Peer-to-peer systems”Sharing is caring”

Why P2P?Client-server systems limited by

management and bandwidthP2P uses network resources at

the edges

Characteristics of P2PAll nodes have the same

capabilities and responsibilitiesNo central control neededOffers more or less anonymityData placement algorithmDoes not rely on any one node

Early useXerox GrapevineLamport’s algorithm, Bayou

storage system and classless interdomain IP routing algorithm

Need a large number of broadband users

1999 in the US and by 2004 worldwide with over 100 million users

Next generationThree generations of P2P

systemsNapsterSecond generation – large

improvements. Freenet or KazaaP2P middleware – Pastry and

Tapestry

NapsterCreated in 1999 by Shawn

FanningCentralized indexShut down 2001

Routing overlay and GUIDNetwork in the application layerGlobally Unique IdentifiersAddition and removalSecure against tamperingSpreads out the GUIDBittorrent and trackers

Middleware – PastryPrefix routing128-bit GUIDNo clashingUses UDPSets up routing table using GUID

and IP

Middleware – TapestryMessage distribution similar to

PastryDOLR (Distributed Object

Location and Routing)Replicas160-bit

Unstructured P2PNo structure for placement,

routing or searchingNo topological orderAd hocConnect to nearest neighbourFlooding