Scalability and accuracy in a large scale network emulator
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Scalability and Accuracy in a Large-Scale Network Emulator. Nov. 12, 2003 Byung-Gon Chun. Contents. Introduction Architecture Implementation and Evaluation Accuracy vs. Scalability Tradeoff Case Studies. Motivation. Real-world experiments

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Scalability and accuracy in a large scale network emulator

Scalability and Accuracy in a Large-Scale Network Emulator

Nov. 12, 2003

Byung-Gon Chun


Contents

Contents

  • Introduction

  • Architecture

  • Implementation and Evaluation

  • Accuracy vs. Scalability Tradeoff

  • Case Studies


Motivation

Motivation

  • Real-world experiments

    • It is hard to deploy and administer research software at distributed sites

    • Results are not reproducible

  • Simulation

    • It misses important real system interactions

    • Tools do not support direct execution of software

  • Emulation

    • Unmodified applications

    • Almost reproducible results

    • Important system interactions


Contribution

Contribution

  • Large-scale network emulator that can emulate network dynamics in a topology

  • Techniques to trade increased scalability for reduced accuracy

  • Evaluation of a range of systems


Architecture

Architecture

EN

VN

CR

Pipe


Modelnet phases

ModelNet Phases

  • Generate a network topology

  • Source: Internet traces, BGP dumps, Synthetic topology

  • Target: GML


Modelnet phases1

ModelNet Phases

  • Source: GML

  • Target: Pipe topology

  • Optionally, simplify the network


Modelnet phases2

ModelNet Phases

  • Map components of the distilled topology to core nodes

  • Minimize the bandwidth demands

  • Greedy algorithm


Modelnet phases3

ModelNet Phases

  • Assign VNs to ENs

  • Multiplex VNs

  • Bind an EN to a CR

  • Generate configuration scripts

  • Install pipes and routing tables to CRs

  • Set up IP addr for VNs


Core router

Core Router

  • Routing table

    • Memory vs Computation Tradeoff

  • Descriptors referencing buffered packets

  • Schedule descriptors on pipes using a heap

  • Admission control of packets injected

  • Multihop and multi-core


Discussion

Discussion

  • Resource isolation

    • UDP flows

  • Routing protocol

    • Assumes shortest path routing and instantaneous repair of node and link failures

    • Routing protocol dynamics (update propagation)

  • Flexibility to inject routing algorithms

    • Policy-based routing


Evaluation of implementation

Evaluation of Implementation

  • Accuracy - 1ms worst-case error per hop

  • Capacity

    • 120000 packets/s with 1 hop

    • 90000 packets/s with 8 hops

  • Core crossing

    • For 4 node configuration and 2 hop paths,

      0% cross-core traffic – 462.5Kpkt/s

      100% cross-core traffic – 155.8Kpkt/s

    • Depends on target topology and application communication patterns


Accuracy vs scalability tradeoffs

Accuracy vs. Scalability Tradeoffs

  • Continuum balancing accuracy and cost

  • Distillation

    • Reduce the diameter of the network

    • Hop-by-hop

    • End-to-end: bottleneck bandwidth, latency, loss rate

    • Walk-in and walk-out(?)

    • Other approaches?

    • Tradeoffs?

  • Flow-based [Narses]

  • – No wall-clock time or network size?


Accuracy vs scalability tradeoffs1

Accuracy vs. Scalability Tradeoffs


Accuracy vs scalability tradeoffs2

Accuracy vs. Scalability Tradeoffs

  • VN multiplexing

    • Howto? Mapping of multiple VNs to a EN

    • Context switch, scheduling and resource contention

    • Concurrency model

    • Number of processes  Aggregate thp. 

  • Network characteristics

    • Howto? Synthetic background cross traffic in CRs

    • Do not capture all packet dynamics (TCP slow start, bursty traffic)

    • Network change - recompute shortest paths

      • Fault injection like partitions, bandwidth change


Case studies

Case Studies

  • 10000 node gnutella network emulation

  • CFS, Replicated web services, Adaptive overlays, Ad hoc networking(?)

  • CFS: reproduce the published experimental results

  • Replicated web services: support for realistic Internet topologies and emulation of contention of shared pipes

  • Adaptive overlays: subject systems to dynamically changing network conditions


Case studies1

Case Studies


Case studies2

Case Studies


Case studies3

Case Studies


Discussion1

Discussion?


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