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IPTV AND BROADBAND INFRASTRUCTURE

USING OPTICAL+ETHERNET NETWORKS

The strong worldwide demand for next-generation broadbandservices is driving service providers to invest heavily in first-mile access technologies such as DSL, HFC and FTTH. Now,end-user bandwidth is set to rise dramatically as new IPTVvideo service bundles are offered. To remain competitive andprofitable, providers need cost-efficient, scalable second-milesolutions that provide affordable backhaul to their servicenodes.

The deployment of high-capacity Internet Protocol TV (IPTV),video, data and triple play services presents service providerswith many challenges. The tremendous increase in servicebandwidth combined with unpredictable service adoption,leads to uncertainty in traffic patterns and required capacity.So backhaul networks that provide very high scalability andflexibility for future traffic demands must be planned anddeployed. The over-riding imperative is to do so at the lowestcost, both initial and ongoing.

Optical+Ethernet transport solutions provide the answer,thanks to the enormous bandwidth scalability of opticaltransport and the widespread adoption of Ethernet as the

low-cost transport protocol for these new services. This whitepaper examines how scalable, low-cost Ethernet over CoarseWavelength Division Multiplexing (CWDM) provides carrierswith a reliable and economic method to support new servicesand future capacity growth. Optical networking plus Ethernetprovides the ideal Fibre-to-the-Node (FTTN) infrastructure fornew IP-DSL Access Multiplexers (DSLAMs) and also todaysATM-based DSLAMs and legacy SONET/SDH services.

Table of contents:

Next-generation services: from one-play to bundles 2Flexible Optical+Ethernet network infrastructure 3Evolution of broadband technology to Ethernet/IP 4Requirements in the second-mile: access backhaul 5Architectural choices and goals 6Optical backhaul for cost-optimized multi-services 7Future evolution: the right technology 9Author: Stephan Rettenberger, ADVA Optical Networking

June 2007

The Fiber Service Platform (FSP) is a

family of innovative products that

provide comprehensive Optical+Ethernet

networking solutions for access, metro

core and regional networks. ADVA

Optical Networking is focused on the

needs of enterprise and service provider

customers deploying data, storage, voice

and video applications.

ADVA Optical Networking Inc.

2007. All rights reserved.

LEGAL DISCLAIMER: The informationprovided in this document is distributed

as is without any warranty, eitherexpress or limited.


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Next-generation services: from one-play to bundles

High-speed Internet access, peer-to-peer video gaming and multimedia download havedriven residential customer demand for high-speed connectivity. The Windsor Oaks Groupestimates more than 271 million fixed broadband subscribers worldwide at the end of 2006,with a CAGR of 12% to 533 million at the end of 2012. Yet customers demand more. Videoservices (increasingly offered using IPTV) are recognized as the key to higher ARPU andbundled services that include data, voice and video triple play are being launched.

DSL accounts for the majority of broadband connections in Europe and more than 64% ofthe worldwide broadband market. It retains its stranglehold versus Hybrid Fiber Coax (HFC)and other high-speed offerings such as Fiber-to-the-Home (FTTH). DSL is the key first-miletechnology for both residential users and the fast-growing small-office/home-office (SOHO)market.

The future of the market will be driven by personalized multimedia; for example, videoofferings such as childrens TV, TV replay, music videos and 2-way video calling haveproven successful for FastWeb in Italy. What seems to be needed is a one-play focusedvideo service. Whether one-play or triple play, different operators invest in different growthstrategies, but they all recognize an exploding bandwidth demand perhaps even an orderof magnitude increase in the next 5 years which must be met by the network.

The different services in the triple play package have different characteristics andrequirements regarding bandwidth and network performance1:

:: IPTV (broadcast) uni-directional service, normally multi-casted, 4-6Mbit/s

peak bandwidth per channel and medium requirements on jitter and delayperformance perhaps rising to 10-20Mbit/s for HD video services;

:: Video-on-Demand (VoD) uni-directional unicast service, 4-6Mbit/s peakbandwidth per movie and medium requirements on jitter and delayperformance;

:: Voice-over-IP (VoIP) bi-directional service, 40kbit/s per voice channel andstringent requirements on jitter and delay performance;

:: Internet access asymmetric service, uplink 5kbit/s and downlink 50kbit/saverage per user during peak hours and loose requirements on jitter and delayperformance.

The challenge? Service provider revenue is growing only slightly in value, yet the volume oftraffic and users continues to increase, both in industrialized and developing countries.Infonetics Research estimates IPTV subscribers grew by 166% during 2006 to reach7.2million worldwide and this is just the beginning of the next phase in broadband growth.In the big picture, control of cost is thus essential, and it is obvious that networkinfrastructure has a decisive role in cost-effectively accommodating such rising bandwidthdemand.

1 Values are based on a generic model. Actual numbers may vary.


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Flexible Optical+Ethernet network infrastructure

DSL access is capable of supporting todays varied service requirements. Yet next-generation broadband services require higher capacity, driving an increased penetration ofFiber to the Node (FTTN) with Very-high-rate DSL (VDSL)/VDSL2 drops to the end-customer. Cable TV systems, using coax feeds to the end-customer, are more than capableof supporting the varied service requirements, yet they too require an increasing capacity.

Even as extreme competition drives prices downwards, service providers need to offerhigher Quality of Service (QoS) to ensure viewers maintain their Quality of Experience(QoE). They need to offer high availability services and still higher capacity to the end-user.

Looking ahead, FTTH ONT and OLT growth is forecasted at 50% (Dittberner Associates) andis widely expected to be the engine of broadband growth in many countries. And with the

transition to HDTV video services, its clear that capacity demand will not reduce in theforeseeable future.

BSR

Broadcastserver

Video on Demandserver

IPbackbone

Set-topBox (STP)

1n

Internet

TV/Video

Ethernet transport

Voice

Figure 1: Triple play next-generation access scenario

New second-mile network technologies such as Carrier Ethernet and CWDM transport haveproven less costly than legacy SONET/SDH and ATM architectures and enable carriers tocost-effectively manage the large amounts of bandwidth required. By usingOptical+Ethernet transport to process multi-Gigabit/s of Ethernet traffic onto protectedoptical fiber, service providers enjoy uncompromised availability and scalability coupledwith dramatic improvements to operational efficiency and future flexibility (Figure 1).

As a result, CWDM optical technology is accepted as an essential part of next-generationbroadband, whether it is based on DSL or based on alternative technology such as HFC. Theintegration of Ethernet packet technology brings advantages in terms of network utilisationand link efficiency, as packet data traffic grows to rapidly eclipse TDM traffic types.


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Evolution of broadband technology to Ethernet/IP

The Windsor Oaks Group reports that (Figure 2): DSL will remain the dominant broadbandtechnology, with 64% of total fixed broadband subscribers. FTTH will offer the strongestgrowth opportunity with 29% CAGR, while cable will be the lowest at 9%.2.

600.000

500.000

400.000

300.000

200.000

100.000

0

2004 2005 2006 2007 2008 2009 2010 2011 2012

Source: broadbandtrends.com

Global Broadband Subscribers by Type, 2004-2012

DSL Cable Modem FTTH Other

Subscrib

ers

(000)

600.000

500.000

400.000

300.000

200.000

100.000

0

2004 2005 2006 2007 2008 2009 2010 2011 2012

Source: broadbandtrends.com

Global Broadband Subscribers by Type, 2004-2012

DSL Cable Modem FTTH Other

Subscrib

ers

(000)

Figure 2: Global broadband subscribers, forecast by technology

Following the commercial introduction of DSL, the technology has undergone substantialinnovations to increase supportable bandwidth/distance. Today, Asymmetric DSL2 (ADSL2)and ADSL2+ are available. These International Telecommunication Union (ITU-T) standardsdeliver 12Mbit/s and more than 25Mbit/s maximum capacity downstream, respectively.Further increase in capacity is provided by VDSL2 (ITU-T G.993.2) to provide 100Mbit/ssymmetrical up and downstream over short loop lengths.

Older generation DSLAMs use ATM as the underlying aggregation mechanism for connectingto the carrier network. Backhaul to the metro core is based on SONET/SDH, typically atOC3/STM-1, 155Mbit/s. However, as bandwidth needs increase and the service mixchanges, this first-generation architecture is no longer adequate and is being supplanted.

The latest DSLAM technology uses Ethernet and IP with Gigabit Ethernet (GbE) uplinks.Related DSL network technology, such as the Broadband Services Router (BSR), which

typically sits at the metro core and manages traffic flow, follows this trend. As illustrated inFigure 1, Ethernet is emerging as the next-generation IPTV transport mechanism all theway to the customer premise, where the set-top box signals channel changing. InternetGroup Management Protocol (IGMP) supports multicast applications.

In such a network architecture, the fine granularity of SONET/SDH transport becomes anexpensive liability. In this case it is far more cost-effective to use CWDM and manage high-capacity GbE connectivity and processing at the wavelength level instead.

2 Courtesy The Windsor Oaks Group, May 2007


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Requirements in the second-mile: access backhaul

Successful rollout programs for next-generation bundled services require more thanpowerful first-mile access technologies, however. The second-mile of the access networkcan easily become the bottleneck, thus carriers also need a scalable FTTN transportsolution. Protected, low-cost backhaul of aggregated DSLAM traffic to the metro/core is keyfor long-term service success and profitability. CWDM provides an excellent solution, incombination with Ethernet.

Further, the transition to FTTN/VDSL2 and FTTH architectures using various types of PON orother technologies requires careful planning, to ensure that future flexibility is notcompromised. Any second-mile solution must offer high scalability for the future but alsodeliver low first-in costs today. What are some of the key requirements to consider?

CAPACITY AND TOPOLOGY

We take a simple example of a DSLAM supporting up to 500 subscribers in a geographicalserving area. A triple play service model in todays market, such as that describedpreviously, might create the following bandwidth requirements per DSLAM:

:: 400Mbit/s for 80 active TV broadcast channels at 5Mbit/s each;

:: 125Mbit/s for 500 VoD subscribers (5% activity rate) at 5Mbit/s each;

:: 25Mbit/s for 500 Internet subscribers, at an average of 50kbit/s, and

:: 4Mbit/s for 500 voice subscribers (20% activity rate) at 40kbit/s.

The total aggregated bandwidth per DSLAM, then, is 554Mbit/s (400+125+25+4) so thatproviding 1Gbit/s per DSLAM for backhaul to the metro core is sufficient in this simple case.Note however, that using VDSL to enable multiple video stream delivery could increasebandwidth demand still further, as could a higher service activity rate, or indeed, use ofhigh-capacity uplinks for peer-to-peer applications. A jump to HD video might drivecapacity to 2Gbit/s, depending on the usable compression. Scalability is key and a backhaulcapacity rising to several Gbit/s might eventually be required.

For most service providers, fiber cost plays a significant role. Availability of dark fiber maybe limited or even non-existent, requiring costly lease arrangements with another carrier. Itis, therefore, critical to choose a topology and technology that supports efficient use of fiberinfrastructure no matter whether it is owned or leased.

Ring topologies have proven to be the best choice for any type of network scenario in whichtraffic must be backhauled from multiple locations to a central point. Initial investment andongoing operational costs are relatively attractive. The physical ring requires only one fiberpair, allows efficient protection mechanisms and is easy to operate.

Logical traffic patterns between DSLAMs and the BSR are hub and spoke and match thismodel perfectly. Typically, three to five DSLAM access nodes are connected to one hubnode and can be easily supported using CWDM access rings with growth headroom.


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Architectural choices and goals

Recalling the big picture imperatives discussed earlier, in order to drive cost out of an IPTVnetwork infrastructure, operators need to pay attention to several priorities (Figure 3):

:: Eliminate network layers by integrating optical and Ethernet technology;

:: Increase network efficiency by circuit multiplexing and packet aggregation;

:: Deploy operationally simple technology;

:: Automate using provisioning, management and OAM facilities;

:: Flexible node processing: pass-thru, add/drop, drop & continue

ISPEthernet layer Intelligence Virtual connectivity Packet efficiency

Metro hub node

Optical layer Scalability Protection Fibre efficiency

Optical+Ethernettransport node

PON-ONT IP-DSLAM

BSR

Videoserver ISPEthernet layer

Intelligence Virtual connectivity Packet efficiency

Metro hub node

Optical layer Scalability Protection Fibre efficiency

Optical+Ethernettransport node

PON-ONT IP-DSLAM

BSR

Videoserver

Figure 3: Metro access generic network layer architecture

Considering that there is often a shortage of fibre in metro and access areas, that GbE andlegacy services must be supported from OC3/STM-1 to 10Gbit/s and that reliable androbust protection schemes are needed, optical networking is a clear-cut solution. With a

judicious integration of Ethernet, traffic efficiency can be greatly increased whilst low costsare maintained since the complexity of a full L2 Ethernet network is avoided. Thus, thisapproach tends to provide the lowest cost per bit in a wavelength the bottom line.

OPERATIONAL EXPENSE

It may seem trite to state that network characteristics have a high impact on operationalexpense, but that is precisely the case. Opex is notoriously difficult to quantify, but severalOptical+Ethernet attributes provide confidence that opex can be controlled. For example,transport-centric networks are intrinsically simpler than switch-centric networks. CarrierEthernet is still developing as a mainstream approach and an optical layer OAM providesproactive alarms, clean fault diagnosis and fast troubleshooting. Service management issimpler (point-to-point vs multipoint) and since there are fewer and less complexparameters, configuration is simpler as well. Finally, the well-known rapid and reliableprotection mechanisms of an optical layer ensure high availability and support low costs.


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Optical backhaul for cost-optimized multi-services

Optical networks have a long history of success. High capacity Dense WDM (DWDM)systems are the foundation of todays backbone networks. Scalable multi-service ringsconnect central offices around metropolitan areas and expand into regional networks, whilededicated implementations support mission-critical applications for large corporations. Thevalue proposition of WDM is clear: lowest-cost-per-bit transport, support of any protocoland bit-rate, high scalability and future-proofed for network growth.

Carrier-class CWDM systems expand the application of the technology still further. Utilizingwider wavelength spacing than DWDM, CWDM uses low-cost components to deliver up to10Gbit/s per wavelength. Such systems are extremely attractive in price; they are a perfectfit for FTTN backhaul requirements in an access network, where cost sensitivity is veryhigh.

Logicalconnection

WiMAX

ADSL /ADSL2+

FTTC(VDSL, HFC)

FTTHPON

FramerGbE-ADM

L2 card

1 ..... 20

VDSL

GbE-ADM

Lowest-cost transport for GbE pipes:

Pass-thru

Add/Drop

Drop&Continue (broadcast)

Integrated L2 functionality

Lowest-cost transport for very high GbE count,only partially filled (statistical gain):

L2 based aggregation into 10G

Multicast support

Logicalconnection

WiMAX

ADSL /ADSL2+

FTTC(VDSL, HFC)

FTTHPON

FramerGbE-ADM

L2 card

1 ..... 20

VDSL

GbE-ADM

Lowest-cost transport for GbE pipes:

Pass-thru

Add/Drop

Drop&Continue (broadcast)

Integrated L2 functionality

Lowest-cost transport for very high GbE count,only partially filled (statistical gain):

L2 based aggregation into 10G

Multicast support

Figure 4: Broadband backhaul via CWDM rings

CWDM rings with a Gigabit-Ethernet-Add-Drop Multiplexer (GbE-ADM) function provide veryadaptable, flexible configurations. For example, multiple DSLAMs can be connected to theservice node at a metro core hub using a single wavelength (illustrated in Figure 4). Ordifferent networks, for example the PON network, can be deployed on a separatewavelength. This has obvious advantages for future scaling and network isolation. Use ofseparate wavelengths also opens the door to access unbundling and wholesale serviceofferings.

WDM also allows easy integration of DSLAM-based broadband networks using SONET/SDHor ATM interfaces. In some cases, the mobile network can be converged onto the sameaccess infrastructure in order to take advantage of common backhaul.


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GBE-ADM: COST-EFFECTIVE ETHERNET TRANSPORT

The GbE-ADM function is a new capability introduced by ADVA Optical Networking, whichprovides flexible pass-thru, add/drop and drop&continue functionality of four GbE channelsat a particular node. The GbE channels are multiplexed onto a 4Gbit/s wavelength channelfor transmission around the ring.

Different approaches exist when it comes to protecting services against various networkand equipment failures. Cost sensitivity is high in access networks, and protection againstfiber cuts is the main concern. The best strategy is to perform protection at the lowestnetwork layer possible, in this case the optical layer.

The ring architecture here allows an easy 1+1 full optical line protection capability, bysending the 4Gbit/s aggregate wavelength channels both ways around the ring, clockwise

and anti-clockwise. Switchover in the rare event of failure should be extremely fast, lessthan 50ms, and is performed by the receiving transponders at the head-end.

This architecture also supports a nodal drop & continue functionality. This has proveninvaluable in easily provisioning and delivering TV broadcast services, at maximum networkefficiency. Nodes simply access the required GbE stream while the stream is in transit atthe node. Other operating configurations include pass-through and add/drop mux.

CWDM rings with GbE-ADM function offer a compelling set of advantages:

:: highest data transport capacity for lowest operational cost;

:: wire-speed Gigabit Ethernet with node pass-thru, add/drop or drop&continue;

:: low latency, high QoS and no packet loss;

:: easy network overlays for different services or different operators;

:: simple and transparent managed FTTN infrastructure;

:: SONET/SDH-like simplicity, with no need for optical link engineering, opticalamplifiers or power balancing (less operational complexity);

:: fast and automatic optical-layer protection mechanisms with client OAM;

:: easy combination of legacy services such as ATM on a single fiber, and

:: efficient backhaul of multiple DSLAMs per node through the use of TimeDivision Multiplexing (TDM) to a 4Gbit/s wavelength.

In summary, the use of technology such as GbE-ADM increases the efficiency of thesystem. MPEG video compression technology squeezes video into a lower bandwidth whileGbE-ADM and CWDM squeezes those channels onto a transport network at lower cost.


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THE IMPLICATIONS OF VDSL

The commercial availability of VDSL2 technology enables service providers today to deliverup to 100Mbit/s over a pair of twisted copper cable. IPTV offerings in High Definition TV(HDTV) quality combined with a strong Video on Demand (VoD) component clearly benefitfrom this technology. On the downside, however, the distance capability of VDSL is reducedversus ADSL, and the DSLAM needs to move closer to the end-user in many cases withinthe range of less than one kilometer. The resulting Fiber-To-The-Curb (FTTC) architectureimplies that typically the number of subscribers per DSLAM is significantly lower than in theADSL case. The number of GbE ports back at the mini Pop, on the other hand, increases,since there are in average more VDSL-based DSLAMs at the curb than ADSL-based DSLAMsat the node. Figure 4 shows the architectural difference.

The higher number of GbE ports in the VDSL scenario drives also a higher amount of total

bandwidth in the second mile although the individual GbE ports may only be partially filled.In that case network efficiency and costs of the backhaul architecture can be furtherimproved by using a 10Gbit/s aggregate channel with increased Ethernet processing. Thisarchitecture scales well to meet future demand, without costs spiraling out of control.

Future evolution: the right technology

Carriers around the globe are preparing to launch high-capacity next-generation broadbandand video services to their residential and SOHO customers

DSL plays a key role in enabling IPTV, video and triple play services to end-users over first-mile copper networks. In the second-mile of the access network, optical transport solutionsare ideally suited to provide cost-efficient backhaul of growing traffic volumes to the metrocore. CWDM rings, in particular, have the right cost points and functionality to secure fastreturn on investment and ensure long-term scalability and efficiency for FTTN/VDSL2architectures.

The optimal use of Optical+Ethernet transport technology can ensure maximum bandwidthefficiency for both circuit and packet distribution and backhaul in high capacity applications.The integration of L1 and L2 network layers provides simpler operations and lowest cost-per-bit transport. GbE-optimized muxponder and ADM cards deliver the lowest latency and

jitter and zero packet loss. As packet traffic comes to dominate, further efficiencies are

possible by integrating additional L2 packet processing into the optical layer.

The promise of video services and IPTV technology is driving huge changes in the first- andsecond-mile backhaul networks. A flexible approach is required to support diverse servicessuch as xDSL and PON with unpredictable demand without making expensive up-frontcommitments. Optical+Ethernet networks allow service providers a freedom with low first-in cost and massive scalability plus increasing efficiency via TDM and packetgrooming/multiplexing.

ADVA Optical Networking delivers the integrated Optical+Ethernet difference: Operationalsimplicity, more revenue and lower cost.


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