Data Networks: Next-Generation Optical Access

toward 10 Gb/s Everywhere

Dr Kyeong Soo (Joseph) Kim (k.s.kim@swansea.ac.uk)

Multidisciplinary Nanotechnology Centre (MNC)

Outline

• Business and Architectural Issues

• Paradigm Shift in Optical Networking

• Ultimate Optical Network Architecture

• Toward Next-Generation Optical Access

• ECR-Based Quantitative Analysis Framework

• Summary

BUSINESS AND

ARCHITECTURAL ISSUES

Aim

• To identify promising routes forward in achieving the

goal of ―10 Gb/s everywhere‖, while making best use of

the existing knowledge in the literature and from earlier

projects.

– The solutions will show most promise of cost

effectiveness and power efficiency, and be future

proof (i.e., allowing bandwidth evolution and

infrastructure reuse).

Partners of Related Project

• 5 Industrial Partners

– Oclaro (Bookham)

– BT

– Ericsson

– CIP

– Gooch & Housego

• 4 Academic Partners

– Cambridge

– Essex

– Swansea

– UCL

Broadband Quality Score III Univ. of Oxford and Universidad de

Oviedo,

sponsored by Cisco

September 2010

The State of the Internet by Akamai

(2nd Quarter, 2010 Report)

FTTH* vs. Cloud Computing**

SaaS*** User

SaaS Provider/

Cloud User

Cloud Provider

Web Apps

Utility computing

vs.

* NGOA Workshop, Mar. 2008.

** “Above the clouds”, UC Berkeley.

*** SaaS: Software as a Service

FTTH Business Perspective*

Layer Economic

Character

Life Cycle Cost per

Subscriber

Service Layer Low CapEx,

average to high

OpEx

1 to x years ?

Active Layer Average CapEx,

low OpEx

5 to 10 years €300~500

Passive Layer High CapEx, very

(very) low OpEx

25 to 50 years €500~700

•NGOA Workshop, Mar. 2008.

Cloud Computing: New Aspects in Hardware*

• The illusion of infinite computing resources available on

demand

– Through the construction of large-scale, commodity-computer

datacenters at low cost locations, and virtualization technique

• The elimination of up-front commitment by Cloud users

– Companies can start small and increase gradually

• The ability to pay for use of computing resources on a

short-term basis as needed * “Above the clouds”, UC Berkeley.

Cloud Computing: Economic Benefits*

• Elasticity

– Ability to add or remove

resources at a fine grain

and with a small lead time

• Transference of risks of

– Overprovisioning

(underutilization)

– Underprovisioning

(saturation)

* “Above the clouds”, UC Berkeley.

Max. (=peak)

Min.

Avg.

Time

Demand

Cloud Computing: A New Killer Application for

Next Generation Optical Internet Access?

• Data transfer bottlenecks (to and from Clouds)

– Example: Move 10 TB from UC Berkeley to Amazon in

Seattle*

• WAN link of 20 Mb/s: 4 Msec ≈ 46 days

• Overnight shipping (FedEx): < 1 day (≈ 1.5 Gb/s)

• 10 Gb/s link: ≈ 2 hours

» Even better if we could use more than 10 Gb/s

for a short period!

* “Above the clouds”, UC Berkeley.

ULTIMATE OPTICAL NETWORK

ARCHITECTURE

Current Network Limitations

• Bandwidth-hungry services (e.g., VoD, IPTV):

– Increase the amount of network infrastructure

– Increase the network energy consumption

– Increase the data-driven network crashes

• Due to:

– Unbalance in capacity between core and access

– Mismatch between service/usage models and network

infrastructure

– Large number of power-hungry and error-prone electrical

components/systems

Paradigm Shift in Optical Networking

• Changes in network architectures

– Performance Energy efficiency driven

– Static Dynamically reconfigurable network

– Dedicated Shared resources

– Separate & complicated Integrated & simplified management layers/interfaces

– Unbalanced Balanced bandwidth link utilization

Traditional Way of Using Wavelengths

TX

TX

TX

TX

RX

RX

RX

RX

SW SW

Optical Network with

Passive/Semi-passive Nodes

New Way of Using Wavelengths

Tunable

TX SW

Tunable

TX SW

Tunable

TX SW

Fixed

RX SW

Fixed

RX SW

Fixed

RX SW

Continuous vs. Burst-Mode Communications

TX RX SW SW ...010110100101110100101001001010101111101001010101…

SONET/SDH

Packet Packet Packet

RX SW 10011…0110

Packet Packet Packet

011…010 011…010

Enabling Technologies

• Common denominator in technologies enabling

flexible, dynamically-reconfigurable optical networks

– New multiple access technologies

• e.g., Hybrid TDM/WDM, OFDMA with POLMUX

– Tunable transmitters (lasers) and receivers (filters)

– Burst-mode communications

• The paradigm shift pushes these technologies

toward the edge of the networks!

Ultimate Optical Network Architecture - 1

• A common network architecture/infrastructure for access/metro/backbone

• To enjoy the benefits of Economy of Scale* by maximizing statistical multiplexing gain over

– Traffic burstiness

– Different usage patterns

• Challenge: How to integrate them all?

Backbone/CoreBackbone/CoreMAN

Access

Access

Residential

Users

Business

Users

Access/MAN/Backbone

Residential

Users

Business

Users

* Factors of 5 to 7 decrease in cost (“Above the clouds”, UC Berkeley)

Ultimate Optical Network Architecture - 2

• Network resource as utility

• Cut the (static) link between fibre infrastructure and pool of network resources (e.g., transceivers)

• Challenge: Everything (both up- and downstream) in burst-mode communications

Fibre Infrastructure

(Access/MAN) …

Transceivers

X

Ultimate Optical Network Architecture - 3

…

…

…

…

… …

…

P-T-P & WDM-PON TDM-PON

Hybrid PON (with advanced architecture)

Ultimate Optical Network Architecture:

Example

SUCCESS-HPON – Hybrid TDM/WDM-PONs

(2003-2005)

Central

OfficeRN

RN

RN

RN

’1, 2

1

2

21

22 23

’1

’3, 4, …1, 2

3, 4, …

3

’3

3

31

32

33

TDM-PON ONU

RN TDM-PON RN

WDM-PON ONU

RN WDM-PON RN

Central

OfficeRN

RN

RN

RN

’1, 2

1

2

21

22 23

’1

’3, 4, …1, 2

3, 4, …

3

’3

3

31

32

33

TDM-PON ONU

RN TDM-PON RN

WDM-PON ONU

RN WDM-PON RN

Protection & restoration is

possible by using different s

on east- and west- bound.

Benefits of Flexible Architecture

R

Tunable

TX 1

Power

Splitter WDM

DEMUX

ONU 1

ONU 16

. .

.

Start small and grow gradually

Benefits of Flexible Architecture

R

R

Tunable

TX 1

Tunable

TX 2

Power

Splitter WDM

DEMUX

ONU 1

ONU 32

. .

.

Start small and grow gradually

Benefits of Flexible Architecture

R

R

Tunable

TX 1

Tunable

TX 2

Power

Splitter WDM

DEMUX

ONU 1

ONU 48

. .

.

R

Tunable

TX 3

Start small and grow gradually

Benefits of Flexible Architecture

R

R

Tunable

TX 1

Tunable

TX 2

Power

Splitter WDM

DEMUX

ONU 1

ONU 64

. .

.

R

Tunable

TX 3

R

Tunable

TX 4

Start small and grow gradually

Benefits of Flexible Architecture

R

R

Tunable

TX 1

Tunable

TX 2

Power

Splitter WDM

DEMUX

ONU 1

ONU 64

. .

.

R

Tunable

TX 3

R

Tunable

TX 4

Flexibility and power efficiency

Usage = 50%

(Compared to Peak) Turn off TX3 & TX4 to save energy

Benefits of Flexible Architecture

R

R

Tunable

TX 1

Tunable

TX 2

Power

Splitter WDM

DEMUX

ONU 1

ONU 64

. .

.

R

Tunable

TX 3

R

Tunable

TX 4

Redundancy and hot-swap capability

TX4 failed The system is still running (with

slightly degraded performance)

TOWARD NEXT-GENERATION

OPTICAL ACCESS

Evolution of Optical Access

OLT

ONU

ONU

ONU

OLT

ONU

ONU

TDM-PON

OLT

ONU

ONU

ONU

ONU

OLT

ONU

ONU

ONU

? LR-PON

WDM-PON

Hybrid PON

Geneva, 19-20 June 2008

Evolution scenario

Now ~2010 ~2015

Power splitter deployed for Giga PON(no replacement / no addition)

Splitter for NGA2(power splitter or something new)

G-PON

GE-PON

WDM option to

enable to overlay multiple G/XGPONs

Co-existence

“Co-existence”arrows mean to allow gradual migration in the same ODN.

NG-PON2E.g. Higher-rate TDM

DWDMElect. CDMOFDM,Etc.

Equipment

be common

as much as

possible

NG-PON1 incl. long-reach optionC

apacity

XG-PON(Up: 2.5G to 10G,

Down: 10G)

Co-existence

Component R&D to enable NG-PON2

A Suggested Time Line from ITU-T/IEEE*

* J. Kani and R. Davey , “Requirements for Next Generation PON,”

Joint ITU-T/IEEE Workshop on NGOA, Jun. 2008.

Areas of Improvement

• Reach – Through amplification

• Bandwidth per subscriber – Higher transmission rate in TDM-PON

– Introduction of WDM

• User base – Serving both residential and business users

through common infrastructure • Stronger protection capability for business users

Candidates for NGOA

• LR-PON

– 10 Gb/s over 100km with up to 1000:1 split ratios*

• WDM-PON

– Use of array of transceivers

– Lack of BW sharing

– Inventory management of ONUs with different s

– Need of colorless or sourceless ONUs

• Hybrid TDM/WDM-PON

– Use of fast tuneable lasers (and receivers)

– Flexible architecture, but complex MAC/scheduling

– How-swapping capability of tuneable components

* MIT CIPS Optical Broadband Working Group

Challenges

• Power Efficiency

– Number of high-powered transceivers and optical amplifiers in use

• Maintenance

– For active components and thermal optical devices in the field

• Backward compatibility

– For current-generation TDM-PONs

• Scalability

– Start small and grow gradually

• Integration with other services

– Wireless/Video overlay

37

BT’s Current

UK Network

BT-21CN

Simplified UK

Network

Current Status of Network

ECR-BASED QUANTITATIVE

ANALYSIS FRAMEWORK

Requirements for 10-Gb/s Optical Access

• ―10 Gbit/s everywhere‖ is taken to mean that any customer premises can

cost-effectively access useful end-to-end symmetrical throughputs of

10Gb/s data on demand (i.e., whenever they want it but it need not

necessarily always be there).‖ [Excerpt from TSB project requirements]

– Major focus on residential and SME customers.

– 10 Gb/s line rate in the access is a necessary but not sufficient condition.

– Some degree of contention assumed at various points in the network

• What is missing here?

– Description/definition which is

• Specific (e.g., What is ―useful‖?)

• Practical & implementable (e.g., any shared architecture can achieve this?)

• Measurable (during the operation in the field)

What Does “10 Gb/s” Means?

• We need a quantifiable and

measurable definition of ―10 Gb/s‖

at the user side for

– Comparative study of candidate

architectures

– Actual implementations

• Our proposal is based on the

extension of the equivalent circuit

rate (ECR)*.

– For general services & applications

in addition to web-browsing and

interactive data

– Taking into account access/metro

part only * N.K. Shankaranarayanan, Z. Jiang, and P. Mishra,

“User-perceived performance of web-browsing and

interactive data in HFC cable access networks,” Proc. Of

ICC, pp. 1264-1268, Jun. 2001.

Server

User

User

Candidate architecture

Server User

User

Y

Z = α*min(X, Y) (α < 1)

The same

perceived

performance

X

Implications on Metro/Access* Architectures - 1

• If we mean by ―10 Gb/s‖ the (extended) ECR of

the network architecture (i.e., Z), we can derive

the following conclusions:

– Point-to-point (including static WDM-PONs)

architectures with a UNI (i.e., Y) of 10 Gb/s can meet

the requirement.

• As far as the NNI (i.e., X) is not a bottleneck.

• But there is no statistical multiplexing gain (i.e., sharing of

resources) in this architecture.

* Not end-to-end.

Implications on Metro/Access Architectures - 2

– Shared architectures with a UNI of 10 Gb/s may not meet this

requirement (i.e., ECR < 10 Gb/s), irrespective of NNI.

• Need to increase either line rate (for TDM-PON & hybrid

TDM/WDM-PON) or number of WDM channels (for hybrid

TDM/WDM-PON) at the UNI.

• Note that the ECR is a function of the architecture, the number

of users, and the nature of services/applications.

ECR-Based Quantitative Analysis Framework –

Rationale

• To take into account the interactive nature of actual traffic (e.g.,

TCP flow control) and the performances perceived by end-users

(e.g., delay in web browsing) in quantification of the statistical

multiplexing gain.

• To capture the interaction of many traffic flows through TCP and a

candidate network architecture.

– Simulation models based on OMNeT++ and INET Framework have

been implemented, which provide models for applications as well as

a complete TCP/IP protocol stack.

Calculating ECR

•DW,R: Web page delay from reference architecture

•DW,C: Web page delay from candidate architecture

Start

i=0

R=R’=Ri

Two-sample hypothesis testing with

•H0: E[DW,R] = E[DW,C]

•H1: E[DW,R] < E[DW,C]

Reject

H0?

Yes

i=i+1

R’=R

R=Ri

Two-sample hypothesis-testing with

•H0: E[DW,R] = E[DW,C] •H1: E[DW,R] E[DW,C]

No

Reject

H0?

ECR=

(R + R’)/2

Yes

ECR=R

No

End

SYSTEM MODELLING

Overview of Hybrid TDM/WDM-PON

Simulation Setup: System Parameters

• N: Number of ONUs (subscribers)

• n: Number of hosts (users) per ONU

• RD: Rate of distribution fibre

• RF: Rate of feeder fibre

• RB: Rate of backbone network (>> N × RD)

• RTT: End-to-end round trip time

System Model - ECR Reference

• N = 16

• n = 1, 2, …

• RU = RD = RF = 10 Gbit/s

• RB = 1 Tbit/s (future standard or MUX of 100 Gbit/s links)

• RTT = 10 ms (including 600 µs RTT in 60-km PON)

App.

Server

ONU

1

ONU

N

…

RD=RF

Host 1

Host n

…

Host 1

Host n

…

RTT

RB OLT

RU

System Model – Hybrid PON

• N = 16

• n = 1, 2, …

• RU = RD = RF = 10 Gbit/s

• TX = RX = 1, 2, …

• RB = 1 Tbit/s

• RTT = 10 ms

RF App.

Server

ONU

1

ONU

N

…

RD

RD

Host 1

Host n

…

Host 1

Host n

…

RTT

RB OLT

RU

TX, RX

TRAFFIC MODELLING

Hierarchical Model Construction

Application

Host (e.g., PC)

ONU (w/ Ethernet Switch)

Service

User

Subscriber (Household)

Overview of Host (User) Node - 1

HTTP 1

TCP

UDP

Network

and

Lower

Layers

HTTP nh

…

FTP 1

FTP nf

…

Video 1

Video nv

…

UNI

Overview of Host (User) Node - 2

• nh = nv = 1

– Assume that a user can watch only one video channel and

interact with only one web session simultaneously at any given

time.

• As far as user perceived (interactive) performance is concerned.

• nf should be kept large to load the high-speed access link.

– FTP is usually background process.

• This could be HTTP sessions just downloading files.

– Suggest 10 as a starting point.

Observations & Comments

• For study of network architectures/protocols, the

frame/packet-level traffic modelling is not very useful.

– e.g., Packet inter-arrival statistics highly depend on network

architectures/protocols.

• We will focus on application level traffic modelling, i.e.,

above transport layer (TCP/UDP).

– Statistics on sources (e.g., file size for FTP and frame size for

video) and user behaviour are critical.

– It is, however, extremely difficult to find such data!

HTTP Traffic Model - 1

• A behavioural model for user(s) web browsing based on [2] with following

simplification:

– No caching and pipelining

– Adapted for traffic generation at the client side

Server

Client

Request for

HTTP object

Request

for embedded

object 1

Response

Parsing Time Reading Time

…

Request

for embedded

object 2

Response to the last

embedded object Request

for HTTP

object

Web page delay (= session delay*)

* Include connection (i.e., socket) set-up time as well (which is not shown in the figure).

HTTP Traffic Model -2

Parameters / Measurements Best Fit (Parameters)

HTML Object Size [Byte] /

Mean=11872, SD=38036, Max=2 M

Truncated lognormal (=7.90272,

=1.7643, max=2 M)

Mean=12538.25, SD=45232.98

Embedded Object Size [Byte] /

Mean =12460, SD=116050, Max=6 M

Truncated lognormal (=7.51384,

=2.17454, max=6 M)

Mean=18364.43, SD=105251.3

Number of Embedded Objects /

Mean=5.07, Max=300

Gamma (=0.141385, =40.3257)

Mean=5.70, SD=15.16

Parsing Time [sec] /

Mean=3.12, SD=14.21, Max=300

Truncated lognormal (=-1.24892,

=2.08427, max=300)

Mean=2.252969, SD=9.68527

Reading Time [sec] /

Mean=39.70, SD=324.92, Max=10000

Lognormal (=-0.495204, =2.7731)

Mean=28.50, SD=1332.285

Request Size [Byte] /

Mean=318.59, SD=179.46

Uniform (a=0, b=700)

Mean=350, SD=202.07

Streaming Video Traffic Model - 1

• HDTV quality, realistic, high bit-rate video traffic models are

needed for NGOA

– Use H.264/AVC video traces

– ―Terminator 2‖ VBR clip from ASU Video Trace Library

• Duration: ~10 min

• Encoder: H.264 FRExt

• Frame Size: HD 1280x720p

• GoP Size: 12

• No. B Frames: 2

• Quantizer: 10

• Mean frame bit rate: 28.6 Mbit/s

» ~334 streams needed to fill 10 Gbit/s line with the following assumption.

Streaming Video Traffic Model - 2

• Interface with OMNeT++/INET framework

– Through ―UDPVideoStream{Svr,Cli}WithTrace‖ modules:

• UDP server can handle multiple client requests simultaneously

• Random starting phase for each request

• Wrap around to generate infinite streams

• UDP client records the following performance metrics:

» Packet end-to-end delay (vector)

» Packet loss rate

» Frame loss rate

» Decodable frame rate (perceived quality metric)

FTP Traffic Model - 1

• A simple model for user(s) file downloading based on [3]:

– The model is for a data transfer connection only.

– Multiplexed (nf = 10) to emulate future FTP/data services at 10 Gbit/s rate

– Adapted for traffic generation at the client side

Server

Client

Request for

a file to download

Reading Time

Response to the last

embedded object

Request for

a file to download

File download delay

(= session delay)

FTP Traffic Model -2

Parameters Probability Distribution Function

(PDF)

File Size [Byte] /

Mean=2 M, SD=0.722 M, Max=5 M

Truncated lognormal (=14.45,

=0.35, max=5 M)

Mean=1995616(~2 M),

SD=700089.8(~ 0.70M)

Reading Time [sec] /

Mean=180

Exponential (=0.006)

Mean=166.667, SD=166.667

Request Size [Byte] /

Mean=318.59, SD=179.46

Uniform (a=0, b=700)

Mean=350, SD=202.07

Simulation Environment

OMNeT++ with

INET framework

Streamline Linux Cluster

• 22 computing nodes (each with 8 cores and 8GB memory)

• Total 176 cores and 176 GB memory

INITIAL RESULTS &

DISCUSSIONS

ECR Reference – Web Page Delay

Hybrid TDM/WDM-PON – Web Page Delay

Hybrid TDM/WDM-PON – ECR

Hybrid TDM/WDM-PON –

Min. Number of TXs to Achieve ECR of Rtarget

Discussions - 1

• Dedicated architectures with 10-Gb/s line rate — including

static WDM-PON — can provide 10-Gb/s ECR (by

definition).

– As far as there is no contention in the network side.

– But, we cannot enjoy any statistical multiplexing gain

(i.e., sharing of resources) other than some fibre

infrastructure in case of WDM-PON.

Discussions - 2

• Hybrid TDM/WDM-PON with 10-Gb/s line rate can also provide

10-Gb/s ECR with multiple transceivers whose number

depends on traffic load.

– It is remarkable that hybrid PON with just one transceiver

can achieve 10-Gb/s ECR until n reaches 5.

• When n=5, streaming video traffic alone pushes about

150-Mb/s stream into ONU and 2.4-Gb/s multiplexed

stream into OLT (out of 16 ONUs).

– An ideal shared architecture would be that of large split

ratio with multiple wavelength channels.

• i.e., SuperPON + hybrid TDM/WDM-PON

Summary

• Changing business environment and demands are driving forces behind the paradigm shift in optical networking toward

– Flexible, dynamically-reconfigurable network to better utilize network resources

– Passive/semi-passive network to maximise energy efficiency

– A common network infrastructure for access/metro/backbone

• We have been working on the following tasks to realize 10-Gb/s NGOA solutions:

– Investigate candidate architectures in terms of cost, power efficiency, maintenance, scalability, and extensibility.

– Propose ECR-based comparative analysis framework and demonstrate benefits of shared architecture (e.g., hybrid PON) based on it.

References

1. N.K. Shankaranarayanan, Z. Jiang, and P. Mishra, ―User-

perceived performance of web-browsing and interactive

data in HFC cable access networks,‖ Proc. Of ICC, pp.

1264-1268, Jun. 2001.

2. J. J. Lee and M. Gupta, ―A new traffic model for current

user web browsing behavior,‖ Research@Intel, 2007

[Available online].

3. cdma2000 Evaluation Methodology, 3GPP2 C.R1002-B,

3GPP2 Std., Rev. B, Dec. 2009 [Available online].

70

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presentation, please visit

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