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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