Healing the Web:An Overview of CoDeeN & Related Projects

Vivek Pai, Larry Peterson + many othersPrinceton University

Jan 30, 2006 - GENI visit 2

How This All Started

OSDI paper on Content Distribution Network (CDN) algorithms

NS-2 simulations on 8GB AlphaServerLimits of detailed simulation – 70 hrs per experiment, huge memory requirementsStill only 1% as large as real networks

PlanetLab developedSuddenly, can get real traffic

Jan 30, 2006 - GENI visit 3

Toward a Self-Healing Web

Goals:Improve all levels of Web infrastructureInteroperate where possibleDrive with real trafficFeed back measurements

Routing

Name Lookup

Data Transfer

Replication

Client

Jan 30, 2006 - GENI visit 4

Basic CoDeeN

CoDeeN Proxy

origin

RequestRespons

e

Cache hit

Each CoDeeN proxy is a forward proxy, reverse proxy, & redirector

Cache miss

Response

Cache hit

Cache missRespons

eRequest

Cache Miss

Data Transfer

Jan 30, 2006 - GENI visit 5

By The Numbers…

Running 24/7 since June 2003*Over 1 million unique IPs as clientsAbout 20 billion requests servicedOver 25 million reqs/day

Highest-request project on PlanetLab#2 in bytes/day – we serve smaller objs

*not including PlanetLab Dec 2003 upgrade

Data Transfer

Jan 30, 2006 - GENI visit 6

Wide Area Network(WAN)

CoDNS

CoDNS

My LAN

LAN

LDNSCoDNS

My Machine

LDNS

rem

ote

answ

er

ClientPrograms

rem

ote

query

Name Lookup

Jan 30, 2006 - GENI visit 7

AvailabilityAdds one ‘9’, from 99% to

99.9%

9%

90%

99%

99.9%

99.99%

0 10 20 30 40 50 60 70 80 90

Nodes Sorted By LDNS Availability

Availab

ilit

y(%

)

CoDNS

LDNS

Name Lookup

Jan 30, 2006 - GENI visit 8

Evaluation – Live Traffic

0

100

200

300

400

500

600

700

800

900

1000

0 10 20 30 40 50 60 70 80 90

Nodes Sorted by LDNS Response Time

Av

era

ge R

esp

on

se T

ime(m

s)

LDNS

CoDNS

Name Lookup

Jan 30, 2006 - GENI visit 9

CoBlitz

Agent CDNClient

CDN reverse caches the chunks!

CDN

CDNCDN

CDN ClientAgent

CDN

chunk1

chun

k1chunk2

chunk3

chunk2

chunk5

chunk5

chunk1

chunk1

chunk4 chunk4 chunk5

chun

k5

chunk1 chunk2

chunk3 chunk3

chunk4 chunk5

CDN = Redirector + Reverse Proxy

Replication

Jan 30, 2006 - GENI visit 10

0

0.5

1

1.5

2

2.5

3

3.5

Direct BitTorrent CoBlitz

Do

wn

load

Rat

e (M

bp

s) Slowest

Median

CoBlitz Performance

CoBlitz users:CiteSeer digital libraryFedora Core LinuxPlanetLab projects

Replication

Jan 30, 2006 - GENI visit 11

PlanetSeerHost service

CDN

Components Passive monitoring

Active probing

AdvantagesLow overhead

Wide coverage

Client

A

C

B

R1

R2

Routing

Jan 30, 2006 - GENI visit 12

Confirmed Anomaly BreakdownConfirmed anomalies

271,898 in 90 days2 per minute100x more

Temp loop 1%

Path Change 44%

Fwd Outage 9%

Other Outage 23%

Persist Loop 7%

Temp Anomalies 16%

Routing

Jan 30, 2006 - GENI visit 13

Going Forward

Cycles + bandwidth + latencyqualitatively change opportunities

Obvious gains: performance, capacity, storageByzantine-like protocols become feasibleMore time for reasoning – online failure detection, repair, recoveryDeeper analysis – better classifiers, boostingBetter security – more cycles needed for crypto, dynamic SSL