Three case studies• peer to peer networking• wireless systems• search engines• each includes issues of– hardware processors, storage, peripherals, networks, ...representation of information, analog vs. digital, bits & bytes– softwareapplications, operating system, client-server and peer to peerorganization of information, file systems, ...algorithms: searching, sorting, compression– communications, Internet, Web, TCP/IP, protocolsbandwidth, speed, cachingcompression, error detection and correction– security and privacy; cryptography– intellectual property– social & legal & policy concernsPeer to peer networking• direct connections between peers– distributed instead of clients talking to single server– all clients provide bandwidth, storage, processing• an old idea, though with a new name– USENET news service, 1979 (still in use)• "peer-to-peer" file-sharing– centralized directories (original Napster)– decentralized directories (Gnutella, Kazaa, Limewire, Morpheus, etc.)• once a file is found somewhere– direct connection between supplier and consumer ("peers")– applications use TCP/IP (same level as HTTP, SSH, SMTP, etc.)• other examples– BitTorrent file distribution system– Skype Internet telephonyPeer to peer highlights• Napster (1999-2001) [Shawn Fanning]– centralized real-time directory, distributed files– mostly MP3 music; ideal for Ethernet bandwidths – based in USA; lawsuits put it out of business• Gnutella and friends (Grokster, Kazaa, ...)– decentralized directories: not as fast or reliable but less vulnerable to legal processes since no way to turn it off• BitTorrent (2001)– distributed directories, distributed files– distributed peer servers for load-sharing: good for movies• Digital Rights Management (DRM) systems– largely unsuccessful (awkward, inconvenient, don't really work anyway)– pay services like iTunes with reasonable DRM do better• legal action– RIAA/MPAA lawsuit put Grokster out of business (2005)– numerous lawsuit threats against students and other individuals– Viacom sues Google over YouTube postings of movies & TV programs (2007)• lobbying– numerous attempts to create more laws against file-sharingBitTorrent• file-sharing for big files in high demand• original file exists on at least one "seed" site• "tracker" server knows who has what pieces – coordinates all transfers but does not have any of the file contents• clients download blocks of file from multiple sources in parallel– blocks have cryptographic checksum to verify correct content• downloaded blocks also then uploaded to others– download rate limited by upload rate: have to contribute– tracker knows download and upload statusesbalances traffic, favors sites that are cooperating• blocks reassembled by client– when client has the whole file, it can be a seed for further transfers• much faster than single server for right kind of use– less vulnerable to flash crowds– but takes time to get started, can't do streaming, etc.Internet telephony• Voice over IP– package speech in IP packets– may connect to public telephone network on each end– strict requirements on delay (latency), jitter (variable delay),error handling, etc.• lots of commercial providers (AT&T, Cablevision, Verizon, Vonage,...)– alternative to conventional telephone service– somewhat cheaper, probably less reliable, maybe fewer services• Skype: peer to peer VoIP– comes from creators of Kazaa (!), claims no spyware or adware– free within Internet, ~2 cents/min to connect to regular phone system– 256-bit AES to encrypt each call, RSA to establish AES session key– proprietary protocol, uses both TCP and UDP– it can use your computer as a supernode (like Kazaa)– Skype bought by eBay 10/05 for $2.5B, sold again 11/09 for $2BTechnology meets law/policy/economics/politics• should there be laws controlling peer to peer technology?• should content providers like RIAA be permitted to install search (& destroy) software on home computers?• should universities be required to enforce file-sharing laws?• should VoIP be regulated by the FCC?– should VoIP suppliers have to provide services like 911?– should VoIP suppliers pay taxes and fees, and for connectivity to public telephone network?– should VoIP calls be subject to wire-tapping laws like regular phones?• should common carriers like Verizon be permitted to discriminate against traffic from other VoIP suppliers?– should there be different prices and policies for different kinds of traffic?Net neutrality• Comcast interfering with some BitTorrent traffic– claimed to be legitimate network management action to prevent a service from hogging bandwidth– when does a common carrier have the right to discriminate against some kinds of traffic to provide service to other kinds?– FCC told Comcast to stop; Comcast appealed in court (in process)• Verizon redirecting failed DNS queries to its own search page– instead of simply returning the failure status– clear violation of a standard protocol– breaks unrelated services (e.g., non-browser traffic)– overrides consumer choice of services• what regulations, if any, should there be?• Ed Felten paper: http://itpolicy.princeton.edu/pub/neutrality.pdfCopyright issues• digital media are intrinsically easy to copy– and hard to protect by technical means• peer to peer enables copyright violation on a grand scale• Digital Millennium Copyright Act (DMCA)• test cases• disclaimer– an enormous topic– IANALCopyright• protects expression, not idea• duration used to be 17 years + one renewal• now life + 70, or 95 for commercial works– (the "Mickey Mouse Protection Act", 1998)• "fair use" permits limited copying under some circumstances– criticism, comment, scholarship, research, news reporting, teaching• uncertain what fair use really is -- case by case decisions• considerations:– purpose and character of the use– nature of the copyrighted work– amount and substantiality of the portion used– effect of the use on potential market or value of copyrighted work• recent copyright laws may prevent some fair uses– can't decrypt to make excerpt for teaching or criticism– can't reverse engineer to make copies in different mediaDMCA: Digital Millennium Copyright Act (1998)• US copyright law: www.copyright.gov/title17, Chapter 12• anticircumvention: illegal to