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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
4 3
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
3
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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