414Lecture5

414Lecture5 - Lecture 5 Application Layer Peer-to-Peer...

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Lecture 5 Application Layer Peer-to-Peer Applications, Sockets ECSE 414 – Fall 2009
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ECSE 414, Lecture 5 2 Announcements Homework Assignment #1 due Thursday, Sep 23 Keep forming project groups and selecting topics 2010 Michael Rabbat
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ECSE 414, Lecture 5 3 Topics for Today Peer-to-peer applications Application programming with Sockets 2010 Michael Rabbat
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ECSE 414, Lecture 5 4 Comparing Client-server, P2P architectures Question : How much time distribute file initially at one server to N other computers? u s u 2 d 1 d 2 u 1 u N d N Server Network (with abundant bandwidth) File, size F u s : server upload bandwidth u i : client/peer i upload bandwidth d i : client/peer i download bandwidth 2010 Michael Rabbat
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5 Client-server: file distribution time u s u 2 d 1 d 2 u 1 u N d N Server Network (with abundant bandwidth) F server sequentially sends N copies: NF/u s time client i takes F/d i time to download increases linearly in N (for large N) = d cs = max { , F/min(d i ) } i Time to distribute to N clients using client/server approach 2010 Michael Rabbat
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ECSE 414, Lecture 5 6 P2P: file distribution time u s u 2 d 1 d 2 u 1 u N d N Server Network (with abundant bandwidth) F server must send one copy: F /u s time client i takes F/d i time to download NF bits must be downloaded (aggregate) fastest possible upload rate (assuming all nodes sending file chunks to same peer): u s + Σ u i i=1,N d P2P max { F/u , F/min(d i ) , NF/(u s + Σ u i) } i sublinear in N 2010 Michael Rabbat
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Comparing Client-server, P2P architectures
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ECSE 414, Lecture 5 8 P2P Case Study: BitTorrent tracker: tracks peers participating in torrent torrent: group of peers exchanging chunks of a file obtain list of peers trading chunks peer P2P file distribution 2010 Michael Rabbat
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ECSE 414, Lecture 5 9 BitTorrent (1) file divided into 256KB chunks . peer joining torrent: has no chunks, but will accumulate them over time registers with tracker to get list of peers, connects to subset of peers (“neighbors”) while downloading, peer uploads chunks to other peers. peers may come and go once peer has entire file, it may (selfishly) leave or (altruistically) remain 2010 Michael Rabbat
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ECSE 414, Lecture 5 10 BitTorrent (2) Pulling Chunks at any given time, different peers have different subsets of file chunks periodically, a peer (Alice) asks each neighbor for list of chunks that they have. Alice issues requests for
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This note was uploaded on 05/09/2011 for the course ECSE 414 taught by Professor Rabbat during the Fall '10 term at McGill.

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414Lecture5 - Lecture 5 Application Layer Peer-to-Peer...

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