MATE:MPLS Adaptive Traffic Engineering

Anwar Elwalid Cheng Jin Steven Low Indra WidjajaBell Labs Michigan altech Fujitsu

20062006

Talk Outline

MPLS Traffic EngineeringMPLS Traffic Engineering Overview of MATEOverview of MATE Theoretical ResultsTheoretical Results Simulation ResultsSimulation Results

Best of Both Worlds

MPLS + IP form a middle ground that combines MPLS + IP form a middle ground that combines the best of IP and the best of virtual circuit the best of IP and the best of virtual circuit switching technologiesswitching technologies

ATM and Frame Relay cannot easily come to the ATM and Frame Relay cannot easily come to the middle so IP has!middle so IP has!

Label Encapsulation

MPLS – between L2 and L3MPLS – between L2 and L3 MPLS Encapsulation is specified over various MPLS Encapsulation is specified over various

media types. Top labels may use existing media types. Top labels may use existing format, lower label(s) use a new “shim” label format, lower label(s) use a new “shim” label format.format.

Label Substitution Have a friend go to B Have a friend go to B ahead of youahead of you using one of using one of

the the twotwo routing techniques routing techniques (hop-hop, source).(hop-hop, source). At At every road they reserve a lane just for you. At every road they reserve a lane just for you. At every intersection they post a big sign that says every intersection they post a big sign that says for a given lane which way to turn and what new for a given lane which way to turn and what new lane to take.lane to take.

MPLS Explicit Routing

Multiple Label-Switched Paths (LSPs) between an Multiple Label-Switched Paths (LSPs) between an ingress-egress pair can be efficiently establishedingress-egress pair can be efficiently established

The Need for Traffic Engineering No automatic load balancing among LSPsNo automatic load balancing among LSPs

Design Goals Distributed load-balancing algorithmDistributed load-balancing algorithm Need no extra network supportNeed no extra network support Minimal packet reordering requiredMinimal packet reordering required General framework for traffic engineeringGeneral framework for traffic engineering

Internet Draft: draft-widjaja-mpls-mate-02.txtInternet Draft: draft-widjaja-mpls-mate-02.txt

Two-State Adaptive Traffic Engineering

Functional Units in Ingress LSRs

Probe Probe packets are sent to estimate the packets are sent to estimate the relative relative one-one-way mean packet way mean packet delaydelay and packet and packet loss loss rate along rate along the LSPthe LSP

Traffic Engineering Problem For each Ingress-Egress pair s:For each Ingress-Egress pair s: InputInput

Offered Load: Offered Load: aass

Set of LSPs: Set of LSPs: PPs s (an LSP (an LSP pp)) OutputOutput

Vector of traffic splits: Vector of traffic splits: ss spsp = = aass

Problem Formulation Define a cost CDefine a cost Cpp , for an LSP , for an LSP pp, as a function , as a function

of link utilization of link utilization llspsp

Each ingress-egress pair minimizes the sum Each ingress-egress pair minimizes the sum of the cost function of each LSP subject to a of the cost function of each LSP subject to a feasible traffic splitfeasible traffic split

Min C(Min C(ss) = C) = Cpp ( (spsp))

s.t. s.t. spsp = = aass, , spsp > > 00

Understanding the Cost Function Not necessarily a perfect cost functionNot necessarily a perfect cost function Help steer network toward desirable Help steer network toward desirable

operating pointoperating point Allows systematic derivation and refinement Allows systematic derivation and refinement

of practical traffic engineering schemesof practical traffic engineering schemes

Solution Approach Optimality CriterionOptimality Criterion

Optimal if paths with positive flow have Optimal if paths with positive flow have minimum (and equal) cost derivativesminimum (and equal) cost derivatives

Gradient Projection AlgorithmGradient Projection Algorithm Shift traffic from paths with highest Shift traffic from paths with highest

derivatives to paths with lowest derivatives to paths with lowest derivatives by a small amount each derivatives by a small amount each iterationiteration

Asynchronous Environment Feedback delays (probe measurements):Feedback delays (probe measurements):

non-negligiblenon-negligible different delays for LSPsdifferent delays for LSPs time-varyingtime-varying

Many ingress-egress routers shift trafficMany ingress-egress routers shift traffic independentlyindependently at different timesat different times likely with different frequencieslikely with different frequencies

Convergence under AsynchronousConditions

The algorithm will converge provided the cost The algorithm will converge provided the cost function satisfies certain requirementsfunction satisfies certain requirements

Starting from any initial rate vector Starting from any initial rate vector (0), the (0), the limit point of the sequence {limit point of the sequence { (t)} is optimal, (t)} is optimal, provided the step size is sufficiently smallprovided the step size is sufficiently small

Bound on step size estimates the effect of Bound on step size estimates the effect of asynchronismasynchronism

Packet-level Discrete Event Simulator

Entities: Packets, Routers, Queues, and Entities: Packets, Routers, Queues, and LinksLinks

Simulated Functional UnitsSimulated Functional Units Measurement and AnalysisMeasurement and Analysis Traffic EngineeringTraffic Engineering Assume traffic already filtered into binsAssume traffic already filtered into bins

Both Poisson and Long-range dependent Both Poisson and Long-range dependent traffic (DAR)traffic (DAR)

Experiment Setup

Aggregate Utilization on Shared Links

Packet Loss on Shared Links

Conclusion MPLS Adaptive Traffic EngineeringMPLS Adaptive Traffic Engineering

an end-to-end solution without network an end-to-end solution without network supportsupport

distributed load-balancingdistributed load-balancing steer networks toward “optimal” steer networks toward “optimal”

operating point under asynchronous operating point under asynchronous network conditionsnetwork conditions

validated in simulationvalidated in simulation