mpls and traffic engineering ji-hoon yun computer communications and switching systems lab
TRANSCRIPT
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Table of contents
Introduction What is ‘traffic engineering’ ? Traffic handling in the current Internet MPLS and traffic engineering Signaling protocol Examples Conclusion
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Traffic engineering
The process of arranging how traffic flows through the network
Central goal : minimizing congestion Congestion scenarios
Network resources are insufficient Augmenting network capacity, or modulating, conditioning, or
throttling the demand Inefficient mapping of traffic onto resources
Efficient resources allocation : Traffic engineering
Another goal : reliable network operation Failure recovery
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Traffic engineering process model
Performance monitorsFault monitors
Analytical models
Formulation of control policy
Observation of network state
Characterization of traffic and network state
Performanceoptimization ?
Revisecontrol policy?
Optimize network
performance
Performance monitorsFault monitors
Analytical modelsPerformance monitors
Fault monitors
Performance monitorsFault monitors
Analytical models
Performance monitorsFault monitors
Analytical models
Capacity planningNetwork design
Network operations control
Performance monitorsFault monitors
Analytical models
Performance monitorsFault monitors
Analytical modelsCapacity augmentationConfiguration control
Yes
No
No
Yes
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Basic components of T.E.
Distribution of topology information
Path selection
Directing traffic along the computed paths
Traffic management
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Traffic handling in the current Internet
Inadequacy of measurement functions Even a traffic matrix is difficult to estimate
Limited intradomain routing control functions Destination-based Each router makes independent routing decisions Mostly shortest path routing
Drawbacks Imbalance of network load Lack of traffic management
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T.E. with the classical overlay model
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Eliminating a full mesh of adjacencies using label switching
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Traffic engineering with MPLS
Connection-oriented forwarding in an IP network Label Switched Path(LSP) Label Switched Router(LSR) Provides a method to set up explicit paths and
forward traffic on them
No addressing of how to find paths with constraints
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What does ‘multiprotocol’ mean ?
IPv6 AppleTalkIPv4 IPX
Label switching
Eth
ern
et
Fram
e R
ela
y
FD
DI
ATM
Poin
t-to-p
oin
t
Network layerprotocols
Link layerprotocols
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Connection-oriented Networks
QoS features are much easier to support All data traveling along a specific connection can be treated
similarly No special analysis needs to be done on each data packet
Each connection can be delivered along a unique path
Useful in traffic engineering Useful as a policy tool
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Connection-oriented Networks(cont’d)
High-speed service restoration for loss-sensitive services
Traffic can be redirected to other alternate connections in a very rapid fashion
In an IP network, the routing protocol must converge before service will be restored
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Components of the MPLS Traffic Engineering Model
Path management Path selection
The source router computes the complete path pruning the database to remove links that are ineligible A shortest path algorithm is then run on the pruned topology
Specifies the explicit route for an LSP tunnel Path placement
Instantiate LSP tunnels using a signaling protocol RSVP, constraint-based routed LDP(CR-LDP)
Path maintenance Sustains and terminates already established LSP tunnels
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Components of the MPLS Traffic Engineering Model (cont’d)
Traffic Assignment Partitioning ingress traffic Apportionment the partitioned traffic
Network State Information Dissemination Extension of IGP(Interior Gateway Protocol) Maximum link bandwidth, maximum reservable bandwidth,
current bandwidth reservation, resource class or color of the link, etc.
Used by constraint-based routing entities
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Components of the MPLS Traffic Engineering Model (cont’d)
Network Management Configuration management functions, performance and
accounting management functions, fault management functions
Monitoring the state of LSP and controlling their characteristics
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MPLS signaling protocols
Control-driven LSP Next hop is determined based on IP forwarding table Label Distribution Protocol (LDP)
Constraint-based Routed LSP (CR-LSP) The route is specified in the setup message May be used for traffic engineering Constraint-based routed LDP (CR-LDP), extension of RSVP
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Requirements for a Signaling Protocol
Robustness Scalability Specification of QoS LSP establishment / teardown / maintenance LSP priority / preemption Flexibility in path setup options Alternative path setup and rerouting capability
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CR-LDP vs. RSVP
CR-LDP Extension of RSVP
Transport mechanism Transport in TCP (reliable)
Raw IP packets (unreliable)
State management Hard state Soft state; needs per-flow refresh management
Messages required for LSP setup and maintenance
Request and Mapping
Path, Resv and ResvConf
Base architecture Based on LDP developed for MPLS
Based on RSVP, but may require major changes to the basic protocol to improve its scalability
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Mapping packets into LSPs - example
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Using an alternative path for reroute in IP networks
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Forwarding over the protection LSP
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Conclusion
Inadequacies of present-day IP networks
The MPLS-based solution for traffic engineering
Comparison of the two signaling protocol, RSVP and CR-LDP
MPLS coupled with the extensions of existing routing protocol and signaling protocols can provide powerful traffic engineering in ISP networks