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Copyright, 1995-2008 1 ECOM6001 – Internet and the WWW Peer-to-Peer (P2P) Technologies Roger Clarke, Xamax Consultancy, Canberra Visiting Professor, CSIS,

Mar 26, 2015



  • Slide 1

Copyright, 1995-2008 1 ECOM6001 Internet and the WWW Peer-to-Peer (P2P) Technologies Roger Clarke, Xamax Consultancy, Canberra Visiting Professor, CSIS, Uni of Hong Kong Hong Kong, October 2008 Slide 2 Copyright, 1995-2008 2 Peer-to-Peer (P2P) Technologies Agenda Conventional Network Topologies, Architectures Star Topology / Master-Slave Architecture Client-Server Architecture Key Developments since the Mid-1990s Workstations Networking How and Why P2P is Unconventional Relative Equality of Nodes Node-IDs Why P2P is Attractive Technical Concerns about P2P Slide 3 Copyright, 1995-2008 3 Star Topology / Master-Slave Architecture 1950s Onwards Slide 4 Copyright, 1995-2008 4 The ARPANets Peer-to-Peer Topology 1969 Onwards Multi-Organisational Slide 5 Copyright, 1995-2008 5 The PC Era Mid-Late 1970s Onwards From Peer-to-Peer to Client-Server Personal, later Multi-Personal Slide 6 Copyright, 1995-2008 6 Client-Server Architecture mid-1980s Onwards, esp. mid-1990s Onwards Multi-Organisational Slide 7 Copyright, 1995-2008 7 Client-Server Architecture mid-1980s Onwards, esp. mid-1990s Onwards Internet-Mediated Slide 8 Copyright, 1995-2008 8 Key Developments Since the Mid- 1990s Workstation Capacity (now rivals Hosts) Workstation Diversity (vast, expanding) desktops, laptops, handhelds, smartcards,... phones, PDAs, cameras,... carburettors, fridges,... RFID tags,... Broadband Connectivity (now widespread) This enables dispersion and replication of devices capable of providing services Wireless Connectivity (rapidly increasing) This enables Mobility which means Devices change networks which means their IP-addresses change Slide 9 Copyright, 1995-2008 9 Wireless Comms Using Electromagnetic Radiation Wide Area Networks Satellite (Geosynch, Low) GS is Large footprint, very high latency (c. 2 secs) Wide Area Networks Cellular (to 20km per cell) 1 Analogue Cellular, e.g. AMPS, TACS 2 Digital Cellular, e.g. GSM, CDMA 3 3G, e.g. GSM/GPRS and W-CDMA Wide Area Networks WiMax, IEEE 802.16; iBurst Local Area Networks WiFi (10-100 m radius) e.g. IEEE 802.11x esp. 11b,g / Apple Airport Personal Area Networks (1-10 metre distance) e.g. Bluetooth (or beamed infra-red) Contactless Cards / RFID Tags / NFC (1-10 cm) Slide 10 Copyright, 1995-2008 10 Computing Power at the Edge Slide 11 Copyright, 1995-2008 11 P2P The Motivation Take advantage of resources that are available at the edges of the Internet In order to do so, make each participating program both a Client and a Server and hence each workstation acts as a host as well, e.g. a music playstation can be a mixer too your PDA can host part of a music catalogue your PC can host part of a music repository Slide 12 Copyright, 1995-2008 12 P2P Architecture Cooperative Use of Resources at the Edge Slide 13 Copyright, 1995-2008 13 A Virtual Topology The P2P Overlay Network Powerful Work-andPlay- Workstations Slide 14 Copyright, 1995-2008 14 P2P Differentiated from Client-Server Slide 15 Copyright, 1995-2008 15 P2P Towards a Technical Definition P2P is a network architecture in which each node is capable of performing each of the functions necessary to support the network and in practice many nodes do perform many of the functions Slide 16 Copyright, 1995-2008 16 The P2P Server-Components Multiple Functions Network Management Directory Management Object Management Process Management Slide 17 Copyright, 1995-2008 17 Server-Functions of a P2P Package Manage Comms with other devices Manage Directories: of Objects (e.g. files) of Services (e.g. currency conversion, or credit-card payment processes) Manage Repositories of Objects Manage Services Slide 18 Copyright, 1995-2008 18 Important Characteristics of P2P Collaboration is inherent Clients can find Servers Enough Devices with Enough Resources act as Servers for discovery, and as Servers for services Single Points-of-Failure / Bottlenecks / Chokepoints are avoided by means of networking dynamics 'Free-Riding' / 'Over-Grazing' of the 'Commons' is restrained through software and psych. features Slide 19 Copyright, 1995-2008 19 Some Characteristics of P2P Nodes A P2P node may be a device, a process, content, a person, or an identity of a person A P2P nodes availability may be unreliable or unstable (dial-up or mobile) A P2P nodes IP-Address may change (dial-up, or moving between subnets) So P2P apps commonly: build and re-build a virtual overlay network use their own addressing schemes, not the DNS Slide 20 Copyright, 1995-2008 20 Alternatives to the DNS An application-specific name-based directory (ICQ since 1996, and Groove, Napster, NetMeeting) An application-specific directory of IP- addresses without names, dynamically managed in real-time (Gnutella, Freenet) Authentication of names, and use of whatever IP-Address is advised each time they register ([email protected], PopularPower) A flexible, real-time DNS... Slide 21 Copyright, 1995-2008 21 The Scale of the Undertaking The DNS grew to c. 30 million names in 18 years from its establishment in 1984 to 2002 Napster achieved that many in 2 years The top 3 distributed-catalogue services combined quickly exceeded Napster at its peak AOL Instant Messaging is also very large The total of all P2P names may exceed 10 times the number in the DNS Slide 22 Copyright, 1995-2008 22 Categories of P2P Pure Functions, objects and the catalogue are distributed across all nodes. No one node is critical to the network's operation. Control is very difficult USENET, Fidonet, Freenet, Gnutella-1 Compromised / Two-Tier Functions and objects are highly, not fully distributed The index is highly, not fully distributed FastTrack, Gnutella-2 Hybrid Functions and objects are fully or highly distributed The index is not, e.g. it may be hierarchical (the DNS), centralised (Napster), or independent from the repository (BitTorrent) Slide 23 Copyright, 1995-2008 23 Why P2P Is Attractive Much-Reduced Dependence on individual devices and sub-networks (no central servers) Robustness not Fragility (no single point-of- failure) Resilience / Quick Recovery (inbuilt redundancy) Resistance to Denial of Service (D)DOS Attacks (no central servers) Much-Improved Scalability (proportionality) Improved Servicing of Highly-Peaked Demand (more devices on the demand-side implies there are also more server-resources) Slide 24 Copyright, 1995-2008 24 Technical Concerns about P2P Address Volatility: old addresses may not work (hence trust based on repetitive dealings is difficult) Absence of Central Control (hence risk of anarchy) Inadequate Server Participation (over- grazing) Security Challenges: Malware, embedded or infiltrated Surreptitious Enlistment (at least potential) Vulnerability to Masquerade Vulnerability to Pollution Attacks (decoys) Slide 25 Copyright, 1995-2008 25 P2P Applications Access to Digital Objects Software: Fixes/Patches Releases Virus Signatures Announcements, e.g. of technical info, business info, entertainment info, sports results, promotional messages, advertisements News Reports, by news organisations, and by members of the public Emergency Services Data Backup and Recovery Data Games Data, e.g. scenes and battle configurations Archived Messages, for conferencing/chat/IM, and cooperative publishing Learning Materials, in various formats Entertainment Materials, in various formats Slide 26 Copyright, 1995-2008 26 P2P Networks and Protocols (2005) peer#Networks.2C_protocols_and_applications BitTorrent network: ABC, Azureus, BitAnarch, BitComet, BitSpirit, BitTornado, BitTorrent, BitTorrent++, BitTorrent.Net, G3 Torrent, mlMac, MLDonkey, QTorrent, SimpleBT, Shareaza, TomatoTorrent (Mac OS X) [2], TorrentStorm eDonkey network: aMule (Linux, Mac OS X, others), eDonkey2000, eMule, LMule, MindGem, MLDonkey, mlMac, Shareaza, xMule, iMesh Light, ed2k (eDonkey 2000 protocol) FastTrack protocol: giFT, Grokster, iMesh (and its variants stripped of adware including iMesh Light), Kazaa by Sharman Networks (and its variants stripped of adware including: Kazaa Lite, K++, Diet Kaza and CleanKazaa), KCeasy, Mammoth, MLDonkey, mlMac, Poisoned Freenet network: Entropy (on its own network), Freenet, Frost Gnutella network: Acquisitionx (Mac OS X), BearShare, BetBug, Cabos, CocoGnut (RISC OS) [3], Gnucleus Grokster, iMesh, gtk-gnutella (Unix), LimeWire (Java), MLDonkey, mlMac, Morpheus, Phex Poisoned, Swapper, Shareaza, XoloX Gnutella2 network: Adagio, Caribou, Gnucleus, iMesh, MLDonkey, mlMac, Morpheus, Shareaza, TrustyFiles Joltid PeerEnabler: Altnet, Bullguard, Joltid, Kazaa, Kazaa Lite Napster network: Napigator, OpenNap, WinMX Applejuice network: Applejuice Client, Avalanche, CAKE network: BirthdayCAKE the reference implementation of CAKE, Direct Connect network: BCDC++, CZDC++, DC++, NeoModus Direct Connect, JavaDC, DCGUI-QT, HyperCast [4], Kad Network (using Kademila protocol): eMule, MindGem, MLDonkey, LUSerNet (using LUSerNet protocol): LUSerNet, MANOLITO/MP2P network: Blubster, Piolet, RockItNet, TVP2P type networks: CoolStreaming, Cybersky-TV, WPNP network: WinMX Other networks: Akamai, Alpine, ANts P2P, Ares Galaxy, Audiogalaxy network, Carracho, Chord, The Circle, Coral[5], Dexter, Diet-Agents, EarthStation 5 network, Evernet, FileTopia, GNUnet, Grapevine, Groove, Hotwire, iFolder[6], konspire2b, Madster/Aimster, MUTE, Napshare, OpenFT (Poisoned), P-Grid[7], IRC @find and XDCC, used by IRC clients including: mIRC and Trillian, JXTA, Peersites [8], MojoNation, Mnet, Overnet network, Peercasting type networks: PeerCast, IceShare - P2P implementation of IceCast, Freecast, Scour, Scribe, Skype, Solipsis a massively multi- participant virtual world, SongSpy network, Soulseek, SPIN, SpinXpress, SquidCam [9], Swarmcast, WASTE, Warez P2P, Winny, AsagumoWeb, OpenExt, Tesla, soribada, fileswapping, XSC Slide 27 Copyright, 1995-2008 27 P2P Multi-Protocol Applications (2005) http://en.wikiped