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DSRG Presentation

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A network of official Napster servers existed, but users could connect to and ... The Napster protocol was reverse engineered and became the OpenNap project. ... – PowerPoint PPT presentation

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Title: DSRG Presentation


1
DSRG Presentation
  • Presenter Bradley Momberger
  • Date April 29, 2004
  • Topic peer-to-peer network survey

2
Overview
  • P2P basics
  • Structure of p2p filesharing networks
  • Features
  • Search query structure
  • Drawbacks
  • Other p2p systems
  • P2P peer-to-peer

3
P2P Basics
  • What is P2P?
  • Internet large P2P network of the hardware
    (using TCP/IP), but software and services are
    client/server (HTTP, SMTP, NNTP, FTP, etc...p?)
  • Clients ask for a service which a server
    provides
  • P2P exists when
  • Neither side of a connection is client or server
  • DCC on IRC, traffic type is the same in each
    direction
  • Each side has both client and server capability
  • SMB, ICMP echo service, mobile ad hoc routing,
    etc.

4
A P2P Application Filesharing
  • SMB on Windows
  • One of the archetypal examples of filesharing
  • Share a drive or folder to make it accessible
    in a workgroup or domain on the local network.
  • Access other users' shared folders at any time,
    given proper credentials.
  • SMB can also be used in the client/server model,
    such as with toaster.wpi.edu

5
Pre-Napster era
  • Music file sharing grew exponentially in
    popularity from c.1996-1997
  • Coincided with popularized use of MPEG-1 Layer 3
    audio compression (MP3)
  • First MP3 offerings were usually on websites.
  • Cease desist letter campaign from RIAA shortly
    followed.
  • After websites were taken down, MP3s offered on
    FTP sites
  • Can't search FTP sites through traditional
    engines.
  • FTP search engines (like oth.net) were unreliable
    sites were highly transient or overloaded.

6
Napster
  • Napster was first released to the public in early
    1999
  • Indexed a user's collection of MP3 files and
    uploaded index to central server
  • A network of official Napster servers existed,
    but users could connect to and search only one at
    a time.
  • The Napster protocol was reverse engineered and
    became the OpenNap project.
  • OpenNap still exists today with applications such
    as WinMX (which also supports its own protocol)
  • Some networks still follow the Napster model.

7
Napster Search Structure
  • Search queries on filenames and ID3 tags (track
    information contained inside MP3 files) were sent
    to central server
  • Server processed query and returned results to
    user, including locations of represented files
  • Users connected directly with other users for
    file transfer requests
  • This was the P2P aspect of Napster

8
Napster P2P in 3 nodes
  • Essentially, file trading over Napster requires
    at least 3 nodes in the network.
  • Seeker
  • Host
  • Index Server.

9
Drawbacks of Napster
  • Single point of attack
  • A Napster-protocol network can be completely
    undone by
  • Power failure
  • Attack
  • Government intrusion
  • The network cannot operate without the central
    server.
  • An easy fallback is to let users of the network
    host the servers instead of the company, the
    many targets approach used by Direct Connect
    and WinMX.
  • A better solution exists.

10
Decentralized p2p
  • The original Internet was designed to operate
    even if large portions of it were destroyed.
  • Later generations of p2p were built around the
    same goal, namely, to be immune from outside
    attack.
  • Decentralized, or pure p2p apps are sometimes
    called second-generation p2p because they were
    a generational shift away from the Napster
    paradigm.

11
Gnutella
  • The original Gnutella client was released in
    early 2000 by Nullsoft, the AOL subsidiary
    responsible for Winamp.
  • Just as quickly, AOL forced its removal from
    download.
  • The Gnutella protocol was reverse engineered by
    several organizations and became a number of
    interoperable clients.
  • Gnutella is an example of decentralized, or
    pure p2p.

12
Gnutella Search Structure
  • A node on a Gnutella network may start a search
    query, transmit it, or answer it.
  • Since a Gnutella node is usually connected to
    more than one other node, a query that comes in
    on one channel should be transmitted to the
    others.
  • Queries are given a TTL (time-to-live) of five to
    seven hops, after which they are discarded.
  • Answers to recent queries will move backwards
    along the same path as the query itself.
  • File transfer is again done directly between two
    nodes, with a push provision for firewalls.

13
Gnutella P2P in 2 nodes
  • Without index servers, the original Gnutella
    protocol was able to perform all of its functions
    in as few as two nodes.
  • Seeker
  • Host
  • Here, two file hosts are shown on the network, in
    addition to the seeker.

14
Gnutella drawbacks
  • Citing little distinction made between users with
    large and small network resources, the original
    Gnutella network collapsed under its own weight.
  • With a TTL of 7, on a saturated network each node
    would service queries from between 75,000 and 1.2
    billion nodes.
  • Clearly all but the most endowed nodes would
    choke their bandwidth under these conditions.
  • With transient nodes, losing connection during
    download usually means incomplete files.

15
Gnutella remedies
  • Ultrapeers
  • Concentration of query passing between a smaller
    number of nodes with high bandwidth.
  • A leaf node connects to two or three ultrapeers,
    while each ultrapeer connects to several hundred
    leaves.
  • Immediate relief of the problems of network
    saturation.
  • Swarming
  • Addresses lost transfer connections by allowing a
    file to be downloaded piecemeal from multiple
    hosts.

16
Gnutella derivatives
  • Gnutella2 (Shareaza, Morpheus, giFT)
  • Created by the developers of Shareaza, Gnutella2
    adds new features to the protocol for better
    network and download performance.
  • FastTrack (KaZaA, Grokster, iMesh)
  • The most popular p2p network in the world.
  • eDonkey (eDonkey2000, eMule)
  • Not a direct derivative, but network structure is
    much the same. Root nodes in eDonkey routinely
    have 30,000 leaf nodes (up to 500,000!) as
    opposed to Gnutella2's 300-500.

17
Freenet
  • A p2p network protocol designed for anonymity and
    freedom of the press over anything else.
  • Files are hosted by the entire network instead of
    individual nodes.
  • Users host a portion of file fragments in an
    encrypted local store with no knowledge of what
    is contained therein.
  • Freenet can contain files, websites, regularly
    updated material, message boards, even other
    protocols.

18
Freenet network structure
  • Freenet servers connect to each other in a manner
    similar to Gnutella, except the addresses of
    other nodes are not communicated.
  • There is no search feature files are indexed by
    keys. A key request is passed from node to node
    with no information identifying the source.
  • Matching file fragments are returned along the
    query path. Commonly accessed fragments are
    stored on the path.

19
Freenet p2p in 1 node?
  • Locally, the server and client functions of
    FreeNet are separate applications.
  • The client makes a file request to the local
    server by key, which fills it or passes it on to
    other nodes.
  • The current generation of Freenet has a Web
    interface and a command-line Java client.

20
Freenet drawbacks
  • Lack of complete anonymity
  • While Freenet provides a reasonable level of
    anonymity, it can be broken through concerted
    detection.
  • Lack of search capability
  • The inability to search keys stems directly from
    the anonymity features of Freenet. While there
    is no inherent search, external tools allow the
    user to look up keys based on keywords.
  • Inefficiency
  • This is practically impossible to remedy.

21
Freenet similar projects
  • GNUnet
  • Official censorship-resistant p2p application
    from the GNU project
  • MNet
  • The developers of MNet consider it to be a
    distributed file store.
  • MuteNet
  • Distributed p2p application with search, but with
    file transfer relayed over search paths, masked
    host addresses, and encrypted communication
    between nodes.

22
Other p2p networks
  • Ad hoc p2p networks
  • BitTorrent
  • P2P server load balancing
  • Akamai
  • P2P Internet radio streams
  • Peercast, Allcast, Streamer
  • P2P flow of information
  • Wiki

23
BitTorrent
  • An ad hoc p2p network centered on the propagation
    of a single file.
  • A BitTorrent network has three types of nodes
  • The index server, which maintains and distributes
    a list of connected users.
  • Seeders, which have the complete file being
    transferred.
  • Leechers, who have some or no parts of the file
  • BitTorrent networks are meant to be transient
  • A file is expected to be most popular to download
    for a short time after initial release.
  • A BitTorrent network works best during this
    period, with the most number of active users.

24
Akamai
  • P2P load balancing between Web servers
  • For each client that accesses an Akamai enabled
    Web site, the request is redirected to one of a
    large pool of servers.
  • Example
  • gtnslookup www.microsoft.com
  • Name www2.microsoft.akadns.net
  • Addresses 207.46.249.252, 207.46.250.222,
    207.46.250.252, 207.46.134.221, 207.46.144.188,
    207.46.156.252, 207.46.244.188, 207.46.245.156
  • Aliases www.microsoft.com, www.microsoft.akadns.
    net
  • Use of Akamai servers allowed Microsoft's Web
    site to survive the DDoS attack caused by
    proliferation of the MyDoom worm.

25
P2P Internet radio
  • Internet radio is usually client/server in
    nature.
  • Shoutcast and RealMedia Server, for example,
    publish audio streams on the Internet.
  • The server must send a separate stream to each
    client, a bandwidth-intensive process.
  • P2P solutions, such as Peercast and Streamer,
    allow audio stream publication with less
    bandwidth.
  • Nodes accepting an audio stream also relay the
    stream to other nodes.
  • Convenient method to skirt statutory royalties,
    since the real number of listeners is unknown.

26
Wiki
  • Wiki is a method for creating information
    resources.
  • Main features
  • Open contribution by anyone
  • Attack resistance by archiving of each revision
    of each page.
  • Wiki is not p2p in terms of the network
    structure. However, the flow of information
    being any-to-any means that Wiki is a p2p
    information network.
  • The Wiki software is hosted on a Web server, but
    anyone may be an editor to the content.

27
Summary
  • P2P is...
  • Decentralization of services and data
  • Allows for network fault tolerance and efficient
    propagation of commonly accessed data.
  • A blanket term used for different approaches to
    sharing resources.
  • Operates quite often in tandem with the
    client/server model.
  • An exciting and underdeveloped field with
    applications across the realm of computer
    science.
  • Database systems are no exception!

28
Questions
  • ?

29
More information
  • http//en.wikipedia.org/wiki/Peer-to-peer
  • http//www.darkridge.com/jpr5/doc/gnutella.html
  • http//www.freenetproject.org/
  • http//en.wikipedia.org/wiki/GnuFU
  • http//wikibooks.org/wiki/P2P_File_sharing
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