understanding the Role of WDM 29

Chapter 6: Ten Reasons for Evolving to OMLT 39

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Introduction

Telecommunications service providers have a new optionwhen it comes to how they build and expand their

networks as they work to complete the transition to all-packet networks and meet today and tomorrows bandwidth

demands. For the past few years Packet-Optical TransportSystems (P-OTS) have been the leading contender for thistransition, providing an integrated solution to support packettransport over optical networks as well as preparing networksfor advanced services supported by Multiprotocol LabelSwitching (MPLS) and Carrier Ethernet.

But P-OTS doesnt provide all the integration that carriers arelooking for, because most solutions were built on previous-

generation architectures. Luckily a new network approach Optimized Multi-Layer Transport (OMLT) systems hasbecome available. The OMLT brings a highly-integrated andmodular approach to packet optical networking, incorporat-ing multiple network technology layers into a single deviceand using a single network management system to control itall. The result is reduced capital and operating expenses anda network built to support yesterdays (legacy), todays, andtomorrows services.

About This BookOMLT For Dummies, ECI Telecom Special Edition, walks youthrough the concept of the OMLT systems, digs into its com-ponent technologies, and explains why the OMLT can fit intoyour network. The book isntwritten for telecom engineerslooking for deep technical knowledge or tips for planning net-

work build-outs. Instead, youll find that this book is designedfor the non-technical folks marketers, sales professionals,finance wizards, and so on involved in the telecommunica-tions industry who need to understand the trends in the carriernetwork and what solutions enable their company to meet thechallenges of tomorrows network and to succeed (in terms ofprofitability and customer satisfaction) while doing so.



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OMLT For Dummies, ECI Telecom Special Edition2

How This Book Is OrganizedThis book is organized into six chapters. As is the case in anyFor Dummies book, each of these chapters is self-contained,so you dont need to read the book linearly if you see achapter that you already know everything about, feel freeto skip it. Whenever a complex topic from another chapteris raised, you see a reference to that chapter no need tospend your time digging around in the table of contents.

Chapter 1: The Evolutionof Transport NetworksChapter 1 provides an overview of transport networks andhow they evolved as the services running over them haveevolved. In this chapter, you first look at the building blocksof transport networks, including TDM cross connects,SDH/Sonet, the Optical Transport Network (OTN), CarrierEthernet Switch Routers (CESR), and Wavelength DivisionMultiplexing (WDM). Following this, you discover current car-rier approaches to implementing these technologies, best-of-breed, and P-OTS. You also find out more information aboutthe issues that carriers are finding with P-OTS, and why a newconcept the OMLT has been introduced.

Chapter 2: Introducing the OMLTChapter 2 gives you details on the new networking conceptthat underlies this book the OMLT. In this chapter, youlook at the network requirements that have driven carriers tosomething beyond P-OTS, and discover how the OMLT meetsthose needs to a T. Finally, youll dig into some of the piecesand parts (and functionalities) that make the integrated OMLTsolution what it is.

Chapter 3: Digging IntoCarrier EthernetChapter 3 examines Carrier Ethernet and talks about CarrierEthernet Switch Routers, and then digs into MPLS. It finishes upwith discussions of MPLS variants MPLS-TP and IP/MPLS.



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Introduction 3

Chapter 4: Moving to the Optical

Transport NetworkCarrier networks have long relied on Sonet/SDH optical net-working technologies. Sonet/SDH is a reliable system that tele-com engineers know like the back of their hands, but it wasbuilt for voice networking and is beginning to show its age. Anewer transport layer called the Optical Transport Network(OTN) has been developed as Sonet/SDHs replacement. Inthis chapter, you discover OTN in general, find out the rea-

sons why carriers need OTN, and examine the main functionsof the OTN. The end of this chapter shows you the vital role ofthe ODU (Optical Data Unit) cross connect in the OTN.

Chapter 5: Understandingthe Role of WDMChapter 5 gives you the skinny on a technology that greatlyexpands the capacity of the fiber youve already got in placein your network: wavelength division multiplexing. I discussthe reasons carriers need WDM (hint: more bandwidth!). ThenI talk about the major variants of WDM, coarse and dense(CWDM and DWDM, respectively). You find out the equip-ment needed to provide WDM in your network, includingmultiplexers and optical add-drop multiplexers, paying spe-cial attention to ROADMs, or reconfigurable optical add-drop

multiplexer). Finally, I talk about the move from 10 Gbps to 40and 100 Gbps channels.

Chapter 6: Ten Reasons forEvolving to the OMLTSometimes you just need a quick answer. Chapter 6 provides

just that with a bunch of compelling reasons why the OMLTmakes sense for carriers. Look here if you want a good quickoverview of why the OMLT is so important to the future ofyour network or whenever you just need a quick reminder.



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Icons Used in This BookThis book calls out important bits of information with iconson the left margins of the page. Youll find these icons in thebook:

The Tip icon points out a bit of information that aids in yourunderstanding of a topic or provides a little bit of extra infor-mation that perhaps isnt 100 percent necessary but whichmay broaden your understanding of what youve just read.

The Remember icon points out information that you shouldlock away in your memory because you just may need toknow it again in the future.

I try to keep the hardcore techie stuff to a bare minimum. Youdont need to know these factoids to get the most out of thebook, but they may come in handy.



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Chapter 1

The Evolution of TransportNetworks

In This Chapter Understanding transport network fundamentals

Getting to know CESRs and WDM

Remembering P-OTS

Transport networks are the basis of all telecommunicationsservices. These networks long ago moved from being

primarily voice networks used for public switched telephonenetwork (PSTN) voice calls from and to landlines only, towardincorporating mobile elements (like 3 and 4G mobile phonenetworks), data (including leased line services and Internetservices) and even video services (watched any YouTubevideos lately or even an on-demand movie? they were

brought to your computer or mobile device via a transportnetwork). The transport network is, to most users, unseenand relatively unheralded, but it truly is the engine that keepsthe entire connected world running.

Telecommunications providers are finding that their trans-port networks have to cope with increasing demands formore capacity, bandwidth, services and applications. So inthis chapter, you take a look at some of the basic technolo-

gies and components that underlie transport networks, lookat how these networks have evolved over the past few years,and examine a new approach the Optimized MultilayerTransport Platform (OMLT). I show how this approach pro-vides true integration in supporting all the different networkelements and can decrease a telecommunication carriers



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costs and reduce operational complexity. Those facts canlead to a more profitable, sustainable, and successful busi-

ness model.

Understanding TransportBasic Functions

Transport network elements carry out two main functions

albeit in a number of different ways, depending on the make-up of the network. These functions are

Transmit and receive electronic or optical telecommuni-cations signals (data, voice, and video) between differentlocations

Switch those signals so they take the right path and getto the desired destination, in the most cost-effective way

Over many decades of development a number of deviceshave been installed in carrier networks to carry out thesefunctions.

TDM cross connectsTime Division Multiplexing(TDM) is a legacy telecommunica-tions protocol designed around the concept of circuits in the

network. A circuit is a line or conduit that transports informa-tion (voice, video, data, and so on) between one point andanother. When a circuit is set up (be it permanent or tempo-rary), a portion of the overall telecommunications network issolely dedicated to that particular stream of communications.

TDM cross connects have two primary types:

Digital cross connects designed for legacy non-optical

TDM circuits, like T1 and E1(T1 is a standard circuit inthe US, while E1 is the analogue found in the rest of theworld)

Optical cross connects designed to carry optical signalsover fiber, rather than electrical signals over copper



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TDM cross connects dont switch packets, they switch circuits.Therefore, theyre designed for aggregating more persistent

circuit connections (like legacy T1 and E1 data connections),which typically stay in place for days, weeks, or months,instead of moving packets around to varying locations on anindividual, packet-by-packet basis. Theyre a legacy circuit-switched network technology and, as such, are part of todayspacket networks only so far as they support legacy services.Ideally, packet switching technologies transparently (to theend-users) can carry these legacy TDM circuits without requir-ing traditional cross-connect equipment in the network.

SDH/SonetThe most common TDM network in use in carrier networks used both in their metro area networks serving a city or met-ropolitan district and in their core networks carrying trafficamong cities is Sonet/SDH (Synchronous Digital Hierarchy).Sonet and SDH are essentially the same thing a standard

system for multiplexing (or combining multiple data signals)over an optical network. Sonet is the system used in the U.S.and Canada, while most of the rest of the world uses SDH. Forthe purposes of this book, you can think of Sonet and SDH asbeing the same thing.

Making the shift to opticaltransport networks

As bandwidth demands haveincreased driven by vastlyincreased data service demands,huge growth in video services, andthe mobile data revolution carriershave found that they needed some-thing more than Sonet/SDH in theirtransport networks. This led to a newapproach a successor to Sonet/SDH called Optical TransportNetworks (OTN). OTN combines theunderpinnings of Sonet/SDH withWave Division Multiplexing (WDM).

A series of ITU (InternationalTelecommunications Union) recom-mendations defines the technicalcharacteristics of the OTN. Thesestandards range in speed from a bitless than 3 gigabits (Gbps) all theway up to over 100 Gbps, and aredesigned to carry both standardvariants of Sonet/SDH and Ethernetsignals all the way up to 100 GbpsEthernet.



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WDM: Wave Division MultiplexingCarriers face a constant need to provide more bandwidth totheir customers preferably without needing to spend a lotof money digging new trenches and installing more fiber in thenetworks outside plant. In an optical fiber network, you cantake a few different approaches for providing more bandwidthin your network:

Carry the signal over multiple individual fibers at a time(multiplexing the signal over separate strands)

Increase the electrical speed of the fiber by improvingthe transmitter so it can send more data over the fiber atonce essentially improving the lasers so they can sendsignals faster

Increase the number of signals that are transmitted overa single fiber by dividing them into different wavelengths(or colors), through a process known as wave divisionmultiplexing(WDM)

Equipment vendors have been combining the two latterapproaches better lasers and WDM (in particular, a variantof WDM known asDense WDMor DWDM) to vastly increasethe speed of fiber networks. Today, 10 Gpbs connections arecommon, and theyre rapidly giving way to 40 and 100 Gbpsconnections.

CESR: Carrier Ethernetswitches and routers

Carrier Ethernet is designed to leverage the flexibility and low-cost characteristics of Ethernet as well as Ethernets ubiquityin corporate, campus, and even home networks to providewide area network (WAN) Ethernet services to carrier customers.With Carrier Ethernet, a service provider can offer telecommu-

nications services that look and work like the Ethernet alreadyinside their customers networks. For example, with CarrierEthernet, a carrier can offer a business a LAN service connectingmultiple offices that provides access to all branches and remoteoffices as if they were directly attached to the home office LAN.

The devices that provide this service are Carrier EthernetSwitch Routers (CESRs). I talk more about them in Chapter 3.



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Deciphering Current MarketApproaches and Trends

As carriers try to create their next-generation networks, theytend to take one of two approaches.

Best of breedIn the best-of-breed approach, carriers find individualsolutions for each individual part of their network. Thesesolutions offer the best match of capacity, capability, andfeatures. The end result of such an approach tends to begood performance, which is great, but performance comes ata fairly high cost in complexity and price. Carriers find theyhave more elements within the network to manage, and eachof those elements have their own discrete management andconfiguration systems.

Integrated solution (Packet OTS)An integrated approach deploys a suite of transport tech-nologies known asPacket Optical Transport System (P-OTS).Specifically, P-OTS solutions incorporate into a single deviceor chassis (which creates more of a one-size-fits-all approachto building out network capacity) at least some of the follow-

ing devices:

WDM transport equipment and ROADMs (ReconfigurableOptical Add Drop Multiplexers, discussed in Chapter 5)

Sonet/SDH ADMs, or Add Drop Multiplexers, whichcombine (or multiplex) several lower bandwidth datastreams onto one higher bandwidth light path

CESRs

The goal of P-OTS is to combine the best of next generationoptics, including DWDM; support for Sonet/SDH networks; andthe advanced services offered by Carrier Ethernet.



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So, Whats the Problemwith P-OTS?

Over the past several years, many carriers have begun exam-ining and in some cases deploying P-OTS. These systemsare a good first effort, promising to integrate several of thepreviously disparate packet network elements into a singlechassis or device, often with a common management system.

Sounds great, right? Right. But some shortcomings to P-OTSexist as it is today:

Most P-OTS solutions provide some of the network ele-ments, but not all of them.

Most P-OTS solutions dont provide a true single manage-ment system, leaving carriers to pay for, train for, andmanage multiple systems often requiring differenttypes of engineering expertise.

Most P-OTS systems still require a separate, standaloneCESR installed adjacent to the P-OTS device to providefor advanced services effectively eliminating the pri-mary claimed benefit of P-OTS.

Most P-OTS solutions require a big, upfront investmentinstead of a pay-as-you-go approach. So a carrier wishingto migrate to P-OTS but needing to add or upgrade firston a single part of their overall network ends up payingfor more than it needs upfront.

Most carriers hate doing this, so they just dont upgrade at least not to P-OTS.

Clearly, a better solution is needed. One that truly fulfills thepromises of P-OTS. Thats where the OMLT comes into play.Check out Chapter 2 for more information on the OMLT.



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Chapter 2

Introducing the OMLTIn This Chapter Understanding how the OMLT works

Utilizing the OMLT as the better solution

Carriers have been, for several years, evolving their net-works in some very significant ways in order to meet

growing demand from their customers and to further theirmove to all-packet networks. At the same time, due to compe-

tition and broader economic trends, most carriers are underincreasing pressure to reduce their costs by both decreasingthe amount they spend on capital expenditures and by reduc-ing ongoing operations costs.

A recent approach toward this kind of packet and opticalupgrade to the network has been the P-OTS (packet opticaltransport systems) class of products, which combines ele-ments of carrier Ethernet, DWDM, and optical transport into

converged devices. Converging multiple functions into asingle device as opposed to installing individual devicesfor each function makes for, simply put, a cheaper andless complicated network, without too much compromise infunctionality.

Unfortunately, many P-OTS solutions fell short of this ideal,lacking either in integration or in functionality. Specifically,P-OTS solutions typically dont offer the higher level network

intelligence provided by a Carrier Ethernet Switch Router(CESR, discussed in Chapter 3).

Clearly something more was needed in order for carriersto reach the next level of high-bandwidth, high-quality con-verged networks. And thats where the OMLT comes in.



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Riding to the Rescue: OMLTOptimized Multi-layer Transport, or OMLT (you can call itomelet, if that helps you remember the acronym), is designedto overcome the shortcomings and fulfill the promise ofP-OTS. This new approach to networking is designed to pro-vide needed network flexibility and scalability while alsoreducing costs.

OMLT products incorporate DWDM, Carrier Ethernet with

MPLS (IP/MPLS and MPLS-TP), and OTN all into a highly mod-ular system designed to

Integrate packet and optical technology in a single platform

Minimize the total cost of ownership (TCO) of the network

Maximize network resources

Integrate with IP/MPLS core networks

Meet customers bandwidth demands, now and in thefuture

Keep costs down, both at the time of purchase andthroughout its operational lifespan

Provide the flexibility that enables a carrier to quicklyand competitively provide the services customers need,when they need them

OMLT is a suite of transport platforms that are deployedin the access network through the metro edge and ontothe metro core. OMLT is designed to provide a singleplatform that supports changing mix of packet-, circuit-,and wavelength-based services.



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Chapter 2: Introducing the OMLT 13

Understanding OMLTsPieces and Parts

OMLT is built on a modular architecture engineered to sup-port a build-as-you go approach. What I mean by that is thatwhile OMLT can support functionality like optical transport(OTN) and Carrier Ethernet (CESR), no requirement existsto install and configure all this possible functionality fromday one.

OMLT equipment can be easily configured (and re-configured)for a wide range of services through the addition of service-specific I/O (Input/Output) or service cards. The underlyingplatform architecture includes

An OS (Operating System) component that handles OAM(Operations, Administration and Management) and con-trol plane duties

A universal fabric (the underlying switching backbone ofthe device) that can support any service supported bythe device.

This feature means that portions of the OMLT chassiswont be stranded (or left unutilized) as different mixesof services are implemented.

Universal service card slots which can incorporate

Photoniccomponents,whichincludeROADMandWDM functionality, as well as optical amplifiers

SlotsforLayer2andLayer3I/Ocards(seeChapter3for more information about the OSI 7 Layer model)

An integrated management system that allows a carrier toleverage a single, familiar interface into network manage-ment, provisioning, troubleshooting, and maintenance



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This architecture provides a high degree of flexibility, so anychassis installed in a carriers network can be initially con-

figured for one service (say, wavelength services to an enter-prise campus) and easily be upgraded to incorporate otherservices (like Carrier Ethernet for mobile backhaul to nearbycell towers) with the addition of appropriate service cards.



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Chapter 3

Digging Into CarrierEthernet

In This Chapter Learning more about Carrier Ethernet Switches and Routers

Labeling your traffic with MPLS

Specializing MPLS for transport with MPLS-TP

Getting into IP-MPLS

Carriers are faced with an interesting set of challengeswhen they look to grow their networks. First, theyre

faced with ever-increasing bandwidth requirements becausebandwidth is required to support both traditional servicesand emerging ones like mobile backhaul, video, and cloudcomputing services. Second, they need to maintain the abilityto support their legacy TDM services until such services have

been completely replaced by equivalent packet services. Third,they face an ever increasing mix of services, each with its ownunique set of performance and reliability requirements.

Thats a big enough set of challenges all on its own, but car-riers must do all this while trying to minimize their capitalexpenses (Capex) and operating expenses (Opex). And theymust do this in the face of a competitive market that drivesdown prices and requires them to differentiate their offerings

in order to attract new customers.



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Its not an easy task by any means but the tool that mostcarriers are turning to is Carrier Ethernet. Carrier Ethernet

combines the low cost/high performance characteristics of allEthernet networks the sheer scope of the Ethernet marketmeans that the volume of components and equipment bringefficiencies of scale to the Carrier Ethernet market too withthe network reliability and resilience of traditional networktransport technologies like Sonet/SDH.

In this chapter, you discover the details of the devices thatenable Carrier Ethernet the Carrier Ethernet Switch

Router and then about the underlying network protocols MPLS that make it all work.

Understanding Carrier EthernetServices and Equipment

Carrier Ethernet has its roots inMetro Ethernet, a servicedesigned to provide native Ethernet services to businessesconnected to a metro optical network. The concept is prettysimple: business networks, networking equipment, and in-house networking expertise are all based on Ethernet, sowhy not offer these businesses a wide area network (WAN)service that is also based upon Ethernet. While its not assimple as just plug and play, Metro Ethernet and CarrierEthernet is designed to provide a familiar and compatible

replacement for the old leased lines that businesses used touse for the WAN access.

In the simplest term, Carrier Ethernet is the extension of thesemetro-area services into the core of the carrier network.

With Carrier Ethernet, a carrier can offer a range of differentservices to customers including

Virtual Private Network (VPN) services, which mimicdedicated point-to-point private line services over theshared infrastructure of Ethernet

Internet services, including IP-VPN



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Intranet-style Local Area Network (LAN) services, whichconnect multiple business locations as if they were all

sharing a common physical LAN in a single location(called Transparent LAN services)

Specialized services like mobile backhaul, connectingmobile towers to service provider core networks

All these services are delivered by using common and stan-dardized Ethernet interfaces at common Ethernet speedslike Gigabit Ethernet or 10 Gig Ethernet, so they connectnatively to the customers internal LAN.

The device that provides the control and traffic routing fora Carrier Ethernet network is the Carrier Ethernet SwitchRouter (CESR). A CESR is designed to provide the networkintelligence (switch and routing) to ensure that Ethernet pack-ets on the network are

Delivered to the right place at the right time

Kept secure on a shared medium (via use of VPNs)

Provide appropriate levels of throughput, latency, andother performance parameters

Meet a carriers service level agreements (SLAs)

Carried over appropriate routes based on traffic patternsand the physical network on which the traffic is carried

An important thing to remember about Carrier EthernetRouter Switches is that they do nothandle the opticaltransport duties (which we discuss in Chapter 4 on OpticalTransport Networks) of the network, like maximizing fibercapacity and utilization. Instead, separate devices arerequired for that part of the network meaning carriers willneed to buy, install, configure, and maintain two adjacent setsof equipment to provide Carrier Ethernet services.

Thats what makes OMLT solutions so compelling: Theyrethe first carrier transport solution to truly integrate boththe CESR and Optical Transport Network functionality into asingle device, with a common management system.



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What is MPLS?Carrier Ethernet services can be supplied directly over aSonet/SDH network, but most carriers use Multiprotocol LabelSwitching (MPLS). MPLS is a protocol designed to efficientlycarry multiple types of traffic over a single unified networkinfrastructure while fulfilling each traffic types specific per-formance and delivery priority requirements. MPLS labelsprovide simplified and faster routing than traditional routers.

MPLS has the following benefits:

Flexible bandwidth allocation bandwidth can be allo-cated on the fly based on service requirements

Security through IP tunnels across a network, withoutrequiring encryption on the ends of the network

Protocol independence MPLS can carry IP traffic,ATM, and so on all over the same infrastructure

Fast routing through the use of the labels described inthe protocols name

MPLS labels contain information about each packet, sothe router doesnt need to look inside each packet (asis done in traditional routing) to figure out what kind ofpacket it is and where it needs to be sent.

Layering Your Networkwith the OSI Model

Understanding all the elements of a modern telecommunica-tions network isnt necessarily an easy thing, so the folksat the ISO (International Standards Organization) helpfullycreated something known as the OSI Model, which providesan abstraction model for the network. The OSI model is alsoknown as the 7 layer model(because it has, unsurprisingly, 7layers!). Detailing the OSI model would take an entire chapter(at least), but Table 3-1 gives you a quick review of each of thelayers.



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Table 3-1 The OSI Model

Layer Function

1: Physical Layer Controls the actual electrical or optical sig-nals over the communications network

2: Data Link Layer Controls the physical addressing of signalsacross/between network nodes

3: Network Layer Controls the path of signals across the net-work, from host to host on the network

4: Transport Layer Controls the flow of signals from end-user toend-user across the network

5: Session Layer Controls the dialogues between individualcomputers/devices, such as the connection ofa PC to a web server

6: Presentation Layer Translates the syntax or format of databetween lower and higher layers

7: Application Layer Applications on a computer or smartphone

actually use this layer to access servicesacross a network

Each layer relies on the services of the layer below it and thatprovides services to the layer above it so if youre talkingabout a layer 7 service (like HTTP for websites), there aresix layers beneath that service that provide the networkingfunctionality required to make HTTP work. As you move up(numerically) in the model you move from the most basicmake a signal go across a wire functionality to the mostadvanced (deliver this service from that server to this indi-vidual device).

MPLS sits in a weird place when it comes to network proto-cols because its neither strictly a data link layer (Layer 2),like Ethernet or ATM or Frame Relay nor a network layer, likeIP, protocol (Layer 3). A service provider can instead, as itdesires, implement MPLS at either layer, on top of other pro-tocols. For example, MPLS can be deployed on an Ethernetnetwork (Layer 2) to provide IP services like Internet access(Layer 3). This ability is what provides the multiprotocol(MP)



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part of MPLS name. MPLS, when implemented across a net-work, simply doesnt care what the underlying Layer 2 proto-

col is, and allows traffic to be passed among different networksegments (from the core to the metro to the last mile/accessnetwork, whatever technology underlies them) while makingsure that packets get to the right place at the right time withthe right priority and level of service.

Discovering IP/MPLSA core or metro network that provides Internet Protocol (IP)services over MPLS is typically referred to as anIP/MPLSnet-work. IP/MPLS is one of the primary technologies used by allmajor carriers within their network cores the backboneof their intercity/region networks.

IP/MPLS is designed to provide the flexibility and service qual-ity of MPLS (see the preceding section) over an IP networkbackbone. The IP backbone network provides an inexpensiveand robust infrastructure for delivery of packets, but IP itselfdoesnt offer the kinds of service quality and assurance thata carrier needs to provide high-priority traffic (like real-timevoice and video).

Layering MPLS on top of an IP network allows the serviceprovider to use MPLS and its labels to specify which packetsget sent first to support traffic that requires more bandwidthor less latency. This prioritization ability makes it possiblefor the carrier to offer and charge more for services thatrequire guaranteed service level agreements, while offeringtraditional IP best efforts service for non-prioritized routingand queuing.

Understanding MPLS-TPMPLS-TP (the TP stands for transport profile) is designed toextend MPLS and its benefits beyond the core networks andinto the metro aggregation and access parts of the network byproviding a reliable packet-switching transport between thesenetworks. MPLS-TP does this by simplifying some elements ofMPLS in essence getting rid of the elements of MPLS thatarent necessary for a transport-oriented network.



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While MPLS-TP doesnt include all the elements found in theMPLS technical standards, its a kind of MPLS. You can think

of it as a subset of the full MPLS standard, with a few extraadditions to optimize it for transport network use.

The three main differences between MPLS-TP and the broaderMPLS standards are

The removal of MPLS elements that arent related toconnection-oriented data transport

MPLS-TP relies less on dynamic routing of data and moreon pre-defined and pre-provisioned routes.

Additional Operations and Maintenance (OAM) tools formonitoring the network

These tools operate in-band their signals can be trans-mitted within the MPLS-TP traffic without some sort ofexternal signaling network.

Support for a centralized Network Management System

(NMS) control

Centralized NMS is how carriers already manage theirSonet/SDH networks greatly reducing both the learningcurve and the overall operating expenses for the network.

While MPLS-TP can use a centralized NMS for manual configu-ration of traffic routes (calledLSPs or Label Switched Paths),it can also be configured to use a control plane for dynamicrouting, just like regular MPLS, if the carrier desires. Beyondthat, MPLS-TP differs from IP/MPLS in the following ways:

MPLS-TPs total cost of ownership (TCO) is lowerbecause it reduces the routing and control complexityof IP/MPLS by relying on static, pre-programmed routesrather than dynamic ones.

MPLS-TP focuses on transport functionality instead ofrouting, which eases the operation and maintenance, as

well as services provisioning.

Unlike IP-MPLS, MPLS-TP is a two-way(bidirectional)protocol. Traffic over an MPLS-TP network can be trans-mitted from point A to point B and back from point Bto point A over the same path. This aspect of MPLS-TPresembles traditional TDM transport networking easing the migration from existing network technologies.



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MPLS-TPs connection-oriented approach, along with itscircuit protection mechanism, is another natural evolu-

tion from carriers existing TDM transport networks.

MPLS-TPs deterministic and QoS-assured performanceenable wide deployment in the most dynamic parts of thenetwork.

MPLS-TP provides most of the benefits of MPLS as used incarriers core networks, while at the same time offering a sim-plified and pared-down approach thats both well suited tometro networks and familiar to carrier staff.



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Chapter 4

Moving to the OpticalTransport Network

In This ChapterMeeting the OTN

Learning the advantages of OTN

Realizing the role of OTN

Understanding the ODU cross-connect

Sonet and SDH have long been the primary standards fortransport networks over optical fiber networks (you can

find out more on Sonet and SDH in Chapter 1). Sonet/SDH isa mature, well-known, reliable, and resilient TDM-based net-work technology. Its been the bread-and-butter of transportnetworks for many years.

But Sonet/SDH has limits designed to max out at a speed of40 Gbps. While thats a lot of bandwidth, its increasingly notenough for overloaded carrier networks. Its a capacity thatsfalling behind the optics themselves, which are starting tosupport speeds of 100 Gbps and beyond.

So as you begin to plan your transport networks for an all-packet future, start looking at something new . . . and better.Thats where the Optical Transport Network (OTN) comes

in. OTN is a new standard or series of standards, defined bythe ITU, designed to provide a converged network infrastruc-ture capable of handling both legacy TDM traffic and todayspacket traffic with high reliability and speeds that far exceedthe limits of existing Sonet/SDH networks.



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You may also hear OTN referred to as G.709 (the main techni-cal recommendation or standard from the ITU which

defines OTN) or the digital wrapper(because it wraps multipleservices into a single OTN frame).

In this chapter, you discover what OTN is all about, the advan-tages of OTN over its predecessor Sonet/SDH, look into someof the components of OTN, including the ODU cross connect,and finally how OTN fits into the OMLT.

Looking into OTNWhats new about OTN (beyond the fact that its newer thanSonet/SDH) is that it finally began to gain momentum in carri-ers networks in 2011. So even though the standards have beenaround for more than a decade, OTN is now the next big thing.

An OTN is made up of a set of optical network elements con-nected by optical fiber links. Its able to provide functionalityof transport, multiplexing, routing, management, supervision,and survivability of optical channels carrying client signals.

OTN is a global standards-based mechanism for combiningdisparate services on an optical wavelength in the transportnetwork. OTN accepts different services as clients and thenmanages the transmission of these services over DWDM wave-lengths. Some of these services include

Ethernet

Sonet/SDH

IP or MPLS packets

ATM

OTN is the successor of Sonet/SDH, while at the same time fullysupporting Sonet/SDH traffic within its wrapper. OTN maxi-

mizes the efficiency of the network by combining more thanone lower bandwidth service to each of its higher bandwidthwavelengths. For example, a single 10 Gbps OTN wavelengthcould carry a mix of Sonet/SDH and Gigabit Ethernet traffic.



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Chapter 4: Moving to the Optical Transport Network 25

Table 4-1 shows the speeds of different variants of OTN.

Table 4-1 The Speeds of DifferentVariants of OTN

OTN Variant Maximum Bandwidth (Gbps)

OTU-1 2.7

OTU-2 10.7

OTU-3 43

OTU-4 112

Understanding WhyYou Need OTN

Carriers are working rapidly to replace or at least augmenttheir Sonet/SDH optical infrastructure with OTN. Why, youask? Because speedis the name of the game. You want toadopt OTN because its Ethernet services are moving from10GbE to 40GbE and even 100GbE. Simply put, OTN is theonly game in town when it comes to supporting this speed.Sonet/SDH simply doesnt go beyond 40 Gbps.

Speed, however, isnt the only driver for the adoption of OTN.

Other important drivers include the following:

OTN retains and even improves on Sonet/SDHs reliabil-ity even though it had been built from the ground up fordata services.

The advent of DWDM has made it much more attractiveto carry multiple wavelengths on each fiber for reasonsof capacity and efficiency.

Optical networks are growing larger and more complex,and scaling Sonet/SDH to support this complexity isbecoming increasingly difficult.

OTN supports Sonet/SDH, Ethernet, and many other ser-vice types (like fiber channel), allowing carriers to fullysupport legacy and next-generation services over theOTN infrastructure.



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OTN is transparent, meaning that it supports all the man-agement, operations and billing systems, tools, and auto-

mation used for existing services with no modification.

This fact makes it easy for carriers to train their person-nel to operate within an OTN environment.

OTN supports any service inside the payload, even if thatservice crosses multiple carriers networks.

OTN allows the mixing of synchronous services with dif-ferent clock sources, as well as asynchronous services,on a common wavelength.

OTN needs fewer wavelengths to carry a carriers traffic,simply because it can squeeze more services into eachOTN wavelength.

There is, alas, one big disadvantage to OTN: it requires newequipment. In most cases, implementing OTN is not an incre-mental upgrade (except where OTN-capable equipment hasbeen installed but not yet turned on); instead, it is what is

known in the industry as a forklift upgrade (which is to say,bring in a forklift and take the old equipment out for the junkheap). Given the compelling advantages of OTN and in par-ticular the pressing need for the speed of OTN, many carriersare coming to the realization that the time for OTN is now.

Examining the Functions of OTNOTN is designed as a replacement for Sonet/SDH, while stillproviding the ability to transparently carry existing Sonet/SDHtraffic from other parts of the network. OTN functionally mustdo many of the same things that Sonet/SDH does, such as hand-ing the processing of packets entering the network, controllingthe optical pathways used in the network, and so on.

Some of the key functions of the OTN include

Forward Error Correction: This mechanism increasesthe reliability of a telecommunications signal by addingredundancy to the signal. When the signal is receivedat the far end of the path, this redundancy allows anysignals that have been degraded to be correctly recon-structed, allowing OTN to use longer fiber pathways.



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Chapter 4: Moving to the Optical Transport Network 27

Mapping services: The OTN maps multiple services(Sonet/SDH, Ethernet, IP, and so on) into OTU (Optical

Transport Unit) frames to prepare them for transmissionacross the optical network. This mapping retains theoriginal services operations and management overheaddata, so performance and service assurance can be main-tained end-to-end.

Multiplexing: After services have been mapped into OTUframes, theyre multiplexed on DWDM wavelengths fortransmission across the optical fibers.

Management of optical paths and performance: OTNequipment determines the optimal paths for wave-lengths, sends them the right way, and monitors the per-formance of the optical infrastructure.

Understanding the ODU

Cross-ConnectThe Optical Data Unit Cross Connect (ODU-XC) is an essen-tial element of the OTN or any optical network for thatmatter. It provides the functionality to switch one opticalinput to another optical output. In simpler terms, a cross con-nect simply directs an optical signal from one fiber path toanother.

The ODU-XC is designed to do two things at once:

Provide connectivity between ports on the cross connect.

The ODU-XC can take an optical signal coming in on onefiber and send it out of the device (and across the net-work) on a different fiber.

Groom traffic by separating out portions of a multiplexedoptical signal and then re-multiplexing them and sending

them back out in a different multiplexed signal.An ODU-XC doesnt just take one big fat multiplexed opti-cal signal and send it somewhere else; instead, it canbreak that signal down and send its component parts todifferent locations.



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The ODU-XC is whats known as an opaque (or electronic)device. Opaque cross connects convert the optical signal to

an electrical signal (similar to the signals sent over a CAT-6copper Ethernet network or even over the DSL line runningto your home), route the signal in this electrical domain, andconvert it back to an optical signal on to the outgoing opticalpathway. This is known as an O-E-O conversion.



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Chapter 5

Understanding theRole of WDM

In This Chapter Understanding Wave Division Multiplexing (WDM)

Why do we need WDM?

Going coarse and going dense with WDM

Understanding multiplexers

Reconfiguring your WDM Network

Getting faster with 40 and 100G

Everywhere but at the edges of carrier networks (the lastmile that connects a customers home or business to

the network), fiber optic cables have replaced the old coppercables used in traditional telephone networks. In fact, many

businesses and some residences now have fiber running allthe way to the building meaning theyre on an all-opticnetwork.

Theres a very good reason that fiber has replaced copper.Well, there are a bunch of reasons, including that fiber costsless to produce, is physically smaller, is relatively immuneto interference from adjacent fibers (called crosstalk a bigissue for copper cabling), and can run farther distances than

copper. But the one very good reason why copper has beenreplaced by fiber is that fiber is faster. Alotfaster.



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But as fast as fiber is, growth in network data usage (drivenby a lot of things like Internet access, cloud computing, and

online video, to name just a few) constantly demands morespeed(or, in networking terms, more bandwidth). So just ascopper networks evolved from a single voice phone call on apair of wires to more complicated, multiplexed signals (like aDSL connection) running over that same pair of wires, fiber isevolving to put more data over a single fiber.

Part of this effort to send more data across fibers comes fromimprovements in how data signals are encoded on the fiber

and part of it comes from improving the optical elements thattransmit the light across the fiber. But perhaps the biggestbooster of this speed is the advent of Wavelength DivisionMultiplexing (WDM).

In this chapter, I talk about what WDM is, why its so great,and what types of WDM are out there. You discover the multi-plexers and equipment that support WDM and find out aboutthe new high speed channels that WDM enables.

Understanding What WDM IsIf youre familiar with the concept of frequency divisionmultiplexing (FDM) on electrical/copper networks (or inradio transmissions), you already may understand WDM.Essentially WDM uses different light wavelengths (frequenciesor colors) to transmit multiple signals over a single fiber atthe same time in one direction or bidirectionally. WDM canprovide an order of magnitude increase in the capacity of agiven fiber in the network.

You may hear wavelengths in a fiber optic system alsoreferred to in Latin, as lambdas or as channels (back to boringold English).

A good analogy for WDMs mechanism is to think about howradio works. A certain segment of the radio frequency spec-trum is dedicated to broadcast radio, and within that spectrumindividual stations are assigned their own frequencies. Whenyou listen to the radio, you dont tune in the entire AM or FM



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frequency range all at once; you tune into a specific frequency.WDM does the same thing with the range of light frequencies

available on a fiber, and by tuning in to the right wavelength,the devices on the far end of the fiber listen to only the datathey should, instead of all the data crossing the fiber at thesame time.

An optical fiber has limits regarding what wavelengths orfrequencies will travel through the fiber with minimal noiseand signal loss. But this limit is huge: An optical fiber caneffectively carry signals over a range of about 40,000 GHz of

frequencies. Thats 40 trillion Hertz a really wide rangeof frequencies. And a typical optical signal is only a few GHzof frequency wide. In other words, a signal only transmits in arange of a few GHz, while there are 40,000 GHz of frequenciesthat can be used in any single fiber. Given that equation, is itany wonder WDM came about?

Put on your thinking caps and remember your educationalphysics course. Light can be measured in one of two interre-

lated ways:

By its frequency (typically a range instead of a singlefrequency)

By the actual physical size of the wavelength

What about multimode? Is thatthe same as WDM?You may have heard of multimodefiber, which allows light to travel overseveral different paths through thefiber the light bounces aroundinside the fiber in different path-ways. Essentially, in multimode fiber,

the light is injected into the fiber atvarying angles allowing these differ-ent paths to be followed. This is dif-ferent than WDM, because a single

wavelength is used to propagate thesignal in multimode, rather than mul-tiple wavelengths as in WDM. WDMis primarily (though not exclusively)used in single-mode fiber, the kindfound in carrier networks (multimode

fiber is more typically used in LANsin a building or campus environmentwhere the fiber runs no more thanabout 1000 meters).



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The frequency is measured in Hertz (Hz), while the wave-length size is measured in nanometers (nm). Frequency and

wavelength are inversely proportionate, so longer wave-lengths correspond with lower frequencies.

Deciphering Whats SoGreat about WDM

WDM offers greater bandwidth over a carriers existing fiberinfrastructure. Thats a pretty great thing when you considerthe expense of buying new fiber, trenching, laying conduit,and actually installing more fiber. WDM lets a carrier get moreout of an existing investment and creates some future proofingfor the times when a carrier does need to lay new fiber.

Many carriers are adopting WDM for the following reasons:

Support for increasing bandwidth demand: The growthin new, bandwidth-intensive services (such as video,mobile, and cloud computing) shows no sign of abating,and carriers need to keep up with this demand.

Fiber utilization: Because WDM adds capacity to existingfiber without network additions, carriers can do morewith less.

Doesnt require a wholesale upgrade of the network:

Upgrading a fiber transport network to DWDM requiresnew devices on the network, but it doesnt require a com-plete replacement of the existing fiber infrastructure. SoDWDM can be an incremental upgrade, albeit one whichincreases network capacity by orders of magnitude.

Better performance for services: WDM provides abun-dant bandwidth and carries services (Sonet/SDH orEthernet) transparently, so carriers can deliver thoseservices with better performance and easily fulfill service

level agreements.

Faster provisioning: Adding additional capacity to a par-ticular network segment can be as easy as turning onan additional wavelength, instead of providing additionalfiber and other network resources.



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Future proofing: As DWDM systems improve, the gapbetween wavelengths on a fiber may be further reduced,

meaning that more wavelengths can be transmittedacross each fiber so future capacity increases may beable to be accomplished by replacing line cards insteadof trenching in new fiber.

Coarse versus Dense: CWDM

and DWDM TechnologyWDM technologies have evolved over the years as engineershave designed improved techniques and equipment. The ear-liest WDM systems left a lot of free space (a wider range)between wavelengths or colors in the system, to avoid anypossibility of interference and also in keeping with the lessprecise optical transmission and receiving equipment (theoptics) available at the time. Modern WDM systems leave less

space between the wavelengths and can therefore fit morewavelengths on a single fiber.

CWDMOne variant of WDM, lesser but still quite capable, is CoarseWavelength Division Multiplexing(CWDM). CWDM systemsuse broader spacing between wavelengths on the fiber. Thisapproach has a pro and a con:

The Pro: CWDM can use cheaper optical and other com-ponents because it requires less precision in the opti-cal domain. Cheaper components equal less expensiveequipment.

The Con: CWDM is less efficient than its successorDWDM (see the next section) because that wider spacingmeans fewer wavelengths can fit on a single fiber.

CWDM specs typically max out at 18 wavelengths on a singlefiber, but in practice, 8. CWDM systems are more frequentlyused in short range networks, while DWDM is used for longer.



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DWDMAnother variant of WDM isDenseWDM, or DWDM. DWDMuses less spacing between wavelengths to allow more of themon a single fiber as many as 128 per fiber, but in practice,88. DWDM provides greater bandwidth and spectral effi-ciency, but it costs more than CWDM (see the precedingsection) to install.

In addition to its greater capacity, DWDM offers the followingadvantages over CWDM:

Greater range (over 100 kilometers)

The ability to have the signal amplified instead ofregenerated

Regeneration requires an Optical-Electronic-Optical(O-E-O) conversion, which makes it more expensiveand can cause performance issues compared to amplifi-cation, which requires no conversion out of the opticaldomain.

A broader range of Operations, Administration andManagement (OAM) signals, simplifying the process ofoperating and managing the network

Multiplexing Your ServicesIn order to get all the wavelengths on a single strand of fiber,you need a multiplexer. The role of the multiplexer is prettysimple to understand, even if the engineering behind one isnot so simple: the multiplexer is the device that collects mul-tiple signals (or, in this case, services) into wavelengths to asingle shared fiber.

A WDM network has, in the simplest configuration, multiplex-ers at each end of a connection to collect signals, combinethem on a wavelength, and then, at the far end, separate themback into the original components. More complex networktopologies have multiple multiplexers, including multiplexers



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that can pass some wavelengths through to the next node onthe network while adding and dropping other wavelengths for

local delivery to customers or other networks.

Passive multiplexers and OADMsMultiplexers can use simple optics to perform their duties(meaning they dont even have to be plugged into electricalpower), or they may have processors that provide additionalintelligence to the problem. In this section, I discuss several

variants of multiplexers.

Defining passive multiplexersThe simplest multiplexers arepassive multiplexers. A pas-sive multiplexer uses optics and not electronics to combineand split wavelengths. If you think of how a prism can dividesunlight into a rainbow of colors, you have a good idea of themechanism involved in a passive multiplexer.

Because they dont do any O-E-O conversions and dont haveany active electrical components, passive multiplexers havesome serious advantages:

Theyre extremely reliable because they dont have anyelectronics to burn out or software to fail.

They dont require power, so theyre well suited forinstallation in outdoor cabinets and other places where

power is at a premium. Theyre simple to configure essentially a set-it-up-and-

walk-away proposition.

The downside to passive multiplexers is that when a carrierwants to make a change in configuration, a technician needsto manually change or add cards or other components todo so.

Looking at the OADM variantA variant of the WDM multiplexer is the Optical Add DropMultiplexer (OADM). In essence, an OADM is designed to add



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or drop optical wavelengths (individually or in groups) from afiber without converting the signal from optical to electric and

back again. So the OADM provides flexibility in the networkby allowing services to come on and off the network at placesother than the endpoints.

Theres not a hard and fast dividing line between multiplexersand OADMs. Many devices are modular and can accept differ-ent cards with either functionality.

Hitting the road with ROADMsTheReconfigurable Optical Add-Drop Multiplexer(ROADM,pronounced roh-dam) is an innovation that has made telcomengineers jobs mucheasier. A ROADM keeps optical signalsoptical while it moves them on and off individual fibers, and itdoes so in a way that can be remotely configured in softwareinstead of manually performed by a technician.

This benefit is huge for carriers because they dont have tospend a lot of time planning for future network requirements,and they dont need to send a team of technicians to performa network modification.

Moving to 40G and 100GMost optical networks, even WDM networks, max out at 10

Gbps of bandwidth on each wavelength a speed that cor-responds well with the fastest common variant of Ethernet (10Gigabit Ethernet). However, with all things related to band-width, a lot is never enough.

An evolution is occurring toward even faster channels specifically to 40 Gbps and 100 Gbps speeds. (These speedscorrespond to new, faster variants of Ethernet.) In fact, themove is increasingly to skip over 40 Gbps and move directly

to 100 Gbps thats how much the bandwidth requirementsin transport and core networks are growing.



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Some vendors are offering solutions that essentially inversemultiplex, or combine several 10 Gbps wavelengths to create

a faster 40 Gbps virtual connection. Thepreferred methodisworking on solutions that bring 40 or 100 Gbps over a singlewavelength because this solution has better performance,power consumption, efficiency, and network management andcompatibility.

In order to reach these speeds, vendors have to create muchmore advanced optics (the receivers, transmitters, andrelated equipment that actually create the light that travels

across the fiber) as well as advanced signal processing tocompensate for errors and signal losses.

An important factor to consider when reviewing a 40 or 100Gbps option is the impact of these wavelengths on otherwavelengths going across the fiber. Not all 100 Gbps solutionswont cause transmission issues with 10 or 40 Gbps wave-lengths on the same fiber.



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Chapter 6

Ten Reasons for Evolvingto OMLT

In This Chapter Converging network trends and increasing bandwidth

Reducing network costs

Enjoying an access-to-core solution

Grooming at the right layer

Managing your network with carrier-grade OAM

In this chapter, in trueFor Dummies fashion, I give you agem of a reference when you want to quickly remind your-

self of why you need to evolve to OMLT for your business.This chapter lists the top ten reasons.

Increased Bandwidth Demandfrom All Applications

Bandwidth demand is going through the roof. Its an old story,one thats been repeated for decades as new applicationsand services move beyond early adopters and become main-stream. The cycles of bandwidth demand have overlapped,

without a break, for years and theres no sign of leveling off.This isnt a case of boom and bust, but rather a sustainedboom which can be measured in decades.

Mobile services, video, and cloud services drive this needfor customer bandwidth. Because of these services and thedemand for more bandwidth, switching to OMLT is a good idea.



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Increased Pressure toReduce Network Costs

Competition in the telecom market is fierce and, when com-bined with technological advances, has lead to an increasedcommoditization of bandwidth and downward pressure onpricing. Customers are paying a lot less today for a lot morebandwidth. In order to remain viable and profitable, carriersmust lower the cost of building and operating their networks.

And they can do just that with the OMLT because it

Contains a highly-integrated approach to convergedpacked and optical networking

Provides a mechanism for a carrier to improve thenetwork

Offers more/better/faster services without adding multi-ple expensive and complimentary devices to the network

Is built around a modular, pay-as-you-go approach, soa carrier need only buy whats needed today and thenspend money on incremental upgrades when neededinstead of paying upfront for more network than isneeded

Reduced TCOMany factors go into the total cost of ownership (TCO) of anetwork. By highly integrating functionality in a single device,the OMLT provides carriers a way to install and configureless equipment while still getting the same functionality as abest-in-breed approach with separate DWDM, OTN, and CESRequipment.

Not only does this integration mean less devices to install,

maintain, configure, and operate, but the OMLT also relieson a single, unified, and familiar management system alot fewer consoles and UIs for network techs to learn andmanage.



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Reduced Power ConsumptionReducing power consumption may, at first glance, sound likea vague, wishy-washy concern for a telecom network opera-tor. But reducing power consumption isnt just a green con-cern, its vitally important to carriers for a few reasons:

Power costs money and adds to the monthly operatingexpenses.

The infrastructure to provide power is expensive and

takes up real estate in COs, collocation facilities, datacenters, and outdoor pedestals.

More power consumed means more heat to deal with incarrier facilities, and HVAC (heating, ventilation, and airconditioning) systems dont run for free.

The more power required to operate a particular nodeof a network, the more backup generation capacityrequired.

Simplified ManagementBest-of-breed approaches, with separate equipment (oftenfrom different manufacturers) for each element of the overalloptical/packet converged network require this expensivelabor to learn and use multiple management systems just to

get the job done, day after day. The OMLT benefits from

An integrated, end-to-end management that uses a singleinterface for controlling both the network itself and alsothe services that are carried across it

Sonet/SDH-like management exceedingly familiarto most telecom engineers and techs applied to thepacket services world, simplifying day-to-day operations.

With the OMLT, carriers can spend less time managing theirnetwork and more time innovating with new services.



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Supported ServicesHow many times has your network streaming movie stoppedto rebuffer while youre watching it? Blame that on the band-width issue that cant support the large files of movies.

One way to avoid the dueling pitfalls of network demand fore-casting is to build a flexible network. Flexibility means morethan just being able to add bandwidth when needed but alsobeing able to support whatever kind of service a customer

requires, whenever required.

OMLT can provide anykind of service just by selecting andinstalling the right line cards. So a chassis thats set up on dayone to provide just wavelength services can begin providingcarrier Ethernet services with a simple upgrade. Or legacyprivate line Sonet/SDH services can be supported and thenupgraded to OTN, again just by adding or changing a line card.

Improved Time to Marketfor New Services

As carriers work to understand the future needs of their cus-tomers and to remain competitive, they need to be able to rollout new services as quickly as possible with minimal capitaloutlays and without incurring tons of new operating costs.At the same time, they need to provide levels of service thatkeep the customers coming back for more.

OMLT is just the ticket for todays carrier environmentbecause theres no need to configure multiple systems in thenetwork to launch and provision the new service OMLTdoes it all in one system.

Access to Core SolutionCarriers have traditionally spent too much time and moneybuilding out different networks for the various segments oftheir overall network one technology and set of vendorsin the access network, another in the metro network, and yet



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another in the core. This adds cost and complexity not only interms of buying and installing the equipment but also in terms

of business processes and supplier relationships.

The OMLT was designed from the ground up to be an end-to-end solution with equipment designed for everything from theaccess network right through to the metro and core. All use aunified management system from a single vendor.

Groom Services at the RightLayer, in the Right PlaceThe OMLT allows carriers to get the most network utilizationfor the least amount of money by providing mechanisms forgrooming traffic and services at the right layer at the rightpoint in the network. In other words, it is expensive (in termsof equipment capex and opex) to rely on the router (which

operates at Layer 3) to do all of the heavy lifting of directingyour services traffic through the network. Its best to reservethe comparatively scarce resource of routers for only thattraffic that needs it.

Instead, its cheaper and easier on the network to groomservices at lower layers whenever possible. OMLT providescarriers the ability to switch services at the wavelength layer.Carriers can choose which of these capabilities to implement

and where to implement them in the network based on ser-vice requirements.

Improve Network ReliabilityCarrier networks absolutely require high reliability and avail-ability. Its written right into customer contracts, and you betthat network providers compete on reliability and service

assurance, and they directly lose money and business whenthey cant maintain it.

A big part of ensuring the network is reliable is the ability ofthe OAM (Operations, Administration, & Maintenance) systemto monitor performance, track faults, and discover the rootcauses of network issues. Its much easier for carriers to



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monitor and maintain an OMLT network than it would be witha traditional, mixed-vendor/mixed-technology network. And

when an outage occurs, this unified OAM makes it easier fornetwork operators to identify the issue and fix it minimiz-ing the outage time.



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