PlanetLab: Evolution vs Intelligent Design in Global

Network Infrastructure

Larry PetersonPrinceton University

Case for PlanetLab

This chasm is a majorbarrier to realizing the

Future InternetMat

uri

ty

Time

FoundationalResearch

Simulation andResearch Prototypes

Small ScaleTestbeds

DeployedFuture

Internet

PlanetLab

QuickTime™ and aTIFF (Uncompressed) decompressor

are needed to see this picture.

QuickTime™ and aTIFF (Uncompressed) decompressor

are needed to see this picture.

• 637 machines spanning 302 sites and 35 countries nodes within a LAN-hop of > 2M users

• Supports distributed virtualization each of 350+ network services running in their own slice

Slices

Slices

Slices

User Opt-in

ServerNAT

Client

Per-Node View

Virtual Machine Monitor (VMM)

NodeMgr

LocalAdmin

VM1 VM2 VMn…

Long-Running Services• Content Distribution

– CoDeeN: Princeton– Coral: NYU– Cobweb: Cornell

• Internet Measurement– ScriptRoute: Washington, Maryland

• Anomaly Detection & Fault Diagnosis– PIER: Berkeley, Intel– PlanetSeer: Princeton

• DHT– Bamboo (OpenDHT): Berkeley, Intel– Chord (DHash): MIT

Services (cont)• Routing

– i3: Berkeley– Virtual ISP: Princeton

• DNS– CoDNS: Princeton– CoDoNs: Cornell

• Storage & Large File Transfer– LOCI: Tennessee– CoBlitz: Princeton– Shark: NYU

• Multicast– End System Multicast: CMU– Tmesh: Michigan

Usage Stats• Slices: 350 - 425• AS peers: 6000• Users: 1028• Bytes-per-day: 2 - 4 TB• IP-flows-per-day: 190M• Unique IP-addrs-per-day: 1M

Architectural Questions• What is the PlanetLab architecture?

– more a question of synthesis than cleverness• Why is this the right architecture?

– non-technical requirements– technical decisions that influenced adoption

• What is a system architecture anyway?– how does it accommodate change (evolution)

Requirements

1) Global platform that supports both short-term experiments and long-running services.

– services must be isolated from each other• performance isolation• name space isolation

– multiple services must run concurrently

Distributed Virtualization– each service runs in its own slice: a set of VMs

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)

Unbundled Management– independent mgmt services run in their own slice– evolve independently; best services survive– no single service gets to be “root” but some services

require additional privilege

Requirements

3) Must convince sites to host nodes running code written by unknown researchers.

– protect the Internet from PlanetLab

Chain of Responsibility– explicit notion of responsibility– trace network activity to responsible party

Requirements

4) Sustaining growth depends on support for autonomy and decentralized control.

– sites have the final say about the nodes they host– sites want to provide “private PlanetLabs”– regional autonomy is important

Federation– universal agreement on minimal core (narrow waist)– allow independent pieces to evolve independently– identify principals and trust relationships among them

Requirements5) 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 from resource allocationOverbook with recovery

– support both guarantees and best effort– recover from wedged states under heavy load

Tension Among Requirements• Distributed Virtualization / Unbundled Management

– isolation vs one slice managing another

• Federation / Chain of Responsibility– autonomy vs trusted authority

• Under-provisioned / Distributed Virtualization– efficient sharing vs isolation

• Other tensions– support users vs evolve the architecture– evolution vs clean slate

Synergy Among Requirements• Unbundled Management

– third party management software

• Federation– independent evolution of components– support for autonomous control of resources

Architecture (1)• Node Operating System

– isolate slices– audit behavior

• PlanetLab Central (PLC)– remotely manage nodes– bootstrap service to instantiate and control slices

• Third-party Infrastructure Services– monitor slice/node health– discover available resources– create and configure a slice– resource allocation

Trust RelationshipsPrincetonBerkeleyWashingtonMITBrownCMUNYUETHHarvardHP LabsIntelNEC LabsPurdueUCSDSICSCambridgeCornell…

princeton_codeennyu_dcornell_beehiveatt_mcashcmu_esmharvard_icehplabs_donutlabidsl_pseprirb_phiparis6_landmarksmit_dhtmcgill_cardhuji_enderarizona_storkucb_bambooucsd_shareumd_scriptroute…

N x NTrusted

Intermediary(PLC)

Trust Relationships (cont)

NodeOwner

PLCService

Developer(User)1

2

3

4

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

2) Users trust 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

Trust Relationships (cont)

NodeOwner

MgmtAuthority

ServiceDeveloper

(User)1

2

3

4

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

2) Users trust 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

SliceAuthority

5

6

5) MA trusts SA to reliably map slices to users

6) SA trusts MA to provide working VMs

Owner 1

Owner 2

Owner 3

Owner N

. . .

SliceAuthority

ManagementAuthority

Software updates

Auditing data

Create slices

. .

.

U S

E R

S

PlanetLabNodes

ServiceDevelopers

Request a slice

New slice ID

Access slice

Identifyslice users(resolve abuse)

Learn about nodes

Architecture (2)

Architecture (3)

Node

MA

NM +VMM

nodedatabase

NodeOwner

OwnerVM

SCS

SAslicedatabase

VM ServiceDeveloper

Per-Node Mechanisms

Virtual Machine Monitor (VMM)

NodeMgr

OwnerVM

VM1 VM2 VMn…

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

SliverMgrProper

PlanetFlowSliceStatpl_scspl_mom

VMM• Linux

– significant mind-share• Vserver

– scales to hundreds of VMs per node (12MB each)• Scheduling

– CPU• fair share per slice (guarantees possible)

– link bandwidth• fair share per slice• average rate limit: 1.5Mbps (24-hour bucket size)• peak rate limit: set by each site (100Mbps default)

– disk• 5GB quota per slice (limit run-away log files)

– memory• no limit• pl_mom resets biggest user at 90% utilization

VMM (cont)• VNET

– socket programs “just work”• including raw sockets

– slices should be able to send only…• well-formed IP packets• to non-blacklisted hosts

– slices should be able to receive only…• packets related to connections that they initiated (e.g., replies)• packets destined for bound ports (e.g., server requests)

– essentially a switching firewall for sockets• leverages Linux's built-in connection tracking modules

– also supports virtual devices• standard PF_PACKET behavior• used to connect to a “virtual ISP”

Node Manager• SliverMgr

– creates VM and sets resource allocations– interacts with…

• bootstrap slice creation service (pl_scs)• third-party slice creation & brokerage services (using tickets)

• Proper: PRivileged OPERations– grants unprivileged slices access to privileged info– effectively “pokes holes” in the namespace isolation– examples

• files: open, get/set flags• directories: mount/unmount• sockets: create/bind• processes: fork/wait/kill

Auditing & Monitoring• PlanetFlow

– logs every outbound IP flow on every node• accesses ulogd via Proper• retrieves packet headers, timestamps, context ids (batched)

– used to audit traffic– aggregated and archived at PLC

• SliceStat– has access to kernel-level / system-wide information

• accesses /proc via Proper

– used by global monitoring services– used to performance debug services

Infrastructure Services• Brokerage Services

– Sirius: Georgia– Bellagio: UCSD, Harvard, Intel– Tycoon: HP

• Environment Services– Stork: Arizona– AppMgr: MIT

• Monitoring/Discovery Services– CoMon: Princeton– PsEPR: Intel– SWORD: Berkeley– IrisLog: Intel

Evolution vs Intelligent Design• Favor evolution over clean slate• Favor design principles over a fixed architecture• Specifically…

– leverage existing software and interfaces– keep VMM and control plane orthogonal– exploit virtualization

• vertical: mgmt services run in slices• horizontal: stacks of VMs

– give no one root (least privilege + level playing field)– support federation (decentralized control)

Other Lessons

• Inferior tracks lead to superior locomotives• Empower the user: yum• Build it and they (research papers) will come• Overlays are not networks• PlanetLab: We debug your network• From universal connectivity to gated communities• If you don’t talk to your university’s general

counsel, you aren’t doing network research• Work fast, before anyone cares

Collaborators• Andy Bavier• Marc Fiuczynski• Mark Huang• Scott Karlin• Aaron Klingaman• Martin Makowiecki• Reid Moran• Steve Muir• Stephen Soltesz• Mike Wawrzoniak

• David Culler, Berkeley• Tom Anderson, UW• Timothy Roscoe, Intel• Mic Bowman, Intel• John Hartman, Arizona• David Lowenthal, UGA• Vivek Pai, Princeton• David Parkes, Harvard• Amin Vahdat, UCSD• Rick McGeer, HP Labs

Available CPU Capacity

0

20

40

60

80

100

120

10 20 30 40 50 60 70 80

Pct of CPU Available

Pct of 360 Nodes

Feb 1-8, 2005 (Week before SIGCOMM deadline)

Node Boot/InstallNode PLC (MA) Boot Server

1. Boots from BootCD (Linux loaded)

2. Hardware initialized

3. Read network config . from floppy

7. Node key read into memory from floppy

4. Contact PLC (MA)

6. Execute boot mgr

Boot Manager

8. Invoke Boot API

10. State = “install”, run installer

11. Update node state via Boot API

13. Chain-boot node (no restart)

14. Node booted

9. Verify node key, send current node state

12. Verify node key, change state to “boot”

5. Send boot manager

Chain of ResponsibilityJoin Request PI submits Consortium paperwork and requests to join

PI Activated PLC verifies PI, activates account, enables site (logged)

User Activated Users create accounts with keys, PI activates accounts (logged)

Nodes Added to Slices

Users add nodes to their slice (logged)

Slice Traffic Logged

Experiments generate traffic (logged by PlanetFlow)

Traffic Logs Centrally Stored

PLC periodically pulls traffic logs from nodes

Slice Created PI creates slice and assigns users to it (logged)

Network Activity Slice Responsible Users & PI

Slice Creation

PLC(SA)

VMM

NM VM

PI SliceCreate( ) SliceUsersAdd( )

User SliceAttributeSet( ) SliceGetTicket( )

VM VM…

.

.

.

.

.

.

(distribute ticket to slice creation service: pl_scs)

SliverCreate(rspec)

Brokerage Service

PLC(SA)

VMM

NM VMSliceAttributeSet( ) SliceGetTicket( ) VM VM…

.

.

.

.

.

.

(distribute ticket to brokerage service)

rcap = PoolCreate(rspec)

Broker

Brokerage Service (cont)

PLC(SA)

VMM

NM VM VM VM…

.

.

.

.

.

.

(broker contacts relevant nodes)

PoolSplit(rcap, slice, rspec)

VM

User BuyResources( ) Broker