3 Infrastructures 11

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Network Infrastructures – a.a. 2011-2012Lecture 3 pag. 1

Network Infrastructures

A.A. 2011-2012

Prof. Francesca Cuomo

2

Network functional areas




3

Access network

• An access network is that part of a communications networkwhich connects subscribers to their immediate serviceprovider

• It is contrasted with the core network

• The access network may be further divided between feederplant or distribution network, and drop plant or edgenetwork.

POP

Backbone

Access Node

Access Network

Metropolitan Area

4

Access network

• The access network domain plays an important role in anetwork by connecting communications carriers and serviceproviders with the individuals and companies they serve

• While communications carriers have historically used

“copper lines” to offer phone service to individualsubscribers, today the same line carries high-speedbroadband services such as DSL (Digital Subscriber Loopor Digital Subscriber Line) in addition to telephone signals

• Carriers are also investing heavily in optical fiber as thetransmission media for fixed broadband access

– due to its high-speed and stable transmission characteristics




5

Core Network

• A core network is a backbone network:

– usually with a mesh topology

– provides any-to-any connections among devices on the network

– consists of multiple switches (e.g., ATM- Asynchronous TransferMode) or consists of IP routers

– is constituted by an optical backbone

• The Internet could be considered a giant core network

– it really consists of many service providers that run their owncore networks, and those core networks are interconnected

• Significant to core networks is "the edge," wherenetworks and users exist

6

Edge of the network

• The edge may perform intelligent functions that are notperformed inside the core network.

– if the core network is using MPLS (Multiprotocol LabelSwitching), an edge switch may examine packets and select apath through the network based on various properties of the

packet• The core network then switches the packets (as

opposed to doing hop-by-hop routing of the packets),which significantly improves performance

– In this case, the core network is considered relatively "dumb"while the edge is considered "smart" because the path selectionthrough the core is determined by the edge




7

Access / Core network

PSTN/ISDN

ADSL

Copper

Cellular access

Fixedwireless

acces

Fiber

access

LAN

LAN

Core Network

GSM/UMTS

An example: Telecom Italia

BACKBONE NETWORK

IP-DSLAM(4.000)

HSPA / LTE / WIMAX

ADSL2+( ˜10Mbit/s)

//

OPTICALPACKET

BACKBONE

MSC.S

xGSN

RNC-UNC

DPI

BRAS

PE

OPTICALPACKETMETRO

FTTCVDSL2

( 50Mbit/s )

// IP-MSAN(ONU)

GPONHSPA / LTE / W IMAX

( ˜ 10 Mbit/s)

MULTISERVICEEDGE NODE

(POP)

RANCN

BBANEDGE

STORAGE

FTTH/ B(100Mbit/s )

FTTB

AREE METROPOLITANE

// //

//

REGIONAL/METROPOLITAN NETWORK

ACCESS NETWORK




Network Terms

• Exchange Area

– Local vs long distance

• LEC – Local Exchange Carrier

• ILEC – Incumbent LEC

• CLEC - Competitive LEC

• Trunks – fiber optical

• CO - Central Off ice

• LATA – Local access andtransport area

• IXC – Inter-exchange Carrier

– Carry inter-LATA traffic

9

Some examples

10

Collocation space to permit CLECs tolocate equipment in the central office

Distribution frame wherethe copper pairs areconnected one-by-one tothe Central Office




11

Distribution network

Telecom Italia access Network

12

Quantità Unità misura

Borchia d’utente 33.576.000 Numero di borchie

Distributore 3.893.000Numero di

distributori

Armadio ripartilinea 142.500 Numero di armadi

Cavi a coppie

simmetriche105.700.000 km - circuito

Cavi (tracciato) 575.000 km

Palificazioni 8.893.000 Numero di pali

Infrastrutture di posa 20.000 km - tubazioni

Fonte: Telecom Italia 2007




13

Fixed Line Access Network

• An access network refers to the series of wires, cables and

equipments lying between a consumer/business telephonetermination point (the point at which a telephone connectionreaches the customer) and the local telephone exchange

• The local exchange contains banks of automated switchingequipment to direct a call or connection to the consumer

• The access network is perhaps one of the oldest assets atelecom operator owns, and is constantly evolving, growing

as new customers are connected, and as new services areoffered

• This makes the access network one of the most complex

networks in the world to maintain and keep track of

14

Fixed Line Access Network

• The access network is also perhaps the mostvaluable asset an operator owns, since this iswhat physically allows them to offer a service

• Access networks consist largely of pairs of

copper wires, each traveling in a direct pathbetween the exchange and the customer

• Access networks around the world evolve toinclude more and more optical fiber technology

• Optical fiber already makes up the majority ofcore networks, and is now closer and closer tothe customer (e.g., FTTH Fiber To The Home )




15

Local loop

• In telephony, the local loop (also referred to as asubscriber line) is the physical link or circuit, thatconnects from the demarcation point of thecustomer premises to the edge of the carrier ortelecommunications service provider, network.

• At the edge of the carrier network in a traditionalPSTN (Public Switched Telephone Network)

scenario, the local loop terminates in a circuitswitch housed in an ILEC Central Office.

16

Local loop

• Traditionally, the local loop was wireline in nature fromcustomer to CO, specifically in the form of an electricalcircuit (i.e., loop) provisioned as a single twisted pair insupport of voice communications

• Modern implementations may include a digital loop carrier

system segment or fiber optic transmission system knownas fiber-in-the-loop

• The local loop may terminate at a circuit switch owned bya CLEC and housed in a POP, which typically is either anILEC CO or a "carrier hotel"

• A local loop may be provisioned to support datacommunications applications, or combined voice anddata such as digital subscriber line (DSL)




17

Local loop

• Local loop connections can be used to carry a range ofservices, including: – analog voice and signaling used in traditional POTS – Integrated Services Digital Network (ISDN) – variants of Digital Subscriber Line (DSL)

• Many owners of local loops are public utilities that hold anatural monopoly

• To prevent the owner from using this natural monopolyto monopolize other fields of trade, some jurisdictionsrequire utilities to unbundle the local loop, that is, make

the local loop available to their competitors• The term "local loop" is sometimes used for any "last

mile" connection to the customer, regardless oftechnology or intended purpose. Hence the phrase"wireless local loop"

18

Local loop

• Local loop connections include:

– Electric local loop: PLC (power line communications)

– Optical local loop: Fiber Optics services

– Satellite local loop: communications satellite and

cosmos Internet connections of satellite television(DVB-S- Digital Video Broadcasting-Satellite)

– Cable local loop: Cable modem

– Wireless local loop (WLL): LMDS, WiMAX, GPRS,HSDPA, DECT

LMDS: Local Multipoint Distribution ServiceGPRS: General Packet Radio ServiceHSDPA: High Speed Downlink Packet Access




19

Type of access

• Copper access :

– This domain provides both high-speed broadbandand existing phone service.

» VDSL solutions that support high-speed broadband service

» phone migration solutions that can deliver existing phoneservice quality as a key infrastructure even as it evolvestoward an IP network.

VDSL: Very High Digital Subscriber Line

20

Copper based access network

• The major advantage of this network is that it is widely available

– In industrialized countries there is almost universal access to thisnetwork, and in all countries the network can be accessed in the majorcities

– In those areas, use of existing infrastructure facilities is still verycompetitive in providing most types of services

– In areas not covered by copper-based networks, use of other networktechnologies is likely to offer a cost efficient alternative

• The network is usually operated by the incumbent operator, which inmany cases is fully or partly owned by the public

• The copper-based networks are established in markets withmonopoly, and are therefore designed for covering the entire market

• Efforts have been made to introduce competition through demandsfor unbundling of facilities and interconnection with other networks




21

Copper based access network

• Existing copper-based networks have gradually beenexpanded during several decades and their architecturesare not optimized with regard to use of currenttechnologies

• If an entirely new network were to be built today, it wouldnot be based on use of copper-based technologies, andthe design would therefore be very different from thoseof today’s copper-based networks operated by theincumbent operators

• One problem is that networks are designed mainly for

carrying POTS, while a growing share of the traffic isbased on IP or other data communication protocols, andin some areas there are problems with capacity andquality of service.

22

Cost analysis

• Access costs constitute 35-50% of the total networkcosts.

• Here the major cost driver is total cable length, whichagain depends on the number of connections and thedensity of customers.

• It may cost as much as five times more to connectcustomers in rural areas than in metropolitan areas.

• A major part of the costs are related to the laying ofcables underground. Here substantial savings can beobtained through the use of ducts that can be sharedbetween several cables.

• The digging costs are highly dependent on the geo-types. – it should be noted that digging costs per km often are much

higher in metropolitan areas than in the open land.




23

Cost analysis

• The costs of copper-based networks are affected by the

following technological advances:

– Today the copper-based trunk network is replaced by an opticalnetwork, while the access network is still based on copper lines.Installation of fibers has reduced the cost of capacity in trunknetworks considerably

– Digitalization of switching facilities and use of packet switchedtransmission technologies has reduced switching costs.

– Implementation of Next Generation Access Network

technologies will reduce transmission costs even further – Altogether these trends imply that the cost of the copper-based

access network constitutes a still larger share of the totalnetwork costs

24

Cost analysis

• However, technological advances are also taking in thispart of the network.

• Alternative access networks offering lower costs orhigher capacity have been developed.

• In areas where investments in copper-based accessnetworks have already been made, the development oftechnologies offering more capacity on existing accessfacilities is at least as important.

• It is possible to upgrade the copper-based accessnetworks to carry high-speed services through the use ofxDSL technologies; the possible capacity depends onthe length of the copper cables and the quality of thenetwork.

• The bandwidths offered here range from 128 kbps to 10Mbps.




25

Cost analysis

• xDSL is the most widespread access technology for

broadband access as 57% of all broadband connectionsuse xDSL (end 2003).

• Provision of higher bandwidth will often, but not always,require more investments in the access network, and ofcourse more capacity in the core network.

• By all means, the capacity is much lower than in opticalnetworks.

• On the other hand, the additional investments neededfor upgrading the network are only a fraction of what isneeded for the establishment of an optical network.

26

Type of access

• Optical access :

– This domain will be the

mode of choice for fixedaccess in the coming years

» GE-PON (individual),» GPON (enterprise),

» and COF (long-distance)

» represent systems capableof delivering ultra-high-speed, high-reliabilityperformance.

GE: Gigabit EthernetPON: Passive Optical NetworkCOF: Code Division Multplexing over Fiber




27

FTTx = Fiber-to-the-x

• FTTH - Home

• FTTC - Curb

• FTTN - Node or Neighborhood

• FTTP - Premise

• FTTB - Building or Business

• FTTU - User

• FTTZ - Zone• FTTO - Office

• FTTD - Desk

FTTx: reference architectures

• FTTx elements:

– OLT: Optical Line Terminal

– ONU: Optical Network Unit

– ONT: Optical Network Termination (NT: Network termination)

– ODN: Optical Distribution Network

28

ONU

ODNcp

OLT

:

O

NU

ON

U

ONU

splitter

NTxDSL

xDSL





• AON (Active Optical Network), also called Point-to-Point (P2P)

29


• PON (Passive Optical Network):passive branching of fibes via optical spilttersand tree-based topologies

30




FTTE/FTTCab/FTTCurb

• Fiber to the Exchange: the optical fiber terminates to the Central Office(CO) and the CO is connected with the user via a copper based line (e.g.,ADSL)

F.O.

Copper (ADSL)

Copper (VDSL)

ONU

F.O.

FTTEFTTE

FTTCabFTTCab:: the ONUthe ONU isis inin

thethe CabinedCabined

ONU

F.O. Copper (VDSL)

1,2-1,5 km*

FTTCurbFTTCurb:: the ONUthe ONU isis inin

thethe CurbCurb

CO

200-300 m*

50-150 m*

*Telecom Italia

31

FTTP/FTTB/FTTH

• Fiber to the Premises the fiber cables arrive to the users’premises

– Fiber to the Building

– Fiber to the Home

F.O.

FTTBFTTB

FTTHFTTH

VDSL, Ethernet, Wireless

F.O.

F.O.

F.O.

CO

ONU

Optical element

ONT ONT

32




VDSL2

Exchange Cabinet Curb Premises

C u r r e n t t e l c o

b r o a d b a n d

F T T C a b

F T T C u r b

F T T H ONT + set-top

+ home GW

DSLAM / ATM

aggregation

Aggregation

Aggregation

OLT

DSLAM

ONU

DSL modem

DSL modem +set-top +home GW

DSL modem +set-top +home GW

ONT + set-top+ home GW

VSDL/VDSL2

ADSL/ADSL2+

GE/EPON/GPON

Fiber Copper

E . g .

T e l e c o m

I t a l i a

a c c e s s n e t w o r k

(~10K) (~140K) (~5M) (~22M)

GE/EPON/GPON

1-1,2 km 200-300 m 50-70 m

1,2-1,5

km

Wireline access

33

Bandwidth requirements

34

Mbit/sMbit/sMbit/sMbit/s DownstreamDownstreamDownstreamDownstreamUpstreamUpstreamUpstreamUpstream

1.1.1.1.yyyy1.1.1.1.yyyy

Web surfing

Video communication

SDTV VoD

Peer-to-peer, File sharing

SDTV Live

Web Hosting

Telemedicine

HDTV VoD

Remote Storage

Next Generation 3D TV

ADSL/2+

FTTCab VDSL2

FTTB VDSL2

Gaming, Distance learning

FTTH

5555 10101010 20202020 50505050 1001001001005555101010102020202050505050100100100100

Source:Telecom Ital ia




Fiber based access network

35

36

Type of access

• Wireless access :

– This domain enjoys the highest

expectations from thestandpoint of ubiquitous

networking» WLL

» 3G mobile networking

» WiMAX solutions

» support seamlesscommunications and high-speedbroadband service, providingboth fixed and mobile access in asingle system




2G and 3G architecture

37

VLR

HLRHLR

RNC area

Node B

MS (ME+USIM) cell

RNCSGSNGGSN

HLR

Iu (PS)Gn

Iub

Iu (CS)

Uu

Iu (CS)

IurBSC

BSC

8.000 macro Node B

50 micro Node B

70 RNC

463 BSC

13.863 macro BTS

1.150 micro BTS

MSC

MSC

GSM network

38


Siti per antenne

radiomobili14.000 Siti dei tralicci

Stazioni radioBTS 13.865 Numero stazioniradio

Controllori

stazione BSC463 Numero di BSC

Trasmettitori 90.090 Numero di TXT

Celle 24.522 (900 MHz) – 7.551 (1800 MHz) Numero di celle

Canali556.264 (900 MHz) – 164.458 (1800

MHz)Numero di canali

Frequenze 12 (900 MHz) – 15 (1800 MHz) MHz




3G network

39


Siti per antenne UMTS 8.030 Siti dei tralicci

Stazioni radio - Nodi B 8.030 Numero stazioni radio

Controllori stazione

RNC70 Numero di RNC

Celle 22.094 Numero di celle

Canali 834.752 Numero di canali

Frequenze 10 (2100 MHz) MHz

Wireless Access: cont’d

40




Wireless Access: cont’d

• As ubiquitous service-anytime, anywhere, anyone-becomes thenorm, demand for technologies such as conventional cellularphone service and wireless LAN access is being augmented by anincreasingly noticeable desire for mobile high-speed broadbandservice and otherwise seamless communications 41

Techologies and bandwidths

42

TimeTimeTimeTime

~64 kbps

~256÷640 kbps

~2÷6Mbps

ADSL2+ADSL2+ADSL2+ADSL2+

VDSL2VDSL2VDSL2VDSL2

~10÷20 Mbps

ADSL freeADSL freeADSL freeADSL free

Dial UpDial UpDial UpDial Up

~50÷100 Mbps

ADSL flatADSL flatADSL flatADSL flat

~10 kbps

~100 kbps

HSPA 2HSPA 2HSPA 2HSPA 2

HSPA 2 +HSPA 2 +HSPA 2 +HSPA 2 +

~14 Mbps

HSPA 1HSPA 1HSPA 1HSPA 1

EDGEEDGEEDGEEDGE

UMTSUMTSUMTSUMTS

GSMGSMGSMGSM

~7 Mbps

~300 kbps

~ 3 Mbps




Backbone: the logical topology

43

OPB (Optical Packet Backbone)

•32 PoP

•Inner Core: 4 PoP (2 in Rome,, 2 inMilan)

•Outer Core: 28 PoP

•Inner Core: 10 Gbit/s (STM-•64)•Outer Core: 10 Gbit/s (STM-64),

•2,5 Gbit/s (STM-16) and 155 Mbit/s(STM-1)• Link used at 50%

Source: Telecom Italia

Backbone: the physical topology

44Source: Telecom Italia

Physical networkbuild up on theOptical TransportNetwork




Technologies and protocols

45

Synchronous Digital Hierarchy(SDH)Wavelength Division Multplexing(WDM)

Asynchronous Transfer Mode(ATM)Gigabit Ethernet (GbE)

Multi Protocol Label Switching(MPLS)

Layer 3

Layer 2

Layer 1

46

Towards the Next Generation Network




47

Example of network (next generation)

www.oki.com/en/NGN/solution/access_network.html

48

Example of access network connectivity

AGW : Access GatewayBS : Base Station

BTS : Base Transceiver Station

HGW : Home GatewayMC : Media Converter

MS : Mobile StationOLT : Optical Line Terminal

ONU : Optical Network UnitRNC : Radio Network Controller

SS : Subscriber Station

STB : Set Top Box




49

Next generation: wireless domain

• WiMAX (Worldwide Interoperability forMicrowave Access) – Can implement communications by both mobile

handsets and fixed terminals (IEEE 802.16ecompliant)

– Supports seamless communications at home,outdoors, at the office, etc.

– Enables high-speed data transmission compared to

3G (an international cellular phone standard)networks

– Enables high-quality transmission with QoS controlcompared to Wi-Fi

50

Next generation: optical domain

• GE-PON system GE-PON II system (GigabitEthernet-Passive Optical Network)

– GE-PON : High-speed, bidirectional communicationsat 1 Gbps

– Allows the cost of fiber to be dramatically reduced – Provides assured communications quality with QoS

control and streamlined maintenance with remoteaccess.

– Enables more flexible route design due to expandedfiber loss budget and support for up to 64 branches(GE-PON II only)




51

Next generation: optical domain

• GPON (Gigabit Passive Optical Network) – ITU-T G.984 Series compliant optical access system with

speeds of 2.5 Gbps down and 1.25 Gbps up

– Supports full TDM, ATM, and Ethernet signal service

– Can be used to provide high-reliability systems with 50-msredundancy switching and other features

• COF (Code Division Multiplexing on Fiber Optical,access system using code division multiplexing) – Proprietary access multiplex transmission technology using the

CDM coding scheme popularized by cellular phones

– Can guarantee 100M Ethernet bandwidth while assuring inter-channel security. Supports multiplexing of up to sixteen 100MEthernet signals and 1-wire bidirectional transmission using asingle wavelength.

52

Next generation: copper

• VDSL

– Supports VDSL (5-band) communications at speeds

of 100 Mbps down and 40 Mbps up

– Features QAM modulation to deliver low latency

compared to other modulation schemes – Center equipment features a compact 8-port design

that can be installed in even cramped settings wherespace is at a premium



Gartner hype cycle

53

Gartner hype cycle 2011

54

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