19-PeerToPeer

19-PeerToPeer - Reliable Distributed Systems Peer to Peer...

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Reliable Distributed Systems Peer to Peer
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Peer-to-Peer (p2p) Systems ± The term refers to a kind of distributed computing system in which the “main” service is provided by having the client systems talk directly to one-another ± In contrast, traditional systems are structured with servers at the core and clients around the edges
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p2p systems Standard systems: Client/Server structured P2P systems: Clients help one-another out
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An “important” topic ± … or at least, it gets a lot of press ± Recording industry claims that p2p downloads are killing profits! ± Used to be mostly file sharing, but now online radio feeds (RSS feeds) are a big deal too ± U. Wash. study showed that 80% of their network bandwidth was spent on music/video downloads! ± DVDs are largest, and accounted for the lion’s share ± A great many objects were downloaded many times ± Strangely, many downloads took months to complete… ± Most went to a tiny handful of machines in dorm rooms
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0 100 200 300 400 500 600 700 800 12:00 0:00 Mbps Wed Thu Fri Sat Sun Mon Tue WWW P2P non-HTTP TCP Akamai Breakdown of UW TCP bandwidth into HTTP Components (May 2002) WWW = 14% of TCP traffic; P2P = 43% of TCP traffic P2P dominates WWW in bandwidth consumed!! Source: Hank Levy. See http://www.cs.washington.edu/research/networking/websys/pubs/osdi_2002/osdi.pdf Where has all the bandwidth gone?
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Bandwidth Consumed by UW Servers 0 50 100 150 200 250 12:00 0:00 Mbps WWW Kazaa Gnutella Wed Thu Fri Sat Sun Mon Tue Source: Hank Levy. See http://www.cs.washington.edu/research/networking/websys/pubs/osdi_2002/osdi.pdf Bandwidth consumed by UW servers (outbound traffic)
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Byte Breakdown per Content Delivery System 0% 20% 40% 60% 80% 100% WWW Akamai Gnutella Kazaa % Bytes TEXT (T) IMAGES (I) AUDIO (A) VIDEO (V) OTHER (O) T I A V O T I A V O TI A V O A V O Source: Hank Levy. See http://www.cs.washington.edu/research/networking/websys/pubs/osdi_2002/osdi.pdf Object type for different systems
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Today: An Overview ± Today we’ll look at the area as a whole ± Origins: Illegal fire sharing ± Early academic work: “Distributed hash tables” ± Subsequent spread of field into many other areas: steganographic storage, erasure codes, gossip protocols and epidemic data dissemination, etc ± In upcoming lectures we’ll look at details of some research systems
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An old idea… ± If you think about it, most of the protocols we’ve discussed are “peer to peer” in a broad sense ± Pretty much everything Lamport was interested in uses direct client-to-client communication ± Group communication systems often do have servers, but not all need them… ± But the term really has a stronger meaning ± Denotes systems where the “data that matters” is passed among cooperating client systems ± And there may be huge numbers of clients ± Evokes image of resistance fighters working to overthrow an evil IP empire
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Attributes of p2p systems ± They can be enormous ± We often talk about hundreds of thousands or millions of client nodes, coming and going rapidly ± If there are servers, they are small in number and
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This note was uploaded on 05/13/2009 for the course CS 536 taught by Professor Sonia,f during the Fall '08 term at Purdue.

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19-PeerToPeer - Reliable Distributed Systems Peer to Peer...

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