6.978/ESD.68Competition in Access

NetworksSharon E. Gillett, MIT

The past: Silos

Broadcast

radio

Copper

POTS Cable TV

Coax

TV

Figur e 1: Past industry struc ture of resid ential access.

From (Clark, 1999)

The present: “Convergence”

TV

Copper

POTS Internet

IAP

CLEC

Coax Wireless Satelli te

radio

Figur e 2: Emerging indus try structure of residen tial acc ess

VDSLADSL

HFC

Broadcast

From (Clark, 1999)

The Future(?): Internet as Platform

Copper

POTS

Coax

Internet

IAP

Wireless Satelli te

radioPhone TV WebE-mail

Figur e 4: Poten tial indus try struc ture surround ing the Internet.

ADSL HFC

From (Clark, 1999)

Wireless Telephony Competing With Fixed Lines, 2002

0

20,000,000

40,000,000

60,000,000

80,000,000

100,000,000

120,000,000

140,000,000

160,000,000

180,000,000

200,000,000

1990 1991 1992 1993 1994 1995 1996 1997 1998 1999 2000 2001 20020

20,000,000

40,000,000

60,000,000

80,000,000

100,000,000

120,000,000

140,000,000

160,000,000

180,000,000

200,000,000

Acc

ess

Line

s

Num

ber o

f Sub

scrib

ers

3 mil

Fixed Lines(1) Wireless(2) Broadband(3) Cable Telephony(4)

(1) 1990-1998 data from “FCC Trends in Telephone Service May 2002”; 1999-2002 data from “FCC, Local Telephone Competition: Status as of Dec 31 2002”; (2) CTIA Semi-Annual Wireless Industry Survey, published 2003; (3) 99-2001:FCC.COM: Trends in Telephone Service May 2002 (High Speed Lines with 200Kbps in at least one direction; Legg Mason Wood Walker, Inc. "Coming Down the Pipe - Interim Report 4Q 2002/1Q 2003 Industry Update - March 13, 2003“; (4) NCTA, "Residential Cable Telephony Subscribers”

0

5

10

15

20

25

30

Denmark

Netherl

ands

Icelan

dKore

aSwitz

erlan

dFinl

and

Norway

Sweden

Canad

a

United

Kingdo

mBelg

iumUnit

ed Stat

esJa

pan

Luxe

mbourg

Austria

France

Austra

liaGerm

any

Spain

Italy

Portug

alNew

Zealan

d

Czech

Rep

ublic

Irelan

dHun

gary

Poland

Turkey

Slovak R

epub

licMex

icoGree

ce

Source: OECD

DSL Cable Other

OECD Broadband subscribers per 100 inhabitants, by technology, June 2006

OECD average

Courtesy of OECD. Source: OECD Broadband Statistics, http://www.oecd.org/sti/ict/broadband. © OECD, 2006.

7

3. Broadband Technologies

Courtesy of CSTB. Used with permission.

8

Network Architecture

• Generic model of a broadband access network• system architecture common across technology alternatives• important differences in cost-performance and business models

INTERNETINTERNET

Web Servers, etc.

Access Router/Headend/Cache

Consumer Equipment(wired & wireless)

SubscriberInterface Access

Medium(copper, coax,fiber, wireless)

Multiplexedbroadband pipew/ aggregated data

IP packets

may be sharedor switched

IP packets

technology-specificpart of the system

Courtesy of CSTB. Used with permission.

9

Wireline Options• Hybrid fiber-coax

– DOCSIS– Role of fiber (toward FTTC)

• Digital subscriber line (DSL)– Distance, crosstalk– Role of fiber (toward FTTC)

• Optical fiber– Flavors of fiber to the home (FTTH)– Service based on equipment at both ends

• Depends on what “kind of “ FTTH: not all the same– High-performance endpoint—highest cost

• Powerline

Courtesy of CSTB. Used with permission.

10

DSL/Fiber Architecture• Same architecture evolves naturally from ADSL to

VDSL to FTTC/FTTH• switching equipment tends to migrate closer to subscribers

(..remote DSLAM, gigabit Ethernet switches, etc.)• system deployment cost dominated by physical wiring, due to

rapid improvements in switching & transport cost/performance

Access Switch/Router w/ caches

DSLAM orFiber Switch/Concentrator

High-capacity fiber link(ATM or IP/SONET, etc.)

SubscriberInterface may be placed

in remote locationor central officein-home

or curbside

to multipleISP’s

fiber orcopperpair

Courtesy of CSTB. Used with permission.

11

HFC Architecture• Broadband access over cable based on shared

access (DOCSIS standard) to existing TV coax• Medium access control (MAC) protocol for coax sharing • Signal converted to analog fiber at remote node• System cost dominated by fiber upgrade investments, due to

rapidly falling cost of DOCSIS modems & switching gear• Also evolves naturally towards FTTC/FTTH

IP Router &cache

Cable Modem

FiberNode HFC Analog Fiber Link

at remote locations

in-homesharedcoax cable

DOCSISprotocols

data downstream

TV

data upstream

Aggregated traffic

DOCSIShead-end to Internet

Courtesy of CSTB. Used with permission.

One Architecture for BPL

IPL-modem

Backbonenetwork/Internet

Tr

O/E

Distributionsubstation

CustomerLV networksOptical fibernetworks

IPL LANPoint-to-pointLink

13

Wireless Options

• Mobile/3G– Future: seamless mobile & portable broadband– Reality: emerging 3G falling short of hype (capacity, speed..)

• WLAN– 802.11, unlicensed 2.4 and 5 Ghz bands– Bottom-up deployment is accelerating... (airports, offices, homes..)

• FWA (Fixed Wireless Access)– MMDS, LMDS,...– much potential, but uncertain business conditions ...

• Satellite– Geo-synchronous (GEOS) & Low-earth orbit (LEOS)– Viable for certain markets, but with capacity limitations...

Courtesy of CSTB. Used with permission.

14

Wireless Architecture• Broadband wireless based on shared access of

radio medium (MMDS, LMDS, 3G, WLAN,..)• MAC protocol for shared use of radio (..similar to cable modems)• Switching or routing beyond access point (...similar to DSL)• FWA, satellite, WLAN & 3G/mobile as potential options, each

with different entry cost and system cost/performance trade-offs

WirelesssubscriberInterface

Fixed Wirelessor satellite

WirelessAccess Point

at remote locationor CO

sharedwirelessmedium

High-capacity fiber link(ATM or IP/SONET, etc.)

radio“cell” forspatialreuse

Mobile Wireless(2.5G, 3G)

WLAN

Access Switch/Router w/ caches

to multipleISP’s

Courtesy of CSTB. Used with permission.

15

Local Access Techs in Context

• Total cost and performance depends on more than just local access

• Local access aggregates traffic from multiple premises at POPs, funnels to higher-capacity links

• “Second mile” connects to upstream aggregation• Broadband providers pay for Internet transit service

or establish peering arrangements• Caches, service-supporting servers at POPs

Courtesy of CSTB. Used with permission.

Unbundling DSL

After Fryxell, Sirbu, and Wanichkorn, 1999.

Access to unbundled

loop (“Full”unbundling)

Access to “bitstream”

IPGateway

Router CallServer

ATMSwitch

DSLAM

DSLAM

. . .

To Interoffice Transport

IP-based Central Office

POTS Customer

Analog Lines

DSLLines

Figure by MIT OCW.

DSL Customer

Sub-loop Unbundling

•••

•••

Remoteelectronics

Lasertransmitter

and receiverFiber feeder

•••

Remoteelectronics

CentralOffice

Copper wirepairs

ADSL Spectrum Allocation (Line Sharing)

POTS

10 KHz 50 KHz 1 MHz

Up stream channel

Downstream channelBidirectional

Open Access and LayeringLayer: Municipality provides…0 Conduit and collocation facilities.

1 (Physical Layer Unbundling)

Dark fiber leasing, or perhaps, Optical Layer unbundling (CWDM or DWDM in PONs)

2 (Data Link Layer Unbundling)

Dark fiber and link-layer electronics at each end. For example, Ethernet-based VLAN, or ATM-based PVCs.

3 (Network Layer Unbundling)

Basic network service provided. For example, IP Layer 3 service over cable using policy-based routing to multiple ISPs

Regulatory DilemmaHeisenberg’s Uncertainty Principle:

Can’t observe situation without perturbing it

Fundamental Economics

Regulatory Assumption About Competition

Outcome

Sustainable Free market

Not sustainable Regulation stifles innovation, competition

Sustainable Government-sanctioned, unregulated monopoly

Not sustainable Necessarily regulated monopoly

Competition is not sustainable (no competitive equilibrium)

Competition is sustainable (competitive equilibrium exists)

Additional Tech Slides

Internet Access via Cable

Headend

IP router

TV channels

Data (LAN) channel

Rest of Internet

RF ModemTranslator

Data (LAN) channel

RF ModemTranslatorConverter Converter

IXC = Inter-eXchange

Carrier (longdistance

company)

•••

•••

LECswitching

officeinter-office transmission

"CITY"

LECswitching

office

LEC = LocalExchange

Carrier (localtelephonecompany)

IXCswitch

IXCswitch

Inter-exchange ("long distance") network

•••

•••

LECswitching

officeinter-office transmission

"CITY"

LECswitching

office

Local Loop Local Loop

Local LoopLocal Loop

Telephone Network Hierarchy

Twisted-pair copper loops dedicated to individual subscribers• Physical aggregation at “Central Office” (CO) via Main Distribution Frame• CO Switching: Access• IXC Switching: Tandem• Increasing aggregation at each level

Multiplexing and Concentration in CO Switch

••• TDM

600 subscriber

lines

8:1 concen- tration

600 subscribers(DS-3) 600 trunks

(5000 subscribers)port

•

•

•

port

20-port switch fabric

••• •

•

•

Splices represented by

Distribution cable

DropDrop

Distribution cable

DropDrop

JunctionBox

JunctionBox

Feeder cables

DropDrop

Distribution cable

DropDrop

Distribution cable

towardCentralOffice

Telephone Access Network

• Feeder• Distribution• Drop• Aggregation is physical: bundles of wire-pairs

Internet over ADSL (with VoIP)

After Fryxell, Sirbu, and Wanichkorn, 1999.

Access to unbundled

loop (“Full”unbundling)

Access to “bitstream”

IPGateway

Router CallServer

ATMSwitch

DSLAM

DSLAM

. . .

To Interoffice Transport

IP-based Central Office

POTS Customer

Analog Lines

DSLLines

Figure by MIT OCW.

DSL Customer

Telco migration to Fiber-to-the-Neighborhood

•••

•••

Remoteelectronics

Lasertransmitter

and receiverFiber feeder

•••

Remoteelectronics

CentralOffice

Copper wirepairs