Introduction to Xdsl Technology

8/14/2019 Introduction to Xdsl Technology

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Copyright 1998, Cisco Systems, Inc. All rights reserved. Printed in USA.1085_06F9_c1.scr 1

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1085_06F9_c1 1999, Cisco Systems, Inc. 1

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1085_06F9_c1 1999, Cisco Systems, Inc.

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1085_06F9_c1

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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Introduction to Xdsl Technology