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2© 1999, Cisco Systems, Inc. 2031085_06F9_c1
Introduction to xDSLIntroduction to xDSLTechnologyTechnology
Session 203Session 203
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Introduction to DSL TechnologyDigital Subscriber Line (DSL) technology unlocks the potential ofconventional copper pair telephone wire to deliver high-data-rate("broadband") digital services. Learn how this technology "turbocharges" the telephone wires available at virtually every businessand residence, and how this technology will effect you as aservice provider, enterprise customer, and everyday consumer.DSL is one of the leading technologies for bringing "megabits tothe masses" in the new emerging age of ubiquitous broadbandaccess. This session includes introduction to the family of DSLtechnologies ("xDSL"); describes how this technology enablesdelivery of high-speed data, voice and multimedia overconventional telephone wires; overview of the equipment requiredto build a DSL network on top of existing telephony infrastructure;description of value-added services enabled by "mass-market"broadband access.
AbstractAbstract
“
”
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AgendaAgenda
• What Is “Broadband”?• Why Is It Important?• What Is DSL?• DSL Technology Overview• Basic DSL Network Design• New World Services• Market Dynamics
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56K Is Too Slow to Provide a SatisfactoryConsumer Internet Experience
Life Beyond 56KLife Beyond 56K
• Our century-old telephone network is designed specificallyaround the audible frequency range 0-4 kHz
• Voice-band modems use tones in the audible spectrumand communicate via standard voice circuits (You canhear modems and fax machines “talking” to one another)
• 56 kbps (“56K”) is the practical limit for voice-band modems
• DSL uses inaudible high-frequency signaling to achievemegabit-transmission speeds
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10x 20x 30x 40x 50x 60x 70x 80x 90x 100x
“Broadband” = “Megabit” Data Rates
56K
4Mb70x
2Mb36x
T-127x
1Mb18x
384K7x
What is “Broadband”?What is “Broadband”?
• Common unit of measure: “T-1” = 1.544 Mbps• “Fractional” T-1s, starting around 384 kbps• Compare to current maximum voice-band
modem speed of 56 kbps (“56K”)…
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Broadband Access TechnologiesBroadband Access Technologies
• DSL (copper)
• Cable (coax)
• Wireless
• Optical Fiber
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Consumer Access OptionsConsumer Access Options
Analog
ISDN
ADSL
CableModem
Satellite
LMDS(FixedWireless)
Requirementsand Limitations
Slow, ButAvailable
Everywhere
Reach ExtendsSeveral Miles
with Repeaters
<18K ft. fromCO, No DLC
Requires CableTV Availability;Speed Varies
Noticeably withSubscriber Load
Requires “Dish”Antenna andPhone Line
RequiresAntenna
InstallationCost
$0 (WithExisting
Phone Line)
Up to$300
Up to$500
Up to$175
Up to$800
Negotiated,Dependson Serv.Package
MonthlyExpense
Cost of PhoneLine + $19
for ISP
$19-$39 +$19-$39for ISP
$39 (Min), MayInclude Internet
Connection
$29-$49 (Min),Include Internet
Connection;May Include
Equip. Rental
Cost of PhoneLine + $29-$129,Include Internet
Connection
Varies Widely,Dependson Serv.Package
TransmissionMedium
Coax
Wireless
Copper(Std. Phone
Wire)
Copper(Std. Phone
Wire)
Copper(Std. Phone
Wire)
WirelessReq.'s
(Phone LineReturn Path)
DownloadSpeed
56 Kbps(Typically
less)
64 Kbpsor
128 Kbps
400 Kbps
384 Kbpsto
4 Mbps
144 Kbpsto
8 Mbps
1.5 Mbpsto
4 Mbps
UploadSpeed
33.6 Kbps(Or Less)
33.6 Kbps(Via 56KAnalogModem)
64 Kbpsor
128 Kbps
144 Kbpsto
1.7 Mbps
128 Kbpsto
4 Mbps
1.5 Mbpsto
4 Mbps
TargetMarket
Residential
Residentialand
Business
Residential
Residential
Business
Residentialand
Business
EquipmentCost
$0 (TypicallyIncludedwith PC)
$75 TerminalAdapter to
$500 Router
$200 PC NIC,$500 SOHO
Router(Unless Rented)
Up to $349 forSet-Top Modem,Unless Rented,Plus $29 (Min)
for Ethernet NIC
$199 (Min.)
Negotiated,Dependson Serv.Package
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Deregulation and Access to “Dry Copper” HasCreated a Market for CLECs and IXCs to Provide
Lower-cost DSL Access As an Alternative toReselling Traditional Local Loops
ServiceServiceLeased Line T-1 (1.5 Mbps)Leased Line T-1 (1.5 Mbps)
Frame Relay (384 kbps)Frame Relay (384 kbps)
Business ISDN (128 kbps)Business ISDN (128 kbps)
DSL (1.5 Mbps)DSL (1.5 Mbps)
DSL (384 kbps) DSL (384 kbps)
InstallationInstallation$750-$1,500$750-$1,500
$700-$1,200$700-$1,200
$100-$350$100-$350
$400-$1,000$400-$1,000
$100-$350$100-$350
MonthlyMonthly$1,200-$1,600$1,200-$1,600
$550-$850$550-$850
$100-$250$100-$250
$900$900
$100-$150$100-$150
Business Access OptionsBusiness Access Options
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RBB Enables the Full CommercialPotential of the Internet
Why is ResidentialWhy is ResidentialBroadband Important?Broadband Important?
• Fast downloads of“rich” content
Graphics, animation, audio,and video
• Always onConstant interaction with amultitude of network-aware“Internet appliances”
• Real-time, person-to-person interaction
Video conferencing, interactivegaming, multimedia collaboration
• Integrated servicesData,Voice, and Video
• New ServicesVariable bandwidth, additionallines on-demand, multimediaconferencing
• Relieves voicenetworks overloadedwith Internet traffic
Average voice call lasts threeminutes, compared to 30-60minutes per internet session
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POTS
POTS
SDSLSDSL
ADSLADSL
1 MHz4 kHz0
What Is “DSL”?What Is “DSL”?
• A family of access technologies thatutilize high-transmission frequencies(up to 1 MHz) to convert ordinary phonelines into high-speed data conduits
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DSL“Modem”
Value-AddedPacket
Network
End-User
DSL“Modem”
DSL
Copper LoopEnet ATM
DSL 101DSL 101
• DSL is a pair of “modems” on either end of a copper wire pair
• DSL converts ordinary phone lines into high-speed data conduits
• Like dial, cable, wireless, and T1, DSL by itself is a transmissiontechnology, not a complete end-to-end solution
• End-users don’t “buy” DSL, they “buy” services, such ashigh-speed Internet access, intranet, leased line, voice, VPN,and video on demand
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DSL Modem TechnologyDSL Modem TechnologyDSL Modem Technology
• Trade-off is reach vs. bandwidth• Reach numbers are best-case assuming “clean copper”• Different Layer 1 transmission technologies, need a
common upper protocol layer to tie them together
DSL TechnologyDSL Technology Max. Data RateDown/Uplink (bps)
Max. Data RateDown/Uplink (bps)
Line CodingTechnologyLine CodingTechnology
BasebandVoice?
BasebandVoice?
VDSL –Very-High-Bit-Rate DSLVDSL –Very-High-Bit-Rate DSL
51-55M/1.6-2.3M13M/1.6-2.3M
51-55M/1.6-2.3M13M/1.6-2.3M TBDTBD YesYes
ADSL –Asymmetric DSLADSL –Asymmetric DSL
8M/1M1.5M/640K
8M/1M1.5M/640K
CAP, DMT,G.lite
CAP, DMT,G.lite YesYes
IDSL –ISDN DSLIDSL –ISDN DSL 144K/144K144K/144K 2B1Q2B1Q NoNo
SDSL –Symmetric DSLSDSL –Symmetric DSL
768K/768K768K/768K 2B1Q/CAP2B1Q/CAP NoNo
HDSL2 –High-Bit-Rate DSLHDSL2 –High-Bit-Rate DSL
1.5M-2M/1.5M-2M(T1-E1 Symmetric)1.5M-2M/1.5M-2M(T1-E1 Symmetric)
OPTISOPTIS NoNo
Max. ReachFeet (km)
Max. ReachFeet (km)
1,000 (0.3)4,500 (1.5)1,000 (0.3)4,500 (1.5)
18,000 (5.5)18,000 (5.5)
18,000 (5.5)+(w/repeaters)18,000 (5.5)+(w/repeaters)
22,000 (6.9)22,000 (6.9)
15,000 (4.6)15,000 (4.6)
Key AttributesKey Attributes
Very Fast—Short ReachNo Standard Yet
Very Fast—Short ReachNo Standard Yet
Coexists with POTSTechnology of Choice for
Residential
Coexists with POTSTechnology of Choice for
Residential
Uses Existing ISDN CPERelatively Slow
Uses Existing ISDN CPERelatively Slow
SymmetricNo standardSymmetric
No standard
Standard Still underDevelopment
Standard Still underDevelopment
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ADSL “Consumer DSL”ADSL “Consumer DSL”
• Designed to co-exist with POTS, unlike mostother DSL types
• “Slow” upstream for low-data-rate requests
• “Fast” downstream for bursts of rich graphicsand multimedia content
• Three basic “flavors” of ADSL(modulation techniques)
CAP (Carrierless Amplitude modulation/Phase modulation)
DMT (Discrete MultiTone modulation)
G.lite (Consumer/mass-market DMT)
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ADSL and POTSADSL and POTS
A Key Feature of ADSL Is Co-Existence with POTS
Customer Premise Central Office
DSLAMPOTSSplitter
Microfilter
POTS + ADSL ADSLADSL CPEPC
StandardAnalog Phone
DLC Class 5 Switch
AnalogVoice
NID
• Permits transmission of both signals on the same wire pair• Off-loads data circuit from the voice switch• “POTS Splitter” at the CO separates analog POTS from data• “Microfilters” at the customer premise prevent off-hook
interference between analog voice signal and ADSL signal
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G.liteG.lite“Mass-Market DSL”“Mass-Market DSL”
• Simplified DMT encoding scheme
• Limited “features” to facilitate broadinteroperability and minimizeend-user interaction
• No embedded management channel
• “Splitterless”
• Max. downstream data rate = 1.5 Mbps
• Max. upstream data rate = 640 kbps
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ADSL StandardsADSL Standards
• Full-rate DMTANSI T1.413—Issue 2
ITU G.992.1 (G.dmt)
ITU G.994.1 (G.hs)
• Consumer DMTITU G.992.2 (G.lite)
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InteroperabilityInteroperability
Why it’s good…• Enables competition and lower
equipment costs for serviceproviders and end-users
• Lower component costs forequipment manufacturers
• Proliferation of CPE optionsfor end-users
• Retail availability of CPE(consumer mass market)
Why it’s difficult…• Standard must specify
physical layer (at all datarates) and framing
• Value-added services requireLayer 2/3 implementations
• Standards developmenttakes time
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End-To-EndEnd-To-EndDSL Protocol StackDSL Protocol Stack
ATMBackbone
CPE AggregatorDSLAM Content Server
Layer 1Layer 1
Layer 2Layer 2
Layer 3Layer 3
ApplicationApplication
ATM
DSL
AAL5
PPP
IP
ApplicationProtocols
AAL5
PPP
ATM
IP
ApplicationProtocols
End-UserEnd-UserTelco
NetworkTelco
Network ISPISPContentProviderContentProvider
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The Epic Battle: DSL vs. CableThe Epic Battle: DSL vs. Cable
April 20, 1999
The Faster WebDSL, Cable, and Satellite
Editors’ Choice:Cable Modems
• Performance and new-world servicesdepend more on the network designthan the transmission technology
• Cable companies have an early lead
• The Telcos have awakened
Monday, May 24, 1999
DSL Beats Cable in Net SpeedServices Tested During ‘Rush Hour’
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DSL vs. Cable Bake-OffDSL vs. Cable Bake-Off
DSLDSL CableCable
Dedicated Vs. SharedDedicated Vs. Shared
DSL Is a Dedicated Connection:DSL Is a Dedicated Connection:• No bandwidth contention• Secure• No bandwidth contention• Secure
Cable Is a Shared Wire:Cable Is a Shared Wire:• Noticeable speed impairment
during “rush hour”• Near-term security issues
• Noticeable speed impairmentduring “rush hour”
• Near-term security issues
AvailabilityAvailability Telephone Wires Are UniversallyAvailable to Nearly Every Businessand Residence
Telephone Wires Are UniversallyAvailable to Nearly Every Businessand Residence
Existing Cable Is Almost ExclusivelyResidentialExisting Cable Is Almost ExclusivelyResidential
AccessibilityAccessibility Approx. 15% of Current CustomersAre Inaccessible (Out-of-reach,Bad Copper, Etc.)
Approx. 15% of Current CustomersAre Inaccessible (Out-of-reach,Bad Copper, Etc.)
Cable Head-end Equipment Must BeUpgraded or Replaced for Two-wayCommunication
Cable Head-end Equipment Must BeUpgraded or Replaced for Two-wayCommunication
ImpairmentSusceptibilityImpairmentSusceptibility
Cable Is Shielded—Signal Impairment Is Not a ProblemCable Is Shielded—Signal Impairment Is Not a Problem
CustomerSupportCustomerSupport
Established Customer SupportModels and Systems for DataServices and Per Subscriber Outages
Established Customer SupportModels and Systems for DataServices and Per Subscriber Outages
Data Service Is New and OperationsModel Is Broadcast OrientedData Service Is New and OperationsModel Is Broadcast Oriented
ConsumerAwarenessConsumerAwareness
Telcos Are the Incumbent for Voiceand DataTelcos Are the Incumbent for Voiceand Data
Cable Companies Are MovingAggressivelyCable Companies Are MovingAggressively
Telephone Wires Are Susceptible toHigh-frequency Cross-talk andExternal Impairment
Telephone Wires Are Susceptible toHigh-frequency Cross-talk andExternal Impairment
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Basic DSL Network ComponentsBasic DSL Network Components
DSL CPECustomer Premise EquipmentPC NICs, bridge/routers, enterprise routers
DSLAMDSL Access Multiplexer
Concentrates individual subscriber lines from CPE
Aggregator/service selection gatewayConcentrates ATM feeds (T-1, DS-3, OC-3) from DSLAMs
PPP termination, Layer 2 and 3 service selection
On-demand, personalized services
Accounting and billing
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Basic DSL Network TopologyBasic DSL Network Topology
Cisco2600/3600
Home Office,Telecommuter
Power Branch
Small-MediumEnterprise
Cisco 6400
ServiceSelectionGateway
PSTN
VVoiceGatewayCiscoAS5300
NetworkManagementandProvisioning
PacketBackbone
ATMBackbone
Residential
Cisco600
Cisco600/700/800/1000
LEC ISP
Enterprise
Home GatewayCisco 3600,6400, 7200
Internet
Home GatewayCisco 6400,
7200
• Local VoiceServices
• ManagedVoice andData VPNs
• AdditionalLinesOn-demand
• Private LineReplacement
• VideoConferencing
• Video onDemand
• High-speedInternetAccess
Mor
e B
andw
idth
= M
ore
Ser
vice
s =
Mor
e P
rofit
Opp
ortu
nitie
sM
ore
Ban
dwid
th =
Mor
e S
ervi
ces
= M
ore
Pro
fit O
ppor
tuni
ties
Cisco90iCisco90i
Cisco6100/6200Cisco6100/6200
Cisco1400/1700
Cisco 6400AggregatorCisco 6400Aggregator
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COCO
SuburbsSuburbs
CityCity
RTRT
Telephone CompanyTelephone CompanyDeployment OptionsDeployment Options
• Central officeLocate DSLAM in central offices(COs) for best coverage in cities,dense suburbs
• Remote terminalLocate DSLAM in unmanned remoteterminals (RTs) for expanded coveragein suburbs and rural areas—verycommon in new developments
• CollocationIn some countries, competitive carrierscan obtain CO space from incumbentcarriers and lease “dry” copper loopsto reach customers Suburbs,Suburbs,
RuralRural
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• DSL can be effective whereverthere is existing copper
• In-building networksLocated in the basement ortelco closet of hotels, apartmentbuildings, or office buildings
• Campus-style networksLocated centrally to servemulti-building campusnetworks, such as officeparks and apartment complexes
Private CopperPrivate CopperDeployment OptionsDeployment Options
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Voice overData
VideoConferencing
DistanceLearning
SecureVPN
InternetAccess
E Commerce
Today BusinessConsumer
New World ServicesNew World Services
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Price…and an Alternative to
Traditional AccessLoops for Lower Cost
Price…and an Alternative to
Traditional AccessLoops for Lower Cost
DSLAccessDSLAccess
ISPand/or
Enterprise
Dialup
PerformanceAlternative to PSTN/ISDN:High-Speed, Always-On
Network Access…
PerformanceAlternative to PSTN/ISDN:High-Speed, Always-On
Network Access…PSTNISDN
T1, DDS,nxDS0
Telecommuter
Residential
BranchEnterprise
Small-to-Medium-sized
Enterprise
Exploding DSL MarketplaceExploding DSL Marketplace
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Market DynamicsMarket Dynamics
Attack• CLECs are pursuing small
businesses that have hadonly limited data accessoptions
• T-1 service has been tooexpensive and an overkill
• ISDN is too slow
Attack• CLECs are pursuing small
businesses that have hadonly limited data accessoptions
• T-1 service has been tooexpensive and an overkill
• ISDN is too slow
Defend• ILECs are reacting to the
onslaught of cable modems
• Defending their residentialaccess franchise
• Off-loading internet datatraffic from the voicenetwork
Defend• ILECs are reacting to the
onslaught of cable modems
• Defending their residentialaccess franchise
• Off-loading internet datatraffic from the voicenetwork
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“
”
This Changes Everything…This Changes Everything…
Broadband Internet AccessThreatens POTS
Subscriber Loyalties ThatHave Withstood Decadesof Low-price Come-ons
302031085_06F9_c1 © 1999, Cisco Systems, Inc.
More, Better, Faster, CheaperMore, Better, Faster, Cheaper
• It’s no longer just about cheaper phone bills…
• Now it’s about high-speed Internet access…
• And, “Oh, by the way”, bundled voice lines…
• And, value-added voice/data/video services!
Consumer Proposition
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• DSL is ready for prime time!
• Data-traffic volumes are eclipsingvoice-traffic volumes on thepublic networks
• Carriers have tested DSL,and now need to scale formass deployment
• Profits in an era oflow-cost access will comefrom new- world services
SummarySummary
Data
Voice
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Session 203Session 203
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