Lecture 5 Notes

the later is what got napster killed gnutella

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Unformatted text preview: SWER SECTION:! www.google.com. ! !575157 !IN !CNAME www.l.google.com.! ! www.l.google.com. !57 !IN !A !74.125.227.49! www.l.google.com. !57 !IN !A !74.125.227.50! www.l.google.com. !57 !IN !A !74.125.227.51! www.l.google.com. !57 !IN !A !74.125.227.52! www.l.google.com. !57 !IN !A !74.125.227.48! ! ;; Query time: 26 msec! ;; SERVER: 10.0.1.1#53(10.0.1.1)! ;; WHEN: Wed Feb 1 09:31:04 2012! ;; MSG SIZE rcvd: 132! ! Emails SMTP User1 User2 ? ? Mail server Mail server Client- Server BoTlenecks •  Download )me can scale O(n) with n clients •  Scaling up server bandwidth can be expensive •  Too expensive to provision for flash crowds Peer- to- Peer Systems •  How did it start? –  A killer applica)on: file distribu)on –  Free music over the Internet! (not exactly legal…) •  Key idea: share storage, content, and bandwidth of individual users –  Lots of them •  Big challenge: coordinate all of these users –  In a scalable way (not NxN!) –  With changing popula)on (aka churn) –  With no central administra)on –  With no trust –  With large heterogeneity (content, storage, bandwidth,…) 3 Key Requirements •  P2P Systems do three things: •  Help users determine what they want –  Some form of search –  P2P version of Google •  Locate that content –  Which node(s) hold the content? –  P2P version of DNS (map name to loca)on) •  Download the content –  Should be efficient –  P2P form of Akamai Napster (1999) xyz.mp3 Napster xyz.mp3 xyz.mp3 ? Napster xyz.mp3 xyz.mp3 ? Napster xyz.mp3 xyz.mp3 ? Napster •  Search & Loca)on: central server •  Download: contact a peer, transfer directly •  Advantages: –  Simple, advanced search possible •  Disadvantages: –  Single point of failure (technical and … legal!) –  The laTer is what got Napster killed Gnutella: Flooding on Overlays (2000) •  Search & Loca)on: flooding (with TTL) •  Download: direct xyz.mp3 xyz.mp3 ? An “unstructured” overlay network Gnutella: F...
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