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Public defence of Ph.D. thesis Network Layer Studies of the Hybrid Optical Migration Capable Network with Service Guarantees Presented on the 6 th of May 2011 Andreas Kimsås. Name, title of the presentation. Agenda. Optical Internet backbone networks OpMiGua Concept Hybrid networks - PowerPoint PPT Presentation
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Public defence of Ph.D. thesis
Network Layer Studies of the Hybrid Optical Migration Capable Network with Service Guarantees
Presented on the 6th of May 2011Andreas Kimsås
Name, title of the presentation
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Agenda
Optical Internet backbone networks OpMiGua Concept Hybrid networks Research papers
Physical layer aspects & switch design Performance evaluation of original concept Reliability aspects Extensions to orignal concept
Conclusions
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OPTICAL NETWORKSBasic concepts & future needs
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MetropolitanSDH RingNetwork
GSMAccess network
Fiber AccessFTTH triple play
ISDNTelephony
Access network
WiMaxAccess network
MetropolitanIP network in
Mesh topology
Core wavelength-routed optical network in physical
mesh topology
ACCESS
METRO
METRO
CORE
Network overview
• Divided into capacity and extent; access, metro & core
• Data, control & management planes
• Distributed control and management. Several protocols and management strategies in use.
• Diverse physical and logical topologies
• Diversity in equipment at physical and medium access level
• A wide range of services to be supported
A non-homogeneous mix
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Service requirements
The OpMiGua network should accomodate high bandwidth as well as differentiated QoS and QoR.
Bandwidth, Reliability & Performance
Delay• Interactive real-time
•Real-time•Transactional
Information loss•Loss sensitive•Loss resilient
QoS
Protection
Restoration
QoR
Low bandwidth
High bandwidth
Bandwidth
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THE OPMIGUA PROJECTTechnical concept & project organization
7The OpMiGua node
Guaranteed Service Type (GST) traffic is wavelenght routed
Statistically multiplexed (SM) traffic is packet switched onto the GST circuits.
Absolute priority to GST traffic.
Requires dectection of traffic class (e.g. polarization), and logic for inserting SM packets. Simplified operation
Combining circuit & packet switching
λ1
λ2
λ3
λ3
λ2
λ1
From OpMiGua Core
From GST ingress To GST egress
To OpMiGua Core
OXCOXC
SM dropSM drop
SM ingress
Control Unit
Delay
Delay
GST detect
OPS
SM addSM add
SM egress
GST packetLegend: SM packet GapGST packetLegend: SM packet Gap
OpMiGua core node
8The OpMiGua network
SM layer: logical = physical topology. SM traffic is routed hop by hop, but may use a GST connection that terminates in a different place.
GST layer: logical != physical topology. No processing required in core nodes. GST traffic is unaffected by SM packets
Physical layer: GST and SM packets share the same wavelength, but are not superimposed in time.
Simplified operation
Physical and logical dataplanes
λ1
λ2
λ3
WRON for GST traffic
λ1
λ1
λ1
OpMiGua: fully shared fibre resources
GST SM
λ1
λ2 λ3
OPS for SM traffic
λ1
λ1 λ2 λ3
λ1SM
Packet switch
OXC
OpMiGua node PolTDM
9OpMiGua project
Partners: NTNU, Telenor & Network Electronics
OpMigua concept presented in 2003 by S. Bjørnstad, the 3 year joint project stared in 2004.
30 conference & journal papers, 7 master thesis and 2 Ph.D thesis
Physical layer (Tuft), Network layer (Kimsås)
- a joint industry/university project
Home page: www.opmigua.com
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HYBRID NETWORKSClassification of
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Hybrid Optical Network
Client-Server
Parallel
Integrated
Hybrid network classification
«An optical network architecture is called hybrid if it combines two or more basic network technologies at the same time»,
Gauger & Breusegem
G-MPLS PATON Light-Frame
HOS SLIP-IN HOTNET OBTN
OpMiGua ORION Hy-Labs
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RESEARCH PAPERSA short overview of the
13Publications
Nine included papers (P1-P9).N6 is not included in the thesis.
5 reasearch areas combining simulation, experiment & analysis. I am the first author in 5 papers.
P4 is the result of COST-291 collaboration with IKR, Stuttgart
a quick overview
Home page: www.opmigua.com
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P1: Bit errors & packet loss
Result: If the network already has moderate PLR the system can use higher than «usual» BER, without affecting the performance.
Also, FEC is much more important in OBS networks than for the OpMiGua network.
a cross-layer study
Ref: A. Kimsås, H. Øverby, S. Bjørnstad, V. L. Tuft: “A Cross Layer Study of Packet Loss in All-Optical Networks”, AICT, 2006
Goal: to show the relation between BER and PLR
Method: i.i.d. and constant BER at each hop.
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P2: AWGshare switch design
Very low PLR from: SNB property Statistical multiplexing
gain buffering
Scalability demands: Fully shared buffers Realistic cascadability Moderate coupling loss Limited tuning range Realistic AWG size
Functionally equivalent to 3-stage Clos
Ref: A. Kimsås, S. Bjørnstad, N. Stol, D.R. Hjelme: “AWGshare - a Highly Scalable Optical Node Design with Fully Shared Buffers”,
Optical Network Design and Modelling, 2011
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P2: Switch design
Number of AWG routers is function of F, not W Tuning range is function of W, not FW W buffer interfaces are saved compared to Clos & Ngo
- Comparison with known designs
Ref: A. Kimsås, S. Bjørnstad, N. Stol, D.R. Hjelme: “AWGshare - a Highly Scalable Optical Node Design with Fully Shared Buffers”,
Optical Network Design and Modelling, 2011
DesignTWC FWC AWG router Mux/Dmux Couplers
Number Max. Range Number Number Max. Size Number Number Max. Loss
AWGshare 4FW 2W 0 F+1 2W 3F 2W+F 1:W
Clos – AWG based 5FW 2W 0 F+2W-1 2W 3F F 1:2W
Ngo 5FW-2Fb Max[2W/b,Fb] 0 Fb +2W/b-1 Max[W/b,Fb] F F 1:2W
Cheyns Multiport FW FW FW 1 W 2F+W W 1:F
Classic single-stage AWG FW FW FW 1 FW 2F - -
KEOPS - B&S - - 2FW - - 2F+ FW+1 1 1:FW
17P3: Packet loss in an OpMigua node
It is crucial to account for reservation induced blocking (RIB).
Closed form expression was found, acting as a lower bound to packet loss.
Approximation proved to give good agreement with simulations. GST load is increased as function of FDL delay D.
Markov model (Engseth)
A. Kimsås, H. Øverby and N. Stol: “Analysis of a Bufferless OpMiGua Node”, in AICT, 2009
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The PLR decreases as function of GST aggregation at ingress.A closed form expression was developed, excellent results for B > 100.
P3: Analysis of an OpMigua node Results
A. Kimsås, H. Øverby and N. Stol: “Analysis of a Bufferless OpMiGua Node”, in AICT, 2009
1 10 1001E-3
0,01
0,1
1
PLR
GST average service time, B/1
Simulation A. - Markov A. - Asymptote
When increasing the share of GST traffic RIB causes an inital rise in PLR. It is followed by a sharp drop.Approximation gives significant error when S > 0.8, but confirms trend.
0,0 0,1 0,2 0,3 0,4 0,5 0,6 0,7 0,8 0,9 1,01E-4
1E-3
0,01
PLR
Relative GST share S
Sim. - B=10 A. - Markov Sim - B=100 A. - Asymptote
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P4:OBS vs. OpMiGua
Ingress GST packets are aggregated into bursts, the aggregation process was simulated
OBS JET provides a fair comparison. Varied load, low/high priority share and switch size
OpMiGua outperforms OBS. In all the simulation cases.
Burst segmentation should reduce the difference.
- Node comparison of burst/packet loss
J. Scharf, A. Kimsås, M. Kohn and G. Hu, “OBS vs. OpMiGua - A Comparative Performance Evaluation”. ICTON, 2007
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P5: Sheduling SM packets - 4 alternatives
A. Kimsås, S. Bjørnstad, H. Øverby and N. Stol: ”Reservation Techniques in an OpMiGua Node”, ONDM, 2007
• Impeded by RIB • SM packet length is not required as input
Simple Time Window
• RIB is reduced• Complex timing using packet length as input
Length-aware Time Window
• Efficient in QoS enabled OPS, less effient for OpMiGua.• GST packets are less flexible than OPS high priority packets.
Preemption
• Mixes STW and Preemption (short FDL)• The most imminent GST arrivals are captured, preemption otherwise
Combined
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P6: Differentiated survivability - Three pragmatic alternatives
N. Stol, H. Øverby, S. Bjørnstad, A. Kimsås and A. Mykkeltveit: “Differentiated survivability in the OpMiGua Hybrid Optical network”,
in ONDM, May 2006
• SM traffic is rerouted after packet switch failure.
Duplicate PS & OXC
• If the PS fails all traffic is routed via the OXC
Duplicate OXC
• Packet switch emulates OXC behaviour for GST
• Demands additional logic for packet switch
Fallback to packet switch
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P7: Trafficability during failure
Contention resolution through preemption in a rearrangable non-blocking OPS
Compared to AWGshare the tuning range is reduced with 50% and a third switching stage is not needed.
Simulation results show that output contention dominates over internal contention.
Routing all traffic via the packet switch
A. Kimsås, H. Øverby, S. Bjørnstad and N. Stol: "Performance in a Failure Situation of an OpMiGua Packet Switch with Internal
Blocking". ICTON, 2006.
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P8: Network study A bufferless scheme using erasure codes
A. Kimsås, S. Bjørnstad, H. Øverby and N. Stol: "Improving performance in the OpMiGua hybrid network employing the network
layer packet redundancy scheme". Communications, IET, 2010.
1
i-1
i-2
2G
G-1
Unidirectional OpMiGua
ring
W = ½ ∙G∙(G-1)
EdgeEdge
Edge
Edge
Edge
Edge
Edge
EdgeEdge
EdgeEdge
Edge
Edge
i
i+1
• Redundant packets are used to retrieve lost packets
• RS, Tornado & XOR are common encoding schemes
Erasure codes
• Redundant packets are treated like SM traffic
RedSM
• Redundant packets are transmitted as low priority GST traffic.
RedGST
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P8: Network study Comparing RedGST and RedSM
A. Kimsås, S. Bjørnstad, H. Øverby and N. Stol: "Improving performance in the OpMiGua hybrid network employing the network
layer packet redundancy scheme". Communications, IET, 2010.
In presence of non-uniform traffic, the flexibility of packet switched RedSM traffic gives a smooth and predictable variation in PLR.
Spikes in PLR are caused by overloaded GST circuits. The redundancy packets newer gets transmitted from the ingress queue.
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ExtensionsIdeas for further studies
S. Bjørnstad and A. Kimsås: "Hybrid packet/time slotted circuit switched scheme (HPTS)", ICTON, 2008.
• Wavlength circuits are divided into time-slots. Slot size is limited by the allowable GST delay.
• SM traffic is oblivious to the presence of time-slots• SM packet can be placed across time-slots and guard times• Allows for looser synchronization than in traditional
networks
Time-slotted OpMiGua (HTPS)
• Polarisation switch capability (PolSC) must be distributed to other OpMiGua nodes. PolSC is not part of G.MPLS.
• Hence, extensions are required. A PolSC label is introduced to the G-MPLS label stack, between wavelength and TDM labels
G-MPLS compatibility
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Key findings
• OpMiGua outperforms OPS & OBS JET with respect to packet loss• For OpMiGua, erasure codes is a good alternative to optical buffering
Performance
• One SNB switch module can support SM & GST; without performance degradation; AWGshare is a suitable switching module.
• Low internal load in the packet switch means that one can use an internally blocking switch design. The overall penalty is low.
Node design
• Differentiated availability for GST & SM traffic is achieved by duplicating different components in the node.
Dependability
• Time-slots improves the circuit granularity; SM packets can be scheduled across timeslots and across guard-bands.
• G-MPLS cannot be used to control an OpMiGua network without extensions
Extensions
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N6: Lab implementation
GST loss could in principle occur if the SOP is poorly aligned, or due to issues in insertion logic. SM experiences contention.
using all-optical polarization labels
Ref: S. Bjørnstad, et al.: “Demonstration and analysis of TV and data transport in the OpMiGua hybrid circuit/packet switched network
testbed”, ECOC, 2007.
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N6: Physical demonstration
GST data is error free. No artifacts in video experiment.
with all optical polarization labels
Ref: S. Bjørnstad, et al.: “Demonstration and analysis of TV and data transport in the OpMiGua hybrid circuit/packet switched network
testbed”, ECOC, 2007.
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G-MPLS extentions
S. Bjørnstad and A. Kimsås: "Hybrid packet/time slotted circuit switched scheme (HPTS)", ICTON, 2008.
• SM packets are added/dropped without termination of the lambda switch path.
• Polarisation switch capability must be distributed to other OpMiGua nodes. SM add drop must be allowed for packets with this label.
Extensions are required
• Switch capability broadcast message must not interfere with non-OpMiGua nodes.
Compatibility
• Polarisation labels must be stripped off when co-operating with non-OpMiGua nodes.
• PBS must be by-passed if polarisation multiplexing is used by the upstream node.
Peaceful co-exsistence