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A Large-Scale Network Testbed. Jay Lepreau Chris Alfeld David Andersen Kevin Van Maren University of Utah http://www.cs.utah.edu/flux/testbed/ September 2, 1999. Prototype Pieces: 105 edge nodes. Experimental platforms for network and distributed systems research:.

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A Large-Scale Network Testbed

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A Large-Scale Network Testbed

Jay Lepreau Chris Alfeld

David Andersen Kevin Van Maren

University of Utah


September 2, 1999

Prototype Pieces: 105 edge nodes

Experimental platforms for network and distributed systems research:

  • Today, 3 options: simulation, small static testbeds, live networks. Each has well known limitations…

  • Hopefully someday, a large scale set of distributed small testbeds, attracting users (“Access”)

  • Soon, a new option: a medium-to-large-scale, entirely configurable testbed

  • This is a “network for research”

  • Also presents challenging research issues of its own

Some Unique Characteristics

  • Significant scale: initially 225 nodes, degree four 100Mb links between 42 core routers.

  • User-configurable control of “physical” characteristics: shaping of link latency/bandwidth/drops/errors(via invisibly interposed “shaping nodes”),router processing power, buffer space, …

  • Node breakdown: 42 core, 160 edge, 21 shaping, 2 management

A View from the Dark Side

And the Light Side

More Unique Characteristics

  • Capture of low-level node behavior such as interrupt load and memory bandwidth

  • User-replaceable node OS software

  • User-configurable physical link topology(VLAN via BFS; “P-LAN” via BFPP)

  • Completely configurable and usable by external researchers, including node power cycling

Roatan: Remote Console for a Node

Feature:Automatic mapping of desired topologies and characteristics to physical resources

  • Algorithm goals:

    • minimize likelihood of experimental artifacts (bottlenecks)

    • “optimal” packing of multiple simultaneous experiments

    • Complete in finite time!

  • Constraint-based heuristic algorithm (version 2!)

  • Feature: accepts ns-compatible specification

Early Network Configuration GUI

Research Applications

  • Simulation validation

  • Active networks

  • Resource demands of services inside routers

  • Denial-of-service resistance

  • Interaction of adaptive applications and protocols

  • All sorts of distributed system experiments

  • ...

Research Issues and Other Challenges

  • Calibration, validation, and scaling: how to emulate different speed networks? Scaling behavior of emulating faster links by slowing nodes?

  • Can we sufficiently capture real router internal behavior in a PC?

  • Assuring validity: detecting switch bottlenecks, measuring and controlling physical characteristics without introducing artifacts.

  • Algorithms and software to map requirements to resources while minimizing artifacts.

  • Integrate with ns?

  • Providing a reasonable user interface to all this.


  • Hardware and software design, remote management and GUI, mapping software vers. 1, starting to build racks

  • ~16000 lines of code so far (Tcl, C++)

  • Most of budget in place for a prototype version

Open to and Looking for...

  • Feedback

    • Examples where current methods fail and this would help

    • Examples of how this one loses! And other advice.

  • Early users

  • Collaborators on both the R and D issues of testbed

  • Shameless plugs:

    • Equipment donations (BFSwitch, esp. slightly programmable, PCs, NICs), $s

    • Utah hiring networking faculty

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