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