introduction to xdsl technology
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Introduction to xDSLIntroduction to xDSLTechnologyTechnology
Session 203Session 203
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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 achieve
megabit-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-bandmodem 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
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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
ServiceService
Leased 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 Residential
Broadband Important?Broadband Important?
Fast downloads ofrich content
Graphics, animation, audio,and video
Always onConstant interaction with amultitude of network-awareInternet 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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P
OT
S
P
OT
S
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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DSLModem
Value-AddedPacket
Network
End-User
DSLModem
DSL
Copper Loop
Enet 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 dont 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 acommon upper protocol layer to tie them together
DSL TechnologyDSL Technology Max. Data RateDown/Uplink (bps)
Max. Data Rate
Down/Uplink (bps)Line Coding
Technology
Line Coding
TechnologyBaseband
Voice?
Baseband
Voice?
VDSL Very-High-Bit-Rate DSL
VDSL 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 DSL
ADSL Asymmetric DSL
8M/1M1.5M/640K
8M/1M1.5M/640K
CAP, DMT,G.lite
CAP, DMT,G.lite
YesYes
IDSL ISDN DSL
IDSL ISDN DSL 144K/144K144K/144K 2B1Q2B1Q No
No
SDSL Symmetric DSL
SDSL Symmetric DSL
768K/768K768K/768K 2B1Q/CAP2B1Q/CAP NoNo
HDSL2 High-Bit-Rate DSL
HDSL2 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. Reach
Feet (km)
Max. Reach
Feet (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 FastShort ReachNo Standard Yet
Very FastShort 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 standard
SymmetricNo standard
Standard Still underDevelopment
Standard Still underDevelopment
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ADSL Consumer DSLADSL 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-hookinterference between analog voice signal and ADSL signal
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G.liteG.lite
Mass-Market DSLMass-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 DMT
ANSI T1.413Issue 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 its good Enables competition and lower
equipment costs for serviceproviders and end-users
Lower component costs forequipment manufacturers
Proliferation of CPE options
for end-users
Retail availability of CPE
(consumer mass market)
Why its difficult Standard must specify
physical layer (at all datarates) and framing
Value-added services requireLayer 2/3 implementations
Standards development
takes 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-User TelcoNetworkTelcoNetwork ISPISP ContentProviderContentProvider
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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 services
depend 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
DedicatedVs. Shared
DedicatedVs. 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 impairmentduring rush hour
Near-term security issues
Noticeable speed impairmentduring rush hour
Near-term security issues
AvailabilityAvailability Telephone Wires Are UniversallyAvailable to Nearly Every Business
and Residence
Telephone Wires Are UniversallyAvailable to Nearly Every Business
and Residence
Existing Cable Is Almost ExclusivelyResidential
Existing 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-way
Communication
Cable Head-end Equipment Must BeUpgraded or Replaced for Two-way
Communication
ImpairmentSusceptibility
ImpairmentSusceptibility
Cable Is Shielded
Signal Impairment Is Not a Problem
Cable Is Shielded
Signal Impairment Is Not a Problem
CustomerSupport
CustomerSupport
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 Oriented
Data Service Is New and OperationsModel Is Broadcast Oriented
ConsumerAwareness
ConsumerAwareness
Telcos Are the Incumbent for Voiceand Data
Telcos Are the Incumbent for Voiceand Data
Cable Companies Are MovingAggressively
Cable Companies Are MovingAggressively
Telephone Wires Are Susceptible to
High-frequency Cross-talk andExternal Impairment
Telephone Wires Are Susceptible to
High-frequency Cross-talk andExternal Impairment
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Basic DSL Network ComponentsBasic DSL Network Components
DSL CPE
Customer Premise Equipment
PC NICs, bridge/routers, enterprise routers
DSLAMDSL Access Multiplexer
Concentrates individual subscriber lines from CPE
Aggregator/service selection gateway
Concentrates ATM feeds (T-1, DS-3, OC-3) from DSLAMsPPP 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
Network
Managementand
Provisioning
PacketBackbone
ATMBackbone
Residential
Cisco600
Cisco
600/700/800/1000
LEC ISP
Enterprise
Home GatewayCisco 3600,6400, 7200
Internet
Home Gateway
Cisco 6400,7200
Local VoiceServices
ManagedVoice andData VPNs
AdditionalLinesOn-demand
Private LineReplacement
VideoConferencing
Video onDemand
High-speedInternetAccess
MoreBandwid
th=MoreServices=MoreProfitOpportunities
MoreBandwid
th=MoreServices=MoreProfitOpportunities
Cisco
90i
Cisco
90i
Cisco
6100/6200
Cisco
6100/6200Cisco1400/1700
Cisco 6400Aggregator
Cisco 6400Aggregator
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COCO
SuburbsSuburbs
CityCity
RTRT
Telephone CompanyTelephone Company
Deployment OptionsDeployment Options Central office
Locate DSLAM in central offices(COs) for best coverage in cities,dense suburbs
Remote terminal
Locate DSLAM in unmanned remoteterminals (RTs) for expanded coveragein suburbs and rural areasverycommon 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 networks
Located in the basement ortelco closet of hotels, apartmentbuildings, or office buildings
Campus-style networks
Located 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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Priceand an Alternative to
Traditional AccessLoops for Lower Cost
Priceand 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 AccessPSTNISDN
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 too
expensive and an overkill ISDN is too slow
Attack CLECs are pursuing small
businesses that have hadonly limited data accessoptions
T-1 service has been too
expensive 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 EverythingThis Changes Everything
Broadband Internet AccessThreatens POTS
Subscriber Loyalties ThatHave Withstood Decades
of Low-price Come-ons
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More, Better, Faster, CheaperMore, Better, Faster, Cheaper
Its no longer just about cheaper phone bills
Now its 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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