Network Infrastructures

Transcript

Network Infrastructures
A.A. 2014-2015
Prof. Francesca Cuomo
Towards Fiber to the X (FTTX):
Passive Optical Networks
Francesco Matera
Responsabile Area Tecnologie
Reti di Nuova Generazione
[email protected] ; +39 06 5480 2215
Network Infrastructures – a.a. 2008-2009
Lecture 0
pag. 1
Outline
•
•
•
•
Why FTTx
How FTTx: PON
Principles of Optical Fibre Systems
PON characteristics (APON, BPON, EPON,
GPON)
• Future: WDM PON
• Application
• Market (cost, unbundling)
Main source: Project EU E-Photon/One+, Lessons from Prof. A. Pattavina, G. Maier, Politecnico di Milano
Access/backhoul
10 Gbps
Fiber
1 Gbps
Optical
Wireless
100 Mbps
Microwave
10 Mbps
LMDS
1 Mbps
xDSL
50 m
200 m
Lecture 0
500 m
1 km
5 km
15 km+
pag. 2
PSTN access-network
Physical architecture
 Primary network
• High sharing
• Cost minimization
Distribution point
(box)
Distribution
cabinet
Primary cable
 Secondary network
• Flexibility
• Branching
Dedicated /
leased line
Twisted pair
Central office
 Cables
Secondary cable
• Primary


2400-2000 pairs
In duct or pipe
• Secondary


Feeder / primary
network
Distribution /
secondary
network
Home
network
100-10 pairs
Trenched or aerial
 Cascading more stages of cabinets
is possible but rare
Telecom access networks
Lecture 0
pag. 3
Optical Fiber: Attenuation

Single Mode Fiber (SMF) to achieve large distances
•
ITU G.652 SMF (STD)
•
ITU G652c/d SMF (ZWP)


“water peak” attenuation renders the 1360nm–1480nm spectrum unusable for data transmission
“zero-water peak”
3.0
First
Window
ATTENUATION (dB/km)
2.5
STD SMF
Second
Window
ZWP SMF
1310nm
Third
Window
2.0
1.5
850nm
1.0
1550nm
0.5
800
900
1000
1100
1200
1300
1400
1500
1600
1700
WAVELENGTH (nm)
Optical Fiber: Chromatic Dispersion
 Causes signal pulse broadening
Single-mode optical fiber
Shorter Wavelengths
Longer Wavelengths
Dispersion
Material
Dispersion
Total
Dispersion
+
1200
Zero at 1310 nm
1400
1600
Wavelength [nm]
Waveguide
Dispersion
Lecture 0
pag. 4
Lasers Diodes (LD)
Simple FP
+
 Fabry-Perot (FP)
gain
• Cheap
• Noisy

mirror
-

cleave
Sensitive to chromatic dispersion
• Used on 1310 nm
DFB
+
 Distributed Feedback (DFB)
• More expensive
• Narrow spectral width

gain
mirror
-

AR coating
Less sensitive to chromatic dispersion
• Used on 1550 nm (or 1310 nm)
Passive Splitters
 1xN Splitter
 1x2 Splitter
•
The basic element consists of two fibers fused together
•
Every time the signal is split two ways, the signal is reduced by 10log(0.5)=3dB
• Loss ~3dB x log2(#ONUs)
Splitter 1x2
Lecture 0
Conventional
Low-loss
3.7dB
3.4dB
pag. 5
Photodiodes (PD)
 PIN Photodiodes
• Good optical sensitivity (-22 dBm)
• Silicon for shorter ’s (eg 850nm)
• InGaAs for longer ’s (eg 1310/1550nm)
 Avalanche Photodiodes (APDs)
• Higher sensitivity (-30 dBm)
• Primarily for extended distances in Gb/s rates
• Much higher cost than PIN diodes
Transceiver Assumptions
TX Power
RX Sensitivity
ONU (FP+PIN)
0 dBm
-22 dBm
OLT (DFB+APD)
1 dBm
-30 dBm
 Upstream (@1310nm) Power Budget = 30 dB
 Downstream (@1490nm) Power Budget = 22 dB
Lecture 0
pag. 6
Fiber installation
La microtrincea come semplice ed economica soluzione per la diffusione della fibra ottica nella rete di accesso
(from HighBand)
30-40 K €/km per microtrincea
Soffiaggio della fibra (ERICSSON)
500-1000 m
100-300 m
50-200 m
Centrale
Cavo
Primo
Armadio
DSLAM
Secondo
Armadio
a) Best cuurent architecture
Primo
Armadio
Switch/ Fibra ottica
Router
Secondo
Armadio
DSLAM
b) Fiber to the cabinet
Lecture 0
pag. 7
Primo
Armadio
router
Secondo
Armadio
DSLAM
c) Fiber to the curb
Primo
Armadio
router
Secondo
Armadio
D
d) Fiber to the building
Primo
Armadio
router
Secondo
Armadio
e) Fiber to the home
Lecture 0
pag. 8
a)
b)
c)
Central
office
Central
office
Curb
switch
PON
Central
office
Splitter
ottico
Access capacities
Lecture 0
pag. 9
GbE based: FASTWEB
Daisy chain architecture
Core
First case in Europe:Fastweb 2000
FTTH: Accesso Residenziale
FTTB: Accesso Business
Uplink
Fibra
LAN
HAG
Technical room
Verso la
Backbone
IP switch
PABX
Router
Verso la
Backbone
Lecture 0
pag. 10
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
Basic PON operations
 The optical line terminal (OLT) broadcasts data downstream on 1,510 nm and
the ONTs burst data back upstream on 1,310 nm in their assigned time slots.
Lecture 0
pag. 11
Photonics Evolution
Optical Packet switching
FTTH
Optical burst switching
WDM
2015
2010
FTTH
VDSL2
FTTB
VDSL/2
2008
L1
Conversione lunghezza d’onda
Provider backbone transpoort
T-MPLS
GbE
FTTP
ADSL2+
10 m
100 m
VPLS
MPLS
1 km
10 km
100 km
Distanze
OTN
L2
SDH
L3
1000 km e
oltre
Time vs. Spectrum Sharing
 Downstream  point-to-multipoint network
• The OLT manages the whole bandwidth
 Upstream  multipoint-to-point network
• ONUs transmit only towards the OLT
• ONUs cannot detect other ONUs transmissions
• Data transmitted by ONUs may collide
Need of a channel separation mechanism to fairly share
bandwidth resources
TDMA
Time Division Multiple Access
Lecture 0
WDMA
Wavelength Division Multiple Access
pag. 12
PON Overview

TDM-PONs
•
•
•
•
Standardized
•
Traffic distribution
Use few wavelengths (typically 2 or 3)
Low cost and mature devices (splitters, lasers, etc.)
Limited power budget


•


Maximum distances  20km, Split ratios  64
Broadcast scheme in downstream
TDMA techniques in upstream
Examples: APON/BPON, EPON & GPON
WDM-PONs
•
•
•
•
Proposed in literature and/or demonstrated
Introduce WDM techniques and devices (AWG)
Long-reach and bandwidth
Examples: CPON, LARNET, RITENET, Success-DWA…
Downstream Traffic Scheduling
• OLT schedules traffic inside timeslots
-Time Division Multiplexing (TDM) scheme
• Time slots can vary from s to ms
A
A
B
C
B
A
OLT
B
C
B
B
Passive
Splitter
C
Lecture 0
pag. 13
Upstream Traffic
• All ONUs share the same upstream channel


ONUs cannot exchange data directly
Collisions may occur at the splitter/combiner
ONU
ONU
OLT
Passive
Splitter
ONU
Upstream Traffic Scheduling 2/4
• In general, PON standards propose Time Division
Multiplexing Access (TDMA) schemes

Upstream time slicing and assignment
ONU
A
B
C
B
B
OLT
B
ONU
Passive
Splitter
ONU
Lecture 0
pag. 14
Upstream Frame Reception
• The OLT receives frames with different powers


Much difficult to recover synchronism (clock and data recovery)
Burst Mode Receiver (complex) @ OLT
•
Sets 0-1 threshold on a burst basis
A
Automatic Gain Control
to adjust 0-1 threshold at
the beginning of each
received burst
7 km
B
OLT
B
A
B
3 km
Passive
Splitter
1 km
C
Evolution of the standards
10 GB EPON
Lecture 0
pag. 15
Fiber in the loop
PON standardization: a brief history

ATM PON (A-PON)
•
•
•
•
•
•

Traffic is carried using ATM raw-cell format and framing
1982: idea of PON (British Telecom)
1987 – 1999: PON testbeds by BT, Deutsche Telekom (Eastern Germany), NTT
(Japan), BellSouth (Atlanta, USA)
1995: 622 Mbit/s APON testbed (RACE BAF project)
1996: beginning of Full Service Access Network (FSAN) works
1997-’98: ACTS BONAPARTE and EXPERT/VIKING projects
Broadband PON (B-PON)
•
•
•
•
APON system is standardized by ITU-T with a new name to indicate that the
PON can offer full broadband service and not just ATM
Line rates: 155 Mbit/s symmetrical or 622/155 Mbit/s down/upstream;
ONU/OLT max distance: 20 km; max. # ONUs: 64
1998-’00: ITU-T G.983.1 (physical aspects) and G.983.2 (ONT management
and control)
2001-’02: other ITU-T G.983.x and Q.834.x, e.g.


G.983.4/.7: Dynamic Bandwidth Assignment (DBA), providing statistical multiplexing ( more users per ONU) and Quality of Service
(QoS) enforcement
G.983.3: adoption of WDM to increase capacity or to carry video signals
Fiber in the loop
PON standardization: a brief history
 Ethernet PON (EPON)
•
•
•
•
•
Traffic is carried using Ethernet framing
 Cheaper user equipment then BPON
 Ethernet much more widespread than ATM
Higher subscriber rates (up to 1.25 GbE symmetrical), 16 ONU (power budget)
2001: IEEE 802.3ah Study Group “Ethernet in the First Mile (EFM)”
First documents in Sept. 2003)
2004: final approval of Standard IEEE 802.3ah
 Gigabit-capable PON (G-PON)
•
•
•
•
Traffic is carried by using different possible framings: ATM (G.983 base) or via
G-PON Encapsulation Method (GEM), which can interface SDH (G.707 base) or
Ethernet (IEEE802.3 base).
Various line rates, up to 2.4 Gbit/s symmetrical, ONU/OLT max distance: 20
km; max. # ONUs: 64-128
2001: activity initiated by the FSAN group
2003: ITU-T G.984.x
Lecture 0
pag. 16
Ethernet Standards in EPONs
• EPON started to be standardized by IEEE 802.3ah EFM since 2001, it
was ratified in 2004
IEEE802.2 logical link control
IEEE802.1 bridging
IEEE802.3
Ethernet
MAC layer
IEEE802.4
Token bus
MAC layer
Physical
layer
Physical
layer
10Mb/s
IEEE802.5
Token ring
MAC layer
Physical
layer
100Mb/s
1Gb/s
Layer 2: data link layer
IEEE802.6
MAN
MAC layer
IEEE802.11
wireless
MAC layer
Physical
layer
Physical
layer
10Gb/s
Layer 1: physical layer
802.3ah
EFM
Ethernet PONs (EPONs)
 All packets carried in EPON are encapsulated in Ethernet frames
• Support for variable size packets
 Similar wavelength plan to BPON
 Maximum bit rate is 1Gbps MAC-MAC (1.25 Gbps at the physical layer with 8b/10b
line coding)
 Minimum number of splits is 16
 Maximum reach is
•
•
10 km (FP-LD @ ONUs, limited by dispersion in downstrea for G.652)
20 km (DFB-LD @ ONUs)
 Different configurations are allowed
Lecture 0
pag. 17
EPON Configurations
ONU
OLT
ONU
ONU
OLT
ONU
ONU
ONU
1) Tree Topology
ONU
(2) Ring Topology
OLT
ONU
ONU
ONU
ONU
OLT
ONU
ONU
ONU
(3) Tree with Redundant Trunk
(4) Bus Topology
EPON Downstream Traffic

Similar to a shared medium network

Packets are broadcasted by the OLT and selected by their destination ONU
1
1
ONU 1
1
3
1
2
1
OLT
3
1
2
Payload
Lecture 0
FCS
2
ONU 2
802.3 frame
Header
USER 1
USER 2
3
ONU 3
USER 3
pag. 18
EPON Upstream Traffic

ONUs synchronized to a common time reference

Centralized arbitration scheme OLT based

OLT grants access to ONU for a timeslot
•
Frames Buffer
1
Several Ethernet packets
1
1
3
2
3
3
1
ONU 1
USER 1
2
2
ONU 2
USER 2
OLT
Time slot
802.3 frame
3
3
3
ONU 3
Header
Payload
USER 3
FCS
The Multi-Point Control Protocol (MPCP)
 Original Ethernet MAC protocol cannot operate properly in the upstream channel
(no collision detection) since each ONU cannot hear other ONUs
 MPCP (Multi-Point Control Protocol) is a new function of the MAC control sublayer.
It is developed to support dynamic capacity allocation but the algorithms are an
equipment vendors choice (Dynamic Bandwidth Allocation - DBA)
• In-band signalling
• Messages (64 bytes)





GATE
REGISTER
REGISTER_REQUEST
REGISTER_ACK
REPORT
Octets
Octets within
frame
transmitted topto-bottom
Destination Address
6
Source Address
6
Length/Type 88-08
2
Opcode
2
Timestamp
4
Data/Reserved/Pad
40
FCS
4
LSB
MSB
b0
b7
Bits within frame
transmitted left-to-right
Lecture 0
pag. 19
Autodiscovery mode
 3 control messages:
• Register, start message sent by OLT;
• Register_Request, answer message from
not registered yet;
ONU
• Register_Ack,
message by OLT that allows
ONU registration.
GPON Standardization
ITU-T
Outline
Adoption
G.984.1
G-PON service requirements
(General characteristics)
Mar. 2003
G.984.2
G-PON Physical Layer spec.
(Physical Media Dependent (PMD) layer
specification)
Mar. 2003
G.984.3
G-PON TC layer spec.
(Transmission convergence layer specification)
Feb. 2004
Lecture 0
pag. 20
G.984.1 Service Requirements
Item
Target
Bit rates
1.25Gbit/s symmetric or higher (2.4 Gbit/s).
Asymmetric with 155/622Mb/s upstream
Physical reach
Max. 20 km or max. 10 km
Logical reach
Max. 60 km
Branches
Max. 64 in physical layer
Wavelength
allocation
Downstream: 1480 – 1500nm
Upstream: 1260 – 1360nm
Downstream video
wavelength (1550 –
1560nm) may be overlaid
GPON Encapsulation Mode (GEM)
 GEM provides a Generic Frame where to carry both TDM and packet traffic over
fixed data-rate channels
• Similar
Generic
SDH/SONET
Framing
Procedure
(GFP)
used
in
 A Generic Frame consists of:
• a core header
• a payload header
• an optional extension header
• a payload
• an optional frame check sequence (FCS).
Lecture 0
pag. 21
Downstream Frame Structure 1/3
 It consists of
• a Physical Control Block Downstream (PCBD)
• the ATM partition (N×53 bytes)
• the GEM partition
PCBd
n
Payload n
PCBd
n+1
Payload n+1
PCBd
n+2
TP-Frame = 125 µs
“Pure” ATM cells TDM & Data Fragments
Section
over GEM Section
N * 53 bytes
GPON Header
Lecture 0
pag. 22
Technical Standards Comparison
Technology
Standard
APON/BPON
(ATM PON/ Broadband
PON)
ITU-T G.983.x
GPON
(Gigabit PON)
ITU-T G.984
EPON
IEEE 802.3ah
(Ethernet PON)*
10GEPON
(10 Gigabit Ethernet
PON)
IEEE 802.3av
(Working
Task Force)
Downstream/
Upstream Bandwidth
155, 622 or 1244 Mbit/s
down
155 or 622
Mbit/s up
1.2 or 2.4
Gbit/s down
# ONT served
Limited by power
budget and ONU
addressing limits:
16 to 32 splitter
Lambda
1310 nm Up
1490 nm Down
Up to 64(physical)
1310 nm Up
Up to 128 (logical)
(1550 nm Down
for RF video)
Symmetric 1.25 Gbit/s
Up to 16
(symmetric 10 Gbit/s in
the future?)
Distance
ATM
20 km
GEM: G-PON
Encapsulation
Method (supports
Ethernet), ATM
10/20 km
(up to 60
km )
Ethernet
10/20 km
Ethernet
20 km
1490 nm Down
(1550 nm Down
for RF video )
155, 622, 1.2 or 2.4
Gbit/s up
10 Gbit/s down
1 Gbit/s up
Framing/
Protocol
1550 nm Down
1310 nm Up
1480-1500 nm
Down ?
32 (maybe more?)
1260-1360 nm Up
?
1550-1560 Video
overlay ?
Transmission Efficiency
1400
1200
scheduling OH : frame
delineation
1000
scheduling OH : PHY burst OH
scheduling OH : control
messages
Mb/s
800
payload encapulation OH
600
line coding
400
payload
200
0
EPON
Lecture 0
GPON
BPON
pag. 23
Header’s Comparison
24 bits
min.
4 bits
BPON
typ.
12 bits
EPON costs about ~10% the cost of BPON/G
typ.
8 bits
Guard Preamble Delimiter
Data
min. 76.8 ns
min.
typ.
typ.
25.6 ns 35.2 ns 16.0ns
GPON
Guard Preamble Delimiter
EPON
Data
max. 400 ns
max. 400 ns
Laser
turn on time
AGC, CDR
setting time
max. 400ns
Data
Laser
turn off time
Data
AGC: Automatic Gain Control; CDR: Clock and Data Recovery
Laser turn on time overlaps the laser turn off time of the previous burst
Simple WDM-PON
 Number of ONUs limited by wavelengths
 Point-to-point topology
 Long-reach (almost point-to-point reach)
OLT
ONUs
WDM Modulated
Source
WDM Receiver
Receiver
λ1
λ1, λ2….λn
λN+1
AWG
Transmitter
.
λN+1, λN+2….λ2N
1xN
λN
.
λ2N
Receiver
Array/Optical
Demux
Filter as Optical router
Receiver
Transmitter
Central Office (CO)
Lecture 0
pag. 24
Protection Mechanisms
OLT
TR
TR
TR
ONU-1
TR
ONU-2
・
・
TR
ONU-n
B type
1+1 protection of OLT
 Cost-effective
 Redundant feeder
 Redundant OLT transceivers
TR
OLT
TR
TR
ONU-1
TR
TR
ONU-2
TR
・
・
TR
ONU-n
TR
C type
1+1 protection of PON
 Most secure and expensive
 Redundant feeder and drops
 Redundant transceivers
Carrier Ethernet for PON (EPON)
Carrier Ethernet: Processing from level 3 to 2
Specific path for QoS
c)
Network
Central
office
PON
VLANTAG, VPLS, Q-in-Q, MAC in MAC, PBT
Lecture 0
pag. 25
Elements of a PON
Centrale
Rete Primaria
Rete Secondaria
Edificio
Sede d’Utente
Cabinet
VDSL
NT
Nodo
ATM
coppia inrame
VB5.1
VB5.2
F.O.
Diramatore
1:N
Rete CDN
V5.1
V5.2
STB
VDSL
F.O.
PSTN/ISDN
Curb
ONU
OLT
F.O.
NT
Rete Domestica
coppia inrame
Building
VDSL
ONU
NT
coppia inrame
OLT: Optical Line
VDSL: Very high bitrate Subscriber Loop
ONU: Optical Network Unit
NT : Network Termination
STB: Set Top Box
International development overview
 China
•
GPON and EPON are being tested in China : future PON growth mainly depends on Chinese market
evolution
•
Beijing, Wuhan, Shanghai e Guangzhou are the cities with the greatest FTTX deployment

Japan
• The number of xDSL users has decreased for the first time at the end of 2006, while FTTH users have
grown by 10% in 2006 last trimester.

South Korea
• In July 2007, 500.000 FTTH users
•
•
At the end of 2006, out of 26 million Broadband lines, FTTH accounted for 30% of the total amount.
Almost 4 million FTTB “apartment LANs”
Lecture 0
pag. 26
 USA
• Large average cable-length
• Large investments form cable operators, that account for a
relevant share of the broadband market
• No unbundling required for new fiber infrastructures.
 Brazil, Colombia, Argentina, Chile
• Less than 300.000 FTTH users
 Australia, New Zeeland, Kuwait, Russia, United Arab Emirates, Pakistan
• Less than 2 million FTTH users
Ref: EXFO, may 2007
•
Mostly in Northern Europe, local administrations are building the infrastructure, with equal
access conditions for service providers
•
The leading incumbents are deploying extended FTTCab/VDSL infrastructure plans.
•
•
•
•
•
Sweden: more than 500.000 FTTH users
France, UK: more than 600.000 FTTH users
Italy : more than 250.000 FTTH users
Denmark: more than 400.000 FTTH users
Holland : more than 500.000 FTTH users
Lecture 0
pag. 27
FTTx costs
FUB study on NGN economics
• 1400 Mega Euro for digital Divide end
(connection of central office to babckbone)
• FTTC/B/H for all? No 2 Mb/s for all but 20 Mb/s
for almost all and >50 Mb/s for many
• 10 million of users based on FTTB: total cost
15000 Mega Euro!
• Unbundling problems:
– For OLO no PON, yes Point-to-point
– We say yes PON since:
» with logical unbundling now and WDM later!
» Too cost to include devices in central office and fibres in
current ducts
» With PON we can shift OLO location from central office to
l
t b kb
Lecture 0
pag. 28
FUB Experiments on EPON
Roma – Pomezia
Anello Ottico 50 Km
single mode 1550 nm
Optical link 50 m
multi mode 850 nm
EPON
UP
1310 nm
DOWN 1490 nm
ATM DSLAM
NAS 3640
C1
Video Server
Doppino
telefonico
(ADSL)
ATM DSLAM
J1
Alcatel ESS 7450 xDSL Access J3
IP DSLAM
J4
Cisco 3640
FiberHome OLT e
ONU
Line
Simulator
C2
Anello ottico
sperimentale
Roma - Pomezia,
distanze variabili
tra 50 e 350 Km
Juniper M10 e M10i
Alcatel ESS 7450
Line
Simulator
xDSL Access J2
Fast Ethernet
Cisco 3845
Switch ATM
(SHDSL)
Line
Simulator
C3
OLT
xDSL Access ALCATEL
IPDSLAM 7324
(VDSL)
ONU2
ASAM 1000 e 7300
IP DSLAM
ONU1
ONU4
ONU3
FTTx Access (EPON)
Line
Simulator
xDSL Access (ADSL2+)
Logical network by means of
VPLS&VLAN Tagging
Un
generatore
traffico permette
congestionamento
PE2 e OLT
di
un
tra
Ethernet PON FiberHome
Lecture 0
pag. 29
Throughput in downstream
Congestione tra PE2 e OLT
Conclusions
• FTTx necessary for NGN
• PON is the best current solution
• Problems for investments and network
properties
Lecture 0
pag. 30

Network Infrastructures

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