Ioannis Tomkos
Ioannis Tomkos “
“High Speed Networks and Optical Communications High Speed Networks and Optical Communications -- NOCNOC”” Research Group
Research Group
Converged optical network
Converged optical network
architectures
Outline
Outline
Highly-demanding bandwidth-hungry and QoS-sensitive new services are demanding new networking solutions and network design paradigms
• What solution is in our hands currently?
Network design: past & future
• Where things are heading to?
Optical network architecture evolution
• What are the different areas where convergence might be required?
Relevant research activities and results on topics related with convergence (AIT’s activities)
• TRIUMPH, DICONET and ACCORDANCE EU research projects
Optical technology
Optical technology
-
-
past
past
Optics up to 2000:
• Transmission plant capable of Tb/s transmission
• Hundreds of λs
• Hundred to thousands of km transmission in-between regenerators
2000 – today
• Reconfigurable all-optical networks →Advanced devices:
– Reconfigurable Optical Add/Drop Multiplexers (ROADMs) – Wavelength Selective Switches (WSSs)
• Longer capacity x reach product at high spectral efficiencies
→Novel modulation formats and transponder concepts
– DPSK, DQPSK – Coherent systems
• Optical technology finally reaches the access part
→Point-to-Point Ethernet
→Passive Optical Networks (PONs) What’s next?
Future capacity demands
Future capacity demands
New types of services emerging in Access
• High speed access via FTTx, DSL or wireless
→ reach content web pages (e.g. flash enabled)
→ large volume emails (e.g. gmail)
• Voice over IP applications (e.g. Skype) • Video distribution services (e.g. YouTube) • Interactive multi-player gamming
• Video on demand (e.g. Triple-play services)
Problems
• How to further optimize the network operation and reduce energy requirements? • How to upgrade networks in order to meet future demands?
• How to achieve compatibility with existing solutions in order to:
→ Ease control
Need for high capacity
connections Access Æ Metro
Even larger volumes of data carried in core networks
Network design
Network design
-
-
past
past
In order to make our work easier, we split the network in different pieces:
• layers (physical, network, service, etc.) • segments (access, metro, core)
• switching technologies (packets, circuits, etc.) • administrative domains (multi-domain networks) • technology domains (optical, wireless)
Such divisions enabled optimized designs within each different piece of the network. However, in some cases the level of abstraction taken as a fact for the other pieces of the network by network designers was oversimplified and far from being realistic!
In some cases there was no consideration what so ever on the issues that arise when you try to put together the different pieces of the network and what you have to pay in return for such suboptimal approach
• Lack of network efficiency (e.g. under-utilization of resources, stranded bandwidth, reduced QoS) • Large power consumption
• Significant OPEX
Network design
Network design
-
-
future
future
Removing the segmentations among the different pieces of the network
• Cross-layer optimization (physical/network, network/service, etc.) • Multi-granularity switching nodes (OCS/OFS/OBS/OPS)
• Introducing end-to-end network solutions by removing the boarders among access, metro and core network segments
• Introducing end-to-end network solutions by allowing more flexible and efficient interconnection among different administrative network domains
• Introducing end-to-end networks solutions across technology domains (optical/wireless)
Develop Converged Network Infrastructure ensuring further optimization and benefits for the users and services
• Lower CAPEX/OPEX • Low power consumption • Better QoS/QoE
• Support for new services
Future network architecture
Evolution in Optical Network Architectures
Evolution in Optical Network Architectures
Network architectures can be differentiated in terms of
• o-e-o regenerators used• administrative domains interworking • switching scheme used
• network layers
• network segments used
• technology domains coexistent
The aforementioned categories denote also the possible areas of
convergence
• Some overlap among the different categories exist…
Can we find a solution that can be the “convergence enabler”
across all different categories?
Network architectures in terms of o-e-o
regenerators used
Opaque
(o-e-o everywhere)
Transparent
(o-e-o nowhere)
Future high capacity networks require an
Future high capacity networks require an efficientefficient, , flexibleflexible and and
Infinera others
R. Wagner, LEOS 2000, TuC1, November 2000
?
Network architecture approaches in terms of
Network architecture approaches in terms of
regeneration needed
Limitations of transparent optical networks
Limitations of transparent optical networks
In transparent networks signal
In transparent networks signal impairments accumulateimpairments accumulate ::
•
• DispersionDispersion
•
• ASE noiseASE noise
•
• Fiber nonlinearities Fiber nonlinearities
•
• CrosstalkCrosstalk
•
• PMDPMD
In dynamically reconfigurable networks the window of operability
In dynamically reconfigurable networks the window of operability is significantly is significantly reduced:
reduced:
¾ The temporal variability of the transmission parameters prohibits efficient static pre-compensation of the impairments
Failures propagate
Failures propagate in a transparent network environment and therefore they canin a transparent network environment and therefore they can’’t be t be easily localized and isolated
easily localized and isolated
Appropriate pre-planning may improve the window of operability
Overcoming the problems
Overcoming the problems
Use of optoelectronic regenerators on per channel basis
• enabling impairment compensation and BER monitoring
Use of dynamic impairment management techniques that may be
implemented in-line (e.g. optical means of impairment compensation) or at the optical transponder interfaces (e.g. electronic mitigation of
impairments)
• Some techniques require performance/impairment monitoring (optical or electrical) for offering dynamic operation
In addition to physical layer impairment management techniques, the
network designer may use certain Routing and Wavelength Assignment
(RWA) algorithms that take into account the signal impairments (IA-RWA) and constrain the routing of wavelength channels according to the
physical characteristics of the optical network paths.
• Such capability can be used as a tool for improved efficient network design and planning of advanced mesh optical networks
Transparent Optical Networks
Transparent Optical Networks
The introduction of more optical transparency in the network
promises a series of advancements in the way the network
operates and the benefits expected by end-users and services
However realizing an end-to-end transparent optical network is
very challenging and requires several
new technology
innovations
(once realized though, it should be very easy to
manage)
• Novel modulation formats (OFDM?) and amplification schemes • All-optical (multi-wavelength!) regeneration
• All-optical sub-wavelength traffic switching/grooming • New algorithms and control plane extensions
Alternatively a translucent (managed-reach) semi-transparent
network may be an alternative option, which however requires
a lot of complexity in managing the infrastructure
Network architectures in terms of administrative
domains interworking
Single domain
(isolated due to different operators, …)
Multiple domains
(interworking)
Multi
Multi
-
-
domain networking
domain networking
Multi-domain aspects in transparent/translucent networks have
not been considered in detail so far
• Current developments have been mostly conceived for single-area networks
While there will be a must in the near future, the
protocols/techniques for achieving truly end-to-end optical
connections (spanning different domains) have not yet been
devised.
Efforts are being initiated or are underway on the development of
new features enhancing the GMPLS control plane performance.
• An integrated GMPLS based multi-layer and multi-domain control plane, which allows a more efficient use of the network resources, is a key
Control plane elements to address multi
Multi
Multi
-
-
domain issues
domain issues
To achieve end-to-end lightpaths establishment in multi-domain networks, several domains should cooperate at the data, control and management plane levels and following a well defined yet diverse number of interconnection and information exchange models.
Some key issues with respect to inter-domain networking are:
• How to exchange networking information between domains for routing purposes. • How to negotiate QoS parameters between domains taking into account the
heterogeneous mix of services and the particular policies applied. • How to ensure coordinated resilient operation.
• How to provide interfacing between different technologies.
• How to interface control planes, which are usually running on a single domain
The different interconnection models, defined at specific reference points such as the User-Network Interface (NNI) or the External and Internal Network-Network Interfaces (E-NNI and I-NNI), are characterized by the type and amount of
information that is exchanged at network domain edges, by the applicable control procedures and by the service selection and activation methods.
Network architectures in terms of switching
scheme used
Convergence of switching techniques
Convergence of switching techniques
The network evolution mandates a framework that can provide
control and management of traffic (dynamic bandwidth
allocation) in multiple levels of granularity (fibre / waveband /
wavelength / burst / packet / timeslot)
A convergence of the various existing optical switching
techniques (optical circuit/flow/burst/packet switching) is
mandatory in order to achieve optimal exploitation of the
network resources.
• Hybrid switch implementation (combining all switching schemes) • A switching scheme that can adapt to any traffic
characteristics/requirements (Polymorphous OBS?, OFS?) • Observation: All techniques that achieve fine sub-wavelength
granularity utilize the time dimension to allocate bandwidth to different users/services. Can the frequency domain being used instead?
Optical circuit switching for core networks
Optical circuit switching for core networks
In the backbone networks, clearly optical circuit switching is so
far the winner
• Can it continue to be in the future? How it should adapt?
Wavelength routed all-optical switched networks is the current
state of the art under the optical circuit switching paradigm
• Now: Lightpaths
• Future: Lightrails, lightrees, etc.
However Optical Time Division Multiplexed networks might be a
future solution
• Enabler for 1TbE?
TDMA based access networks
TDMA based access networks
In the access part of the network TDMA based
protocols are dominating
• E-PON
• G-PON
→ Can they continue to scale beyond 10G symmetric?
WDM-PON is trying to make a paradigm shift from
time-domain to frequency (wavelength) domain
OFDMA-PON proposed by NEC is also using the
Network architectures in terms of network layers
Single layer optimization
(physical, network, service)
Cross layer optimization
Network layers convergence
Network layers convergence
In order to handle the huge available capacity in the most efficient and dynamic way a convergence between multiple layers in the protocol stack - namely physical, network, transport and application - is imperative.
This involves designing the optical network with the main concern being the quality of the services that will be carried over it and includes
optimization of protocols belonging to multiple levels of the stack for their best possible interoperability
• e.g. providing services requirements to the network design (service oriented optical networking)
• e.g. adjusting TCP functionality or parameters to enhance the operation of the underlying switching schemes
• e.g. designing the optical switching protocols in a way that respects specific service performance requirements and reconciling concepts such as IP over optical networks
• e.g. optimizing the network design by considering the physical layer
capabilities of the network (impairment-aware optical networking – more details follow in the next slides)
Impairment Aware Optical Networking
Impairment Aware Optical Networking
Receive performance monitoring information related with
impairments in the network or/and calculate the impact of
impairments
+
Run routing and wavelength assignment algorithms that take
impairment information into consideration (IA-RWA)
IA
IA
-
-
RWA in transparent networks
RWA in transparent networks
IA
IA
-
-
RWA can be used either for pre
RWA can be used either for pre
-
-
planning purposes (simple) or
planning purposes (simple) or
for dynamic network optimization (demanding)
for dynamic network optimization (demanding)
An operator who wants to avoid having to provide impairment
An operator who wants to avoid having to provide impairment
-
-related parameters to the control plane may elect to treat them
related parameters to the control plane may elect to treat them
at the
at the
system design and
system design and
static pre
static pre
-
-
planning
planning
level.
level.
•
• In this approach the operator can preIn this approach the operator can pre--qualify all or a set of feasible endqualify all or a set of feasible end--toto--end end optical paths
optical paths
In
In
dynamic network optimization
dynamic network optimization
the calculations or/and
the calculations or/and
measurements should be performed on real time and make use of
measurements should be performed on real time and make use of
the current state information aiming to minimize the blocking
the current state information aiming to minimize the blocking
probability of new connection requests while guaranteeing the
probability of new connection requests while guaranteeing the
performance of the established connections
Challenges for the development of cross
Challenges for the development of cross--layer layer optimized network operation/planning
optimized network operation/planning
How to collect the impairment information from the network?
How to collect the impairment information from the network?
•
• Requires the development of optical monitorsRequires the development of optical monitors
How to model fast and accurately the physical layer
How to model fast and accurately the physical layer
impairments
impairments
•• Speed is required in the onSpeed is required in the on--line caseline case •
• Accuracy is required in the offAccuracy is required in the off--line case line case
What is the optimal route?
What is the optimal route?
•
• Requires development of appropriate algorithms able to calculateRequires development of appropriate algorithms able to calculate fast fast and accurately the optimal route
and accurately the optimal route
How to inform the network?
How to inform the network?
• Requires the investigation of control protocol extentions (based on extending current protocols options, like GMPLS OSPF or/and RSVP)
The DICONET consortium
The DICONET consortium
DICONET
DICONET
–
–
Dynamic Impairment
Dynamic Impairment
Constraint Optical Networking
Constraint Optical Networking
DICONET project scope and solution framework
DICONET project scope and solution framework
DICONET scope
• The development of a dynamic network planning/operation tool
residing in the core network nodes that incorporates real-time
measurements/calculations of optical layer performance into IA-RWA algorithms and is integrated into an IA- control plane
DICONET key elements
• Physical layer monitoring • Physical layer modeling • Physical layer aware RWA • Physical layer aware GMPLS
Monitoring: OIM & OPM Techniques
Monitoring: OIM & OPM Techniques
WDM Layer Parameters Signal Quality Parameters Aggregate power Channel Power Channel wavelength Spectral OSNR In-band OSNR Q-Factor/BER Bit Rate Jitter Digital techniques
Digital techniques use highuse high--speed logic to process digital information encoded on the opticaspeed logic to process digital information encoded on the optical l waveform
waveform
¾
¾ Cannot isolate the effects of individual impairmentsCannot isolate the effects of individual impairments
¾
¾ BER computation is not fastBER computation is not fast(complex, expensive)(complex, expensive)
Analog techniques
Analog techniques treat the optical signal as an analog waveform and measure its streat the optical signal as an analog waveform and measure its specific pecific
characteristics characteristics Time domain : Time domain : Eye diagrams Histograms
Auto/cross correlation meas.
Frequency domain :
Frequency domain :
Optical Spectrum
RF amplitude Spectrum
• D. Kilper et. al., “Optical Performance Monitoring”, JLT 2004
• C. Mas, I. Tomkos “Failure management in optical networks”, (invited) ICTON, 2003
-300 -200 -100 0 100 200 300 -12 -11 -10 -9 -8 -7 -6 -5 -4 LOG (B ER) Threshold Voltage (mV)
Signal Performance Modelling based on Q
Signal Performance Modelling based on Q--Factor (QFactor (Q--tool)tool)
π 2 2 2 1 2 2 Q e Q erfc BER Q − ≈ ⎟ ⎠ ⎞ ⎜ ⎝ ⎛ = Probability Threshold voltage Vth V (1) σ(1) σ(0) V (0)
Random amplitude perturbations are considered with Gaussian dist
Random amplitude perturbations are considered with Gaussian distributionsributions
1 0 1 0 1, 0,
1, 0, 1 0 1, 0,
( ) ( )
start start
end end end end
end start
end end start start end end
start I I I I Q Q I I Eyeimpairments Noiseimpairments Q
σ
σ
σ
σ
σ
σ
⎛ ⎞ ⎛ − ⎞ − ⎛ + ⎞ =⎜⎜ ⎟⎟ =⎜⎜ ⎟⎟×⎜⎜ ⎟⎟× + − + ⎝ ⎠ ⎝ ⎠ ⎝ ⎠ = × ×Reference Network
Reference Network
National topology based on the
Deutsche Telecom (DT-net) Network
Parameter Value Number of Nodes 14 Number of links 23
Node degree 3.29 (min: 2, max: 6)
Link Length (km)
186 km (min: 37, max: 353)
Off
Off--line planning performance results line planning performance results –– Real TrafficReal Traffic
DTnet - Real traffic load
Formulation running time (sec) RWA 476 RWA-p 10750 Sigma Bound 4610
Running times for W=50
IA-RWA 2 manages to pass all connections with W=50 and also have acceptable running time
Online network planning issues
Online network planning issues
Once connections are established and the network is operational,
how to decide how to handle a new connection request?
The new lightpath that will be established, will affect the other
already established lightpaths
• Thus, when a lightpath is established the quality of transmission of some already established lightpaths may become unacceptable
→These connections have to be rerouted!
Rerouting a connection is a process that we want to avoid
• it involves tearing down the previous lightpath, re-executing the algorithm and establishing a new lightpath
• all these actions would interrupt the service of the connection and possible affect the quality of service exhibited by the end users
On
On
-
-
line planning performance results
line planning performance results
DT network
Poisson arrivals (λ=1) ,
exponential duration
(1/μ=100)
Three algorithms developed
and evaluated according to:
• Blocking probability • Average number of
“reroutings” per request • Acceptable execution times
(~msec per request)
0.00 0.01 0.02 0.03 0.04 0.05 0.06 0.07 15 20 25 30 35 available wavelengths B lo c k ing pr ob abi li ty MUW bQ-MUW bQ 0.00 0.01 0.10 1.00 15 20 25 30 available wavelengths R e ro u tin g p ro b a b ilit y MUW bQ-MUW bQ
MUW: Most Used Wavelength
bQ: Better Q Performance
Towards IA Control Plane
Towards IA Control Plane
There are generally three approaches to incorporate
physical layer impairments information in the control
plane:
• Routing protocol based
• Signaling protocol based
• PCE based
What are the changes that need to be made in order to
turn those approaches to an Impairment Aware
Control Plane?
IA Control Plane
IA Control Plane
-
-
Signaling approach
Signaling approach
IA Control Plane
IA Control Plane
-
-
Routing approach
Routing approach
PCE (Path Computation Element) approach
PCE (Path Computation Element) approach
Network architectures in terms of network segments
Multiple segments
(Access, Metro, Core)
Network Segments and characteristics
Network Segments and characteristics
Long Haul: National or regional inter-city longer span
Access: Residential access (CO or Head-end to residential subscriber) • Distances: 100’s to 1000’s of km
• Rates: from 2.5 Gb/s to 40 Gb/s
• 40 to 80 DWDM Channels
• Distances: 10’s to 100’s of km (up to 400) • Rates: from 633 Mb/s to 2.5 Gb/s
• ATM / Sonet, GbE, up to 40 DWDM Ch.
• Distances: 10’s or less
• Rates: from OC-3 (155) to OC-12 (633) • Sonet & ATM, GbE, CWDM ?
POP
POP
POP
POP
Access Feeder
Access Feeder
Regional: City to city (little grooming)
Metro: Office-to-office, switch-to-switch traffic within city (grooming)
Network segmentation trends
Network segmentation trends
Currently the different network segments (access, metro, core) have different traffic characteristics to serve, different cost points to satisfy, different bit-rates and transparent reach to handle
• However, it appears that the metro segment most likely will vanish in the near future
Core networks will be connected directly to extended reach access networks, thus minimizing the number of central offices and cabinets/base-stations that the
operators have to manage (resulting in less power consumption and OPEX costs)
Present optical access systems mainly use PtP and PON technologies with a trend to extend reach and split which enables reduction of POPs in the access area.
Thus, future access nodes will be required to handle multiple Gbps of traffic, making the concept of a converged (even from a topological point of view) access/metro/core network seem logical, if not unavoidable.
But what will be needed to transparently
But what will be needed to transparently
cross network segments?
How grooming works
How grooming works
www.ait.gr
www.ait.gr
Lessons learned from SDH/SONET
Lessons learned from SDH/SONET
• Grooming requires a mix of
space switching (port-to-port) and time domain switching (time slot to time slot).
• This allows for the most
efficient utilization of network bandwidth.
• The optical switching
systems need to employ
grooming capabilities to ease market entry.
The TRIUMPH consortium
The TRIUMPH consortium
TRIUMPH
TRIUMPH
–
–
Transparent ring
Transparent ring
interconnection using multi
interconnection using multi
-
-
wavelength
wavelength
photonic switches
Interconnection between rings requires edge node (TRIUMPH)
• 2R multi-wavelength regeneration
• Transparent traffic grooming with time slot interchange
TRIUMPH Project Concept
TRIUMPH Project Concept
High capacity network with trans-parent connection between metro / core rings (130 Gbit/s per λ-channel) and metro / access rings (43 Gbit/s per λ-channel)
Experimental Results
Experimental Results
More Switching Scenarios
More Switching Scenarios
Time slot interchange
Network architectures in terms of technology
domains coexistent
Wireline
Wireline
-
-
wireless convergence
wireless convergence
The access part of the network has traditionally been the
bottleneck of the whole system.
• DSL technology is reaching its limits
• Wireless access becomes more and more pervasive
• Fibre to the Home (FTTH) solutions are becoming more and more prominent
Hence, considerable enhancements in the access part of the
network are needed and include the convergence of wireline
optical and wireless technology reaching a hybrid
optical/copper/wireless access infrastructure that will facilitate
user mobility and support the vast number of devices and sensors
that will need to connect to the internet from the user premises
The ACCORDANCE consortium
The ACCORDANCE consortium
ACCORDANCE
ACCORDANCE
–
–
A Converged Copper
A Converged Copper
-
-
Optical
Optical
-
-
Radio
Radio
OFDMA
OFDMA
-
-
based Access Network with high Capacity and
based Access Network with high Capacity and
flExibility
ACCORDANCE research initiative
ACCORDANCE research initiative
ACCORDANCE (A Converged Copper-Optical-Radio OFDMA-based Access Network with high Capacity and flExibility) introduces a novel ultra high
capacity (even reaching the 100Gbpsregime) extended reach optical access network architecture based on OFDMA (Orthogonal Frequency Division
Multiple Access) technology/protocols (based on concepts introduced by NEC), implemented through the proper mix of state-of-the-art photonics and
electronics.
• Such architecture is not only intended to offer improved performance compared to evolving TDMA-PON solutions but also inherently provide the opportunity for convergence between optical, radio and copper-based access (common PHY).
ACCORDANCE hence aims to realize the concept of introducing OFDMA-based technology and protocols (Physical and Medium Access Control layer) to provide a variety of desirable characteristics, such as increased aggregate
bandwidth and scalability, enhanced resource allocation flexibility, longer reach, lower equipment cost/complexity and lower power consumption, while also
State of the Art on OFDM technology
State of the Art on OFDM technology
OFDM: Modulation method for better transmission properties of bit streams
• Utilizes several low bit rate sub-carriers of the link to carry different QAM symbols simultaneously
OFDMA: Application of OFDM as a scheme allowing for multiple access
• i.e. different users assigned to different sub-carriers
OFDM technology currently used in:
• Copper, in the xDSL links using DMT (Discrete Multi-Tone) modulation format • Radio (WiFi:802.11a, 802.11g, WiMax:802.16e-2005, 3GPP LTE)
• Indoor Power Line Communications (PLC), with the HomePlugAV specifications
Recently OFDM(A) makes its way into the optics world
• A few recent studies show that OFDM can provide high capacity, long-reach and cost-effective operation for Passive Optical Networks (OFDMA-PONs by NEC)
Convergence of optical infrastructure with wireless solutions also employing OFDM technology seems a beneficial direction to go
Concepts of ACCORDANCE research initiative (1/2)
Concepts of ACCORDANCE research initiative (1/2)
Concepts of ACCORDANCE research initiative (2/2)
Concepts of ACCORDANCE research initiative (2/2)
Example of (a) downstream FDM window assignment under an “Optical
ACCORDANCE Benefits
ACCORDANCE Benefits
Improvement of transmission properties
Dynamic Bandwidth Allocation
Virtualization of Resources
Cost-effectiveness
Novel business and tariff models
Smooth migration from current technologies
Summary
Summary
Next generation networks are facing new challenges and they needNext generation networks are facing new challenges and they need to transform to transform
We discussed the future network design principles with a particular view on optical network architecture evolution
The optical network architectures were categorized in terms of
• o-e-o regenerators used
• administrative domains interworking • switching scheme used
• network layers
• network segments used
• technology domains coexistent
In each category, the different areas where convergence might be introduced to benefit the future traffic characteristics/requirements were analyzed
• New research directions were highlighted
Relevant research activities and results on topics related with convergence where presented
Thank you!
Thank you!
Acknowledgements for contributions in this presentation:
Acknowledgements for contributions in this presentation:
- All partners of TRIUMPH, DICONET, ACCORDANCE - Dr. D. Klonidis, Dr. Y. Pointurier, Dr. K. Kanonakis
