Multi-Layer Traffic Engineering in IP over

Optical Networks

October 20, 2004Hung-Ying TyanDepartment of Electrical EngineeringNational Sun Yat-sen University

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Outline IP Network Transport Network Traffic Engineering

Some Observations Multi-Layer Traffic Engineering Our ML-TE Framework Our ML-TE Algorithms Evaluation

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IP Network

LAN

MAN, WAN

CompanySchoolEnterprise

CompanySchoolEnterprise

Internet Service Providers (ISP)Carriers

router

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IP Network

OXC OXC

OXC

OXC OXC

OXCOXC

(Optical) Transport Network

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IP Network over OTN

OXC OXC

OXC

OXC OXC

OXCOXC

Conceptual view

ActualIP link = circuit

Data center

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Transport Network Evolved from traditional telecommunications networks

Good at long distance transmission of digital signal

Technologies Synchronous Optical Network (SONET) Wavelength Division Multiplexing (WDM) Providing long-term circuits between end points

Separation from application networks Network on network; “overlay network” Business tiers: carriers vs ISPs

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Traffic Engineering (TE) Mechanisms to allocate network resources

according to traffic demand ISP: Make better use of resources ($$$)

Static: Network planning/provisioning/optimization

Dynamic:Resources allocation adapts to traffic change

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Dynamic TE

Basic idea:Move traffic around to alleviate congestion

Why is it effective?Data traffic can be burstySpecial events occur more frequently in data

networks

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Observations ISPs and carriers want to provide better

service with less cost

Over-provisioning because of slow response to adding capacity and large variation in traffic demandUtilization < 25%

Current dynamic TE is still limitedOnly deal with congestion

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Large Daily Traffic Variation

OC-48 link between Dallas and Washington DC

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More Observations

“Information Super Highway”?

Distribution channel of electronic information products

Electronic post office

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Technology Advances Control Plane Technology

A separate network dedicated to resources control Allows resources to be added or released quickly

Optical devices and equipments Optical laser, receiver, filter etc Wavelength conversion Optical add-drop multiplexer (OADM) Optical cross connect (OXC)

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New TE Paradigm – Multi-Layer TE

For ISP, IP links can be leased or released on demand IP network topology can be changed on demand Let IP network topology adapt to actual traffic demand

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4

3

2

2

2

Peak HoursOff-Peak Hours

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Value proposition

For ISPOPEX reduction Simplified network planning

For CarrierNew applications/customers for Carrier

Increased (overall) revenues Improved resource efficiency

More revenue from the same resources

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Network Model Two-layer overlay

IP/MPLS network Optical network

Assume that Optical TE is already available

OXC OXC

OXC

OXC OXC

OXCOXC

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Our MLTE FrameworkInput-Traffic matrix-Physical topology-etc

Initial provisioning

MPLS-TEHybrid path routing

Activatenew IP links

Remove idle IP links

under-utilization congestion

Network monitoring

noyes

Cost down?

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Network Monitoring & MPLS-TE

IP/MPLS Network

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1. Monitor outgoing IP links Detect congestion (if utilization > TH_high) Detect underutilization ( if utilization < TH_low)

2. Select target LSPs and notify ingress nodes

3. Ingress node attempts to re-route LSPs

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OXC

OXC

OXCOXC

OXC

Optical Network

IP/MPLS Network

OXC

OXC

Optical fiber

Hybrid Path Routing

Augmented topology information from optical layer: candidate links

Hybrid path consisting of Existing IP links Candidate links

Special cost functionfor both congestionand under-utilization

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DefineNetwork_Cost = sum( Link_Costi )Link_Costi = F(Link_Utilizationi) x real_link_costi

Algorithm: Triggered by congested or under-

utilized links Dijkstra’s shortest path d(link_costi)= F(expected_link_utilizationi) –

F(link_utilizationi) Granting a new route only if it decreases the real

network cost

Hybrid Path Routing

F

link_utilizationUH

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North America Model

SF

LA

Dallas

Atlanta

Miami

DC

NYC

Boston

Cleveland

DetroitChicago

Denver

Kansas City

Seattle

OXC

OXC

OXC

OXC

OXC

OXC

OXC

OXC

OXC

OXC

OXC

OXC OXCOXC

14 Nodes24 Links (fiber)193 LSPs

LSP Demand

Time (hr)

High

Low

8 160

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Experiment Results Simulation tool: J-Sim (www.j-sim.org)

North America Model14 nodes, 24 links, 193 LSPsAverage # of IP links ~ 21# of IP links at peak demand = 33Cost saving ~ 36% v.s. over-provisioning

Tradeoff between cost and number of LSP reroutes

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Visualization Tool

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Research Topics

ML-TE framework

TE operations MPLS-TE procedure and Optical-TE

Topology transformation algorithm

Hybrid path routing algorithm Suitable for both congestion and under-utilization

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Thank you!

Question?

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Initial network provisioning: Set up LSP’s for initial demand

LSP selection on the target IP link

Network monitoring

no

yes

Network cost reduced if this re-route is performed?

Hybrid path routing computation for re-routing the selected LSP

Does the hybrid path contain

“candidate links”?

Activate new IP links on those candidate links

yes

LSP rerouting

Start

Is any IP link congested or under-utilized?

yes

no

no

Remove idle IP links

yes Does the re-route result in idle IP links

in the network?

no

Basic workflow