6.978/esd.68 competition in access networks...1 (physical layer unbundling) dark fiber leasing, or...
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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
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