intro CS p2p

Introduction to Computersfor Non-EECS Major: 

Introduction to Computers for Non-EECS Major Polly Huang EE NTU http://cc.ee.ntu.edu.tw/~phuang

About Search Engine: 

About Search Engine Both Google and Yahoo (Inktomi) claim they base their searches on more than 3 billion web pages

Peer-to-Peer File Sharing: 

Peer-to-Peer File Sharing

File Sharing: 

File Sharing A straight forward term Basically users wanting to pass files around computers on the networks

The Traditional Way: 

The Traditional Way Client-server based Files are only kept in the servers Clients always get the files from the servers Never the other way around

For Example: 

For Example Downloading web pages from WWW Think the web site keeping all those pages you browse as the server Think your machine requesting pages as the client Think the pages as the shared files

The New Way: 

The New Way Peer-to-peer based Files are kept where-ever they are Each computer can download from another computer or upload files to another computer Transfers can go either way

Peer-to-peer (P2P): 

Peer-to-peer (P2P) There is no client, server distinction The computers are thus simply peers to each other Or think this way Each computer is a client and also a server

As long as I have a computer on the Internet, I can put files online for others to use.: 

As long as I have a computer on the Internet, I can put files online for others to use.

3 Major Components: 

3 Major Components Connecting Searching Downloading

Demonstration: 

Demonstration

By Example: 

By Example Napster Gnutella

Napster: 

Napster The company The technology The prospective

The Beginning: 

The Beginning January 1999 Shawn Fanning Freshman of Northeastern University If we could all share our MP3 files

The Technology: 

The Technology Connecting Through a fixed Napster server Searching Done by the Npaster server Downloading Transferred between the peers

Connecting: 

Connecting Each peer connects to a fixed Napster server somewhere Upon connecting, each peer sends its own list of files to be shared

Illustrated: 

Illustrated Napster Server Napster Server American Pie Madonna A Promise Nsync A Dance With Me J. Lo B She bangs Ricky Martin B … Reflection Christina Aguilera C Larger Than Life Backstreet Boys C …

Searching: 

Searching The peer sends the search query to the Napster server The Napster server performs the search Matching the directory The Napster server returns List of files matching the query and location of the files

Illustrated: 

Illustrated Napster Server Peer A Napster Server Peer B Peer C American Pie Madonna A Promise Nsync A Dance With Me J. Lo B She bangs Ricky Martin B … Reflection Christina Aguilera C Larger Than Life Backstreet Boys C …

Downloading: 

Downloading Select the desired file from the returned search list Request the file directly to the location indicated on the returned list

Illustrated: 

Illustrated Napster Server Peer A Napster Server Peer B Peer C American Pie Madonna A

The Prospective: 

The Prospective December 1999 The Recording Industry Association of America (RIAA) sued for copyright infringement, asking for damages of $100,000 each time a song is copied March 2001 Judge ruled for Napster to block copying of copyrighted songs July 2001 Napster file sharing service is shut down completely

Obvious Target: 

Obvious Target Being the first peer-to-peer file sharing system Supporting sharing of MP3 files

Legacy: 

Legacy Napster might be gone forever But the following peer-to-peer file sharing systems continue to prosper

Gnutella: 

Gnutella The company The technology The prospective

The Beginning: 

The Beginning Justin Frankel and Tom Petter AOL aquires Nullsoft Let’s make it really peer-to-peer

The Technology: 

The Technology Connecting Searching Downloading

Connecting: 

Connecting Each peer connects to any peer already on the Gnutella network Upon connecting, The peer announce its presence to the neighboring peers The neighboring peers propagate the announcement until it reaches all peers on the network Upon receiving the announcement The contacted peer responds with a bit of information about itself For example, number of files and amount of disk space on the particular peer to share with the network

Illustrated: 

Illustrated Peer A American Pie Madonna Promise Nsync … 10 files, 20MB Peer B Dance With Me J. Lo She bangs Ricky Martin … 20 files, 50MB Peer C Reflection Christina Aguilera Larger Than Life Backstreet Boys … 15 files, 40MB

Searching: 

Searching Similar to connecting Upon generating a search query The peer sends the search query to the neighboring peers The neighboring peers propagate the search query until it reaches all peers on the network Upon receiving the search query The contacted peer performs the search on its local file base and responds with the list of matched entries

Illustrated: 

Illustrated Peer A American Pie Madonna Promise Nsync … 10 files, 20MB Peer B Dance With Me J. Lo She bangs Ricky Martin … 20 files, 50MB Peer C Reflection Christina Aguilera Larger Than Life Backstreet Boys … 15 files, 40MB Perform Matching Perform Matching

Downloading: 

Downloading Select the desired file from the returned search list Request the file directly to the location indicated on the returned list The transfer done using HTTP Each Gnutella peer has web browser functions built-in

Illustrated: 

Illustrated Peer A American Pie Madonna Promise Nsync … 10 files, 20MB Peer B Dance With Me J. Lo She bangs Ricky Martin … 20 files, 50MB Peer C Reflection Christina Aguilera Larger Than Life Backstreet Boys … 15 files, 40MB

The Prospective: 

The Prospective Posted for one day, March 2000 Immediately withdrawn due to a major performance concern The announcements, announcement responses, search queries, and query results will all have to go around the entire network Lots of flooding If the Gnutella network is large, ouches!

The Design Lesson: 

The Design Lesson Flooding is bad P2P system designers beware And the following P2P systems continue to evolve to a better state

Napster vs. Gnutella: 

Napster vs. Gnutella Peers are connected through a Napster server Upside Requests and replies are limited within 1 hop Searching done at the potentially more powerful Napster server Search results more uniform Downside Limited amount of files shared Peers are connected directly to each other Upside Large amount of files shared Downside Flooding of requests and replies Searching done at the resource limited peer computers Search results not uniform

Minor Difference: 

Minor Difference Napster allows only MP3 file sharing Gnutella allows general file sharing

Questions?: 

Questions?