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Berkeley COMPSCI 294 - Lecture Notes

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CS294-4 Peer-to-Peer systems IntroductionWhat is Peer-to-Peer?Is Peer-to-peer new?Why the hype???Who am I (Kubi)? OceanStore PunditUtility-based InfrastructureOceanStore: Everyone’s Data, One Big Utility “The data is just out there”OceanStore AssumptionsPowerPoint PresentationDoes Full Symmetry Make Sense? “All nodes are created equal”Possible advantages of Full SymmetryThe Path of an OceanStore UpdateCan P2P Overlay Networking Buy you Something?Enabling Technology: DOLR (Decentralized Object Location and Routing)Planetlab DOLR ServiceCan Replication be used more Effectively in Peer-to-Peer systems?Archival Dissemination of FragmentsThe Dissemination Process: Achieving Failure IndependencePeer-to-peer Goal: Stable, large-scale systemsOceanstore Observation: Want Automatic MaintenanceThe Thermodynamic AnalogyStatistical Advantage of FragmentsThe Biological InspirationThermoSpectiveWhat does this really mean?Problems?What about Game Theory?Course InformationWhat is a presentation?Why have Students Present?List of TopicsCS252/KubiatowiczLec 1.18/25/03CS294-4Peer-to-Peer systemsIntroductionAugust 25, 2003John Kubiatowicz/Anthony Josephhttp://www.cs.berkeley.edu/~kubitron/courses/cs294-4-F03CS252/KubiatowiczLec 1.28/25/03What is Peer-to-Peer?•P2P is a communications model in which each party has the same capabilities and either party can initiate a communication session. Whatis.com•P2P is a class of applications that takes advantage of resources – storage, cycles, content, human presence – available at the edges of the internet. Clay Shirky, openp2p.com•A type of network in which each workstation has equivalent capabilities and responsibilities.Webopedia.com•A P2P computer network refers to any network that does not have fixed clients and servers, but a number of peer nodes that function as both clients and servers to other nodes on the network.Wikipedia.orgCS252/KubiatowiczLec 1.38/25/03Is Peer-to-peer new?•Certainly doesn’t seem like it–What about Usenet? News groups first truly decentralized system–DNS? Handles huge number of clients–Basic IP? Vastly decentralized, many equivalent routers•One view: P2P is a reverting to the old internet–Remember? (Perhaps you don’t)–Once upon a time, all members on the internet were trusted.–Every machine had an IP address.–Every machine was a client and server.–Many machines were routers.•What is new?–Scale: people are envisioning much larger scale–Security: Systems must deal with privacy and integrity–Anonymity: Protect identity and prevent censorship–(In)Stability: Deal with unstable components as the edges»But, can systems designed this way be more stable?CS252/KubiatowiczLec 1.48/25/03Why the hype???•File Sharing: Napster (+Gnutella, KaZaa, etc)–Is this peer-to-peer? Hard to say.–Suddenly people could contribute to active global network»High coolness factor–Served a high-demand niche: online jukebox•Anonymity/Privacy/Anarchy: FreeNet, Publis, etc–Libertarian dream of freedom from the man »(ISPs? Other 3-letter agencies)–Extremely valid concern of Censorship/Privacy–In search of copyright violators, RIAA challenging rights to privacy•Computing: The Grid–Scavenge the numerous free cycles of the world to do work–Seti@Home most visible version of this•Management: Businesses–Suddenly Businesses have discovered extreme distributed computing–Does P2P mean “self-configuring” from equivalent resources?–Bound up in “Autonomic Computing Initiative”?CS252/KubiatowiczLec 1.58/25/03Who am I (Kubi)?OceanStore Pundit•Computing everywhere:–Desktop, Laptop, Palmtop–Cars, Cellphones–Shoes? Clothing? Walls? •Connectivity everywhere:–Rapid growth of bandwidth in the interior of the net–Broadband to the home and office–Wireless technologies such as CMDA, Satelite, laser•Where is persistent data????CS252/KubiatowiczLec 1.68/25/03Utility-based InfrastructurePac BellSprintIBMAT&TCanadianOceanStoreIBM•Data service provided by storage federation•Cross-administrative domain •Pay for ServiceCS252/KubiatowiczLec 1.78/25/03OceanStore: Everyone’s Data, One Big Utility “The data is just out there”•How many files in the OceanStore?–Assume 1010 people in world–Say 10,000 files/person (very conservative?)–So 1014 files in OceanStore!–If 1 gig files (ok, a stretch), get 1 mole of bytes!Truly impressive number of elements…… but small relative to physical constantsAside: new results: 1.5 Exabytes/year (1.51018)CS252/KubiatowiczLec 1.88/25/03OceanStore Assumptions•Untrusted Infrastructure: –The OceanStore is comprised of untrusted components–Individual hardware has finite lifetimes–All data encrypted within the infrastructure•Responsible Party:–Some organization (i.e. service provider) guarantees that your data is consistent and durable–Not trusted with content of data, merely its integrity•Mostly Well-Connected: –Data producers and consumers are connected to a high-bandwidth network most of the time–Exploit multicast for quicker consistency when possible•Promiscuous Caching: –Data may be cached anywhere, anytimeCS252/KubiatowiczLec 1.98/25/03Some Basic Questions aboutPeer-to-PeerCS252/KubiatowiczLec 1.108/25/03Does Full Symmetry Make Sense?“All nodes are created equal”•Most distributed algorithms need points of serialization–UseNet may be one of few classes of algorithms that don’t•Nodes have distinguished capabilities–Better Connectivity, More memory, Better management, …CS252/KubiatowiczLec 1.118/25/03Possible advantages of Full Symmetry•We will call this “purist peer-to-peer”•Anonymity/Deniability–When combined with cryptographic techniques, no distinguished nodes to go after–This is important property today!•Algorithms Easier to Analyze–Differentiation always makes things harder to analyze–Almost all recent P2P papers use Purist Assumption•How does (should?) Hierarchy and Equality interact??–This is a question we should answer by end of termCS252/KubiatowiczLec 1.128/25/03The Path of an OceanStore UpdateSecond-TierCachesMulticasttreesInner-RingServersClientsCS252/KubiatowiczLec 1.138/25/03Can P2P Overlay Networking Buy you Something?Client ServerIP NetworkTraditional SystemIP NetworkOverlayClient ServerP2P Tunneling SystemCS252/KubiatowiczLec 1.148/25/03Enabling Technology: DOLR(Decentralized Object Location and Routing)GUID1DOLRGUID1GUID2CS252/KubiatowiczLec


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Berkeley COMPSCI 294 - Lecture Notes

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