Lecture 8: Testbeds

Anish Arora

CIS788.11J

Introduction to Wireless Sensor Networks

Material uses slides from Larry Peterson, Jay Lapreau, and GENI.net

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References

• EmuLab : artifact-free, auto-configured, fully controlled A configurable Internet emulator 2001: 200 nodes, 500 wires, 2x BFS (switch) 2006: 350 PCs, 7 IXPs, 40 WANodes, 27+ 802.11nodes

• PlanetLab : real environment

• GENI

• 670 machines spanning 325 sites and 35 countries

nodes within a LAN-hop of > 3M users

• Supports distributed virtualization

each of 600+ network services running in their own slice

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Emulab philosophy

• Live-network experimentation Achieves realism

Surrenders repeatability

e.g., MIT “RON” testbed, PlanetLab

• Pure emulation Introduces controlled packet loss and delay

Requires tedious manual configuration

• Emulab approach Brings simulation’s efficiency and automation to emulation

Artifact free environment

Arbitrary workload: any OS, any ”router” code, any program, for any user

So default resource allocation policy is conservative:

allocate full real node & link: no multiplexing; assume max. possible traffic

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Emulab

• Allow experimenter complete control, i.e., bare hardware with lots of tools for common cases OS’s, disk loading, state mgmt tools, IP, traffic generation,

batch, ...

• Virtualization of all experimenter-visible resources

topology, links, software, node names, network interface names, network addresses

Allows swapin/swapout • Remotely accessible• Persistent state maintenance (in database)• Separate control network• Configuration language: ns

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Experiment Life Cycle

$ns duplex-link $A $B 1.5Mbps 20ms

BA DB

A BBA

SpecificationGlobal Resource AllocationNode Self-ConfigurationExperiment ControlSwap OutParsingSwap In

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assign:Mapping Local Cluster Resources

• Maps virtual resources to local nodes and VLANs

• General combinatorial optimization approach to NP-complete problem

• Based on simulated annealing

• Minimizes inter-switch links, # switches & other constraints …

• All experiments mapped in less than 3 secs [100 nodes]

• WANassign for Mapping Global Resources (uses genetic algorithm)

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Frisbee:Disk Loading

• Loads full disk images (bulk download)• Performance techniques:

Overlaps block decompression and device I/O Uses a domain-specific algorithm to skip unused blocks Delivers images via a custom reliable multicast protocol

• 13 GB generic IDE 7200 rpm drives• Was 20 minutes for 6 GB image• Now 88 seconds

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IDE planned for Emulab

• Evolve Emulab to be the network-device-independent control and integration center for experimentation, research, development, debugging, measurement, data management, and archiving

Collaboratory: Emulab’s project abstraction

Workbench: Emulab’s experiment abstraction

Device-independent: Emulab’s builtin abstractions for

all things network-related

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Collaboratory Subsystems

• Source repository:Sourceforge, CVS, Subversion• Datapository• “My Wikis”• Mailing list(s)• Bug database• Chat/IM, chatroom management• Moodle?• Approach

Transparently do authentication, authorization and membership mgmt: “single signon”

Use separate server for information and resource security and management

Support flexible access policies: default is project-private, but project leader can change, per-subsytem Private, public read-only, public read/write

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Experimentation Workbench

• Four types: Workflow management (processes), including

Measurement and feedback steps

mandatory pipelines

Experiment management

Data management

Analyses

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Workbench: “Time Travel” and Stateful Swapout

• Time-travel of distributed systems for debugging Generalize disk image format and handling Periodic disk checkpointing Full state-save on swapout Xen-based virtual machines Challenge: network state (packets in flight)

Pragmatic approach: quiesce senders, flush buffers

• Stateful swapout/swapin [easier] Allows transparent pre-emption experiment

• Related to workbench: history, tree traversal Can share some mechanisms, some UI

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Planetlab: Requirements

1) It must provide a global platform that supports both short-term experiments and long-running services. services must be isolated from each other multiple services must run concurrently must support real client workloads

• Key Ideas Slices Virtualization

multiple architectures on a shared infrastructure Programmable

virtually no limit on new designs Opt-in on a per-user / per-application basis

attract real users demand drives deployment / adoption

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PlanetLab: Slices

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Slices

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Slices

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User Opt-in

ServerNAT

Client

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Virtualization: Per Node View

Virtual Machine Monitor (VMM)

NodeMgr

OwnerVM

VM1 VM2 VMn…

Linux kernel (Fedora Core)+ Vservers (namespace isolation)+ Schedulers (performance isolation)+ VNET (network virtualization)

Auditing serviceMonitoring servicesBrokerage servicesProvisioning services

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Global View

…

…

…

PLC

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Requirements

2) It must be available now, even though no one knows for sure what “it” is deploy what we have today, and evolve over time make the system as familiar as possible (e.g., Linux) accommodate third-party management services

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Brokerage Service

PLC(SA)

VMM

NM VM VM VM…

.

.

.

.

.

.

(broker contacts relevant nodes)

Bind(slice, pool)

VM

User BuyResources( ) Broker

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Requirements

3) Convince sites to host nodes running code written by unknown researchers from other organizations. protect the Internet from PlanetLab traffic must get the trust relationships right trusted intermediary: PLC

NodeOwner

PLCService

Developer(User)1

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3

4

1) PLC expresses trust in a user by issuing it credentials to access a slice

2) Users trust PLC to create slices on their behalf and inspect credentials

3) Owner trusts PLC to vet users and map network activity to right user

4) PLC trusts owner to keep nodes physically secure

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Requirements

4) Sustaining growth depends on support for site autonomy and decentralized control sites have final say over the nodes they host must minimize (eliminate) centralized control

• Owner autonomy owners allocate resources to favored slices owners selectively disallow unfavored slices

• Delegation PLC grants tickets that are redeemed at nodes enables third-party management services

• Federation create “private” PlanetLabs using MyPLC establish peering agreements

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Requirements

5) It must scale to support many users with minimal resources available expect under-provisioned state to be the norm shortage of logical resources too (e.g., IP addresses)

• Decouple slice creation and resource allocation given a “fair share” by default when created acquire additional resources, including guarantees

• Fair share with protection against thrashing 1/Nth of CPU 1/Nth of link bandwidth

owner limits peak rate upper bound on average rate (protect campus bandwidth)

disk quota

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GENI Design

• Key Idea Slices embedded in a substrate of networking resources

• Two central pieces Physical network substrate

expandable collection of building block components nodes / links / subnets

Software management framework knits building blocks together into a coherent facility embeds slices in the physical substrate

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National Fiber Facility

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+ Programmable Routers

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+ Clusters at Edge Sites

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+ Wireless Subnets

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+ ISP Peers

MAE-West

MAE-East

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Closer Look

Internet

backbone wavelength

backbone switch

Sensor Network

Edge SiteWireless Subnet

Customizable Router

DynamicConfigurable

Switch

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Summary of Substrate

• Node Components edge devices customizable routers optical switches

• Bandwidth national fiber facility tail circuits (including tunnels)

• Wireless Subnets urban 802.11 wide-area 3G/WiMax cognitive radio sensor net emulation

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Management Framework

GMC

Management Services

Substrate Components

- name space for users, slices, & components

- set of interfaces (“plug in” new components)

- support for federation (“plug in” new partners)

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GENI Management Core (GMC)

Resource Controller Auditing Archive

Slice ManagerGMC

nodecontrol

sensordata

CM

Virtualization SW

Substrate HW

CM

Virtualization SW

Substrate HW

CM

Virtualization SW

Substrate HW