The World of Peer-to-Peer (P2P)/Networks and Protocols

P2P Networks and Protocols

This chapter will try to provide an overview of what is Peer-to-Peer, it's historical evolution, technologies and uses.

P2P and the Internet: A "bit" of History

P2P is not a new technology, P2P is almost as old as the Internet it started with the email and the next generation were called "metacomputing" or were classed as "middleware", the concept of it took the Internet by storm only because of a general decentralization of the P2P protocols, decentralization is the key word, not only it gives power to the simple user that is now in a leveled play field due to the easy access to powerful machines and infrastructures, but it also makes savings on information distribution resources a different approach from the old centralization concept, this can be a problem for security or control of that shared information, or in other words a "democratization" of the information (the well known use of P2P for downloading copies of MP3s, programs, and even movies from file sharing networks), and due to it's decentralizing nature the traffic patterns, are hard to predict, so, providing infrastructures to support it is a major problem most ISPs are now aware.

P2P has also been heralded as the solution to index the deep Web since most implantations of P2P technologies are based and oriented to wired networks running TCP/IP. Some are even being transfered to wireless uses (sensors, phones and robotic applications), you probably have already heard of some military implementation of intelligent mines or robotic insect hordes.

eMail

Peer2Mail

Peer to Mail ( http://www.peer2mail.com/ ) is a FreeWare application for Windows that lets you store and share files on any web-mail account, you can use Web-mail providers such as Gmail (Google Mail), Walla!, Yahoo and others, it will split the shared files into segments that will be compressed and encrypted and then sends the file segments one by one to an account you have administration access. To Download the files the process is reversed.

Security

The ecryptation was broken in Peer2Mail v1.4 (prior versions are also affected) - Peer2Mail Encrypt PassDumper Exploit.

Usenet

Usenet is the original peer to peer file-sharing application. It was originally developed to make use of UUCP (Unix to Unix Copy) to synchronize two computers' message queues. Usenet stores each article in an individual file and each newsgroup in its own directory. Synchronizing two peers is as simple as synchronizing selected directories in two disparate filesystems.

Usenet was created with the assumption that everyone would receive, store and forward the same news. This assumption greatly simplified development to the point where a peer was able to connect to any other peer in order to get news. The fragmentation of Usenet into myriad newsgroups allowed it to scale while preserving its basic architecture. 'Every node stores all news' became 'every node stores all news in newsgroups it subscribes to'.

Of all other peer-to-peer protocols, Usenet is closest to Freenet since all nodes are absolutely equal and global maps of the network are not kept by any subset of nodes. Unlike Freenet, which works by recursive pulling of a requested object along a linear chain of peers, Usenet works by recursive pushing of all news to their immediate neighbors into a tree.

FTP

The File Transfer Protocol (FTP), can be seen as a primordial P2P protocol. Even if it depends on a client/server structure the limitation is only on the type of application (client/server) one run since the roles are flexible.

Instant Messaging

Instant messaging is the act of instantly communicating between two or more people over a network (LAN or WAN). It requires the use of a client program so that when a message is sent, a notification is shown a short time after on the destination application, enabling it's user to reply to the original messages. Instant messaging allows users to send quick notes or reminders to other users in almost real time. IM can, but may not, include any other P2P service like, file-sharing, VoIP or Video Conference the broad definition is that IM is the almost instantaneous trading of messages, whatever form it takes.

Internet Relay Chat (IRC)

Internet Relay Chat, commonly abbreviated IRC is a real-time text-based multi-user communication protocol specification and implementation; it relays messages between users on the network. IRC was born sometime in 1988 according to Efnet.org ( http://efnet.org/ ). According to IRChelp.org ( http://www.irchelp.org/irchelp/rfc/ ), the official specification for IRC was written in 1993 in the RFC format. The protocol is defined in the "RFC 1459: Internet Relay Chat Protocol" is a really excellent source for both and introduction to and for detailed information about the IRC protocol. Today IRC has a very wide range of users and anyone can find a place to participate in chat.

IRC's largest unit of architecture is the IRC network. There are perhaps hundreds of IRC networks in the world each one running parallel and disjoint from the others. A client logged into one network can communicate only with other clients on the same network, not with clients on other networks. Each network is composed of one or more IRC servers. An IRC client is a program that connects to a given IRC server in order to have the server relay communications to and from other clients on the same network but not necessarily the same server.

Messages on IRC are sent as blocks. That is, other IRC clients will not see one typing and editing as one does so. One creates a message block (often just a sentence) and transmits that block all at once, which is received by the server and based on the addressing, delivers it to the appropriate client or relays it to other servers so that it may be delivered or relayed again, et cetera.

Once connected to a server, addressing of other clients is achieved through IRC nicknames. A nickname is simply a unique string of ASCII characters identifying a particular client. Although implementations vary, restrictions on nicknames usually dictate that they be composed only of characters a-z, A-Z, 0-9, underscore, and dash.

Another form of addressing on IRC, and arguably one of its defining features, is the IRC channel. IRC channels are often compared to CB Radio (Citizen's Band Radio) channels. While with CB one is said to be "listening" to a channel, in IRC one's client is said to be "joined" to the channel. Any communication sent to that channel is then "heard" or seen by the client. On the other hand, other clients on the same network or even on the same server, but not on the same channel will not see any messages sent to that channel.

Updated information on IRC can be obtained at IRC.org, the move to support IPv6 and the new technical papers, the IETF (Internet Engineering Task-Force) approved the most current technical drafts ( April 2000 - authored by C Kalt):

     RFC 2810 : IRC Architecture
     RFC 2811 : IRC Channel-Management
     RFC 2812 : IRC Client-Protocol
     RFC 2813 : IRC Server-Protocol

These documents are already available on IRC.org's official FTP-server, reachable at ftp://ftp.irc.org/irc/server

While IRC is by definition not a P2P protocol, IRC does have some extensions that support text and file transmission directly from client to client without any relay at all. These extensions are known as DCC (Direct Client Connect) and CTCP (Client To Client Protocol). For CTCP, clients like mIRC implement commands such as "ctcp nickname version" or "ctcp nickname ping" to get some interesting infos about other users.

Ident Protocol

The Ident Protocol, specified in RFC 1413, is an Internet protocol that helps identify the user of a particular TCP connection, and differentiate them from others sharing the same connection on the a server.

The Ident Protocol is designed to work it self as a server daemon, on a user's computer, where it receives requests to a specified port, generally 113. The server will then send a specially designed response that identifies the username of the current user.

Most standalone Windows machines do not have an Ident service running or present by default, in this case you may need to run your own Ident server (there are several stand alone servers available), on the other hand if you are on a Unix/Linux machine the service is there by default. Some Windows IRC clients have also an Ident server built into them.

The reason for having an running Ident server is due to some IRC servers going so far as blocking clients without an Ident response, the main reason being that it makes it much harder to connect via an "open proxy" or a system where you have compromised a single account of some form but do not have root.

Bots or Robots

IRC systems also support (ro)bots, in this case they are not real users but a collection of commands that are loaded from a script (text) file into the IRC client, or even a stand alone program that connects to a IRC channel. They serve to ease the human interaction with the system, provide some kind of automation or even to test or implement some AI.

Basic Commands

Here are some basic commands for IRC:

Command	What it does	Example
/attach /server	Sign on to a server	/attach irc.freenode.net /server irc.freenode.net
/nick	Set your nickname	/nick YourName
/join	Join a channel	/join #wikibooks
/msg	Sends a message (can either be private or to the entire channel)	Message the channel: /msg #wikibooks hello world! Send a private message: /msg JohnDoe Hi john.
/whois	Display information about a user on the server	/whois JohnDoe
/clear /clearall	Clears a channel's text. Clears all open channel's text.	/clear /clearall
/away	Sets an away message. Note: Type /away again to return from away.	/away I'm away because...
/me	Sends an action to the channel. See example.	The following: /me loves pie. would output to the chat in the case of JohnDoe: JohnDoe loves pie.

Privileged User Commands

Commands for half-operators, channel operators, channel owners, and Admins:

Command	What it does	Example
/kick	Kicks, or boots a user from the channel. You must be a half-operator or greater to do this.	Kick a user from the channel with a reason: /kick JohnDoe I kicked you because...
/ban /unban	Bans a user from the channel. You must be a channel operator or greater to do this. Unbans a user from the channel. You must be a channel operator or greater to do this.	/ban JohnDoe /unban JohnDoe

IRC Networks

• EFnet
• Undernet
• Dalnet
• Rede Portuguesa de IRC (PTnet) ( http://www.ptnet.org/ ), is the biggest Portuguese IRC network, it was created in 1997, you can get an updated list of it's server ( http://www.ptnet.org/servidores ).

Software Implementations

• KVIrc ( http://www.kvirc.net/ ) an open source (GPL) portable IRC client based on the Qt GUI toolkit and coded in C++.
• Bersirc ( http://bersirc.free2code.net/index.php/home/ ), an open source IRC client (LGPL), coded in C, that runs on Windows (Linux and Mac OS X ports under development) by utilizing the Claro GUI Toolkit.
• XChat ( http://www.xchat.org/ ) is an IRC (chat) program for Windows and UNIX (Linux/BSD) operating systems. I.R.C. is Internet Relay Chat. XChat runs on most BSD and POSIX compliant operating systems. Open Source (GPL), coded in C.
• Irssi ( http://irssi.org/ ), an IRC client program originally written by Timo Sirainen, and released under the terms of the GNU General Public License. It is written in the C programming language and in normal operation uses a text-mode user interface.
• mIRC ( http://www.mirc.co.uk/ ), a shareware Internet Relay Chat client for Windows, created in 1995 and developed by Khaled Mardam-Bey. This was originally its only use, but it has evolved into a highly configurable tool that can be used for many purposes due to its integrated scripting language.

You can also check Wikipedia list of IRC clients and Comparison of Internet Relay Chat clients (not up-to-date)...

Invisible IRC Project

A technological advancement in relation to normal IRC networks, created by invisibleNET, a research & development driven organization whose main focus is the innovation of intelligent network technology. Its goal is to provide the highest standards in security and privacy on the widely used, yet notoriously insecure Internet.

Invisible IRC Project ( http://www.invisiblenet.net/ ) is a three-tier, peer distributed network designed to be a secure and private transport medium for high speed, low volume, dynamic content. Features:

• Perfect Forward Security using Diffie-Hellman Key Exchange Protocol
• Constant session key rotation
• 128 bit Blowfish node-to-node encryption
• 160 bit Blowfish end-to-end encryption
• Chaffed traffic to thwart traffic analysis
• Secure dynamic routing using cryptographically signed namespaces for node identification
• Node level flood control
• Seamless use of standard IRC clients
• Gui interface
• Peer distributed topology for protecting the identity of users
• Completely modular in design, all protocols are plug-in capable

The IIP software is released under the GPL license and is available for Windows 98/ME/NT/2000/XP, *nix/BSD and Mac OSX, coded in C.

Other IM Networks

Software Clients

• Gaim/Pidgin ( http://pidgin.im/pidgin/home/ ) OpenSource (GPL) instant messaging client supporting Windows, GNU, BSD, and many Unix derivatives and compatible with AIM, ICQ, MSN, Yahoo!, IRC, Jabber, Gadu-Gadu, SILC, GroupWise Messenger, and Zephyr networks.
• Trillain ( http://www.ceruleanstudios.com/ ) skinnable chat client that supports AIM, ICQ, MSN, Yahoo!, and IRC, it also includes many features not included in those chat programs.

VoIP

Voice over IP can also be seen like an extension of a IM were text is substituted by live audio or video, the technological challenges are very similar, if not considering the type data of data that needs to be transfered and specific considerations due to timings. It is not uncommon for IM applications to also support VoIP or video conferencing.

Security on VoIP faces the same vulnerabilities and security threats of other P2P protocols and applications, including fuzzing, floods, spoofing, stealth attacks and VoIP spam.

BitTorrent

BitTorrent is a protocol ( Bittorrent Protocol Specification v1.0 ) created by Bram Cohen and designed to distribute primarily large computer files over the Internet, it can be used to distribute legitimate content and to enable copyright infringement on a massive scale. It is peer-to-peer in nature, as users connect to each other directly to send and receive portions of a large file from other peers who have also downloaded either the file or parts of the it. These pieces are then reassembled into the full file. Since the users are downloading from each other and not from one central server, the bandwidth load of downloading large files is divided between the many sources that the user is downloading from. This decreases the bandwidth cost for people hosting large files, and increases the download speeds for the people downloading large files, because the protocol makes use of the upstream bandwidth of every downloader to increase the effectiveness of the distribution as a whole, and to gain advantage on the part of the downloader. However, there is a central server (called a tracker) which coordinates the action of all such peers. The tracker only manages connections, it does not have any knowledge of the contents of the files being distributed, and therefore a large number of users can be supported with relatively limited tracker bandwidth. The key philosophy of BitTorrent is that users should upload (transmit outbound) at the same time they are downloading (receiving inbound.) In this manner, network bandwidth is utilized as efficiently as possible. BitTorrent is designed to work better as the number of people interested in a certain file increases, in contrast to other file transfer protocols.

BitTorrent is redefining the way people share and search for content and is getting very popular for downloading movies, TV shows, full music albums and applications (it gains in performance with other alternatives) since it is very file specific and it gains on the "new" factor of P2P content, more users equals more speed, but it will not be the optimum solution to rare files or to distribute content that is not highly sought over.

To download files that are hosted using BitTorrent users must have a BitTorrent client and to publish a file one must run a tracker.

In November 2004, BitTorrent accounted for an astounding 35 percent of all the traffic on the Internet and in 2006 the BitTorrent protocol has risen to over 60 percent of all Internet traffic according to British Web analysis firm CacheLogic. Due to this some ISPs are doing traffic shaping also know as bandwidth throttling, meaning they are reducing the protocol priority inside their networks and reducing its overall performance this has resulted in two kind of responses, some ISPs are investing in upgrading their networks and provide local cache to the protocol and implementors of the protocol are starting to battle ISPs that refuse to adapt by encrypting and randomizing it, this kick need to adapt and the increasing popularity due to deviation from its creators vision is placing more and more its evolution on the hands of independent developers.

BitTorrent ( http://www.bittorrent.com/ ) is also the name of the original implementation of the protocol it started as a Python ( source code and old versions ) application to a full featured commercial enterprise. BitTorrent.com is now a destination to download entertainment content using the BitTorrent protocol. The site provide fast, on-demand access to the most comprehensive licensed catalog of thousands of movies, TV shows, music and games, but it also provides content creators a publishing platform to list their works in high-quality alongside the most recognizable titles from major movie studios, TV networks, and record labels.

Content Indexers

Relevant Sites

Legal Torrents ( http://www.legaltorrents.com ), a collection of Creative Commons-licensed, legally downloadable, freely distributable creator-approved files, from electronic/indie music to movies and books, which have been made available via BitTorrent. Everyone that grabs the BitTorrent client and downloads helps contribute more bandwidth, because BitTorrent utilizes your unused upload bandwidth. Again, please note that all of the current torrents are made available under a Creative Commons license with the full permission of the rights holder.

bt.etree.org ( http://bt.etree.org/ ), a site provided by the etree.org community for sharing the live concert recordings of trade friendly artists.

Other:

• isoHunt ( http://isohunt.com/ ).
• The Pirate Bay ( http://thepiratebay.org ).
• mininova ( http://www.mininova.org/ ).

Protocol

BitTorrent is a protocol for distributing files. It identifies content by URL and is designed to integrate seamlessly with the web. Its advantage over plain HTTP is that when multiple downloads of the same file happen concurrently, the downloaders upload to each other, making it possible for the file source to support very large numbers of downloaders with only a modest increase in its load. ( http://www.bittorrent.com/protocol.html )

Software Implementations

Wikipedia provides an article with a Comparison of BitTorrent software.

• BitTorrent.
• BitTorrent Queue Manager ( http://btqueue.sourceforge.net/ ), a Console-based BitTorrent Client with built-in scheduler for handling multiple sessions. It is designed to manage sessions in queue easily without heavy-weight GUI. External module can search for new torrents in trackers and submit it automatically. OpenSource (Python Software Foundation License) project, using Python.
• Azureus ( http://azureus.sourceforge.net or http://www.getazureus.com/ ), an open source BitTorrent client in Java, probably the more advanced peer for the network (multiple torrent downloads, queuing/priority systems, start/stop seeding options, embedded tracker, Mainline DHT and a lot more) but a known resource hog, consuming large quantities of memory and CPU power.
• µTorrent ( http://utorrent.com ), a closed source, freeware BitTorrent client in C++, a very complete peer (includes bandwidth prioritization, scheduling, RSS auto-downloading and Mainline DHT and more) with a very low system footprint.
• BitTornado ( http://bittornado.com ), an open source BitTorrent client in Python.
• BitComet ( http://www.bitcomet.com/ ), a closed source, freeware BitTorrent client for the MS Windows OS only, it also supports HTTP/FTP download management.
• ABC [Yet Another BitTorrent Client] ( http://pingpong-abc.sourceforge.net ), an open source BitTorrent client, based on BitTornado.
• Transmission ( http://transmission.m0k.org/ ), an open source lightweight BitTorrent client with a simple graphic user interface on top of a cross-platform back-end. Transmission runs on Mac OS X with a Cocoa interface, Linux/NetBSD/FreeBSD/OpenBSD with a GTK+ interface, and BeOS with a native interface. Released under the MIT/X Consortium License.
• Warez ( http://www.warezclient.com/ ), a closed source, MS Windows only BitTorrent client from Neoteric Ltd. (previously supporting the Ares Network Warez P2P client).

Napster

The Naspter network was created at application-level using a client-server protocol over point-to-point TCP. The server was in this case a centralized directory that would hold an index of all files offered (MP3/WMA). The clients would connect to the server, identify themselves to the server (users had an account on the server) and send a list of MP3/WMA files they were sharing to it enabling other clients to search that central repository for any file on the network and then request it from any available source.

Napster protocol specifications

Opennap

Another Napster based peer-to-peer, created as open source, extending the Napster protocol to allow sharing of any media type, and adds the ability to link servers together.

Direct Connect

Direct connect is a peer-to-peer file sharing protocol/network but it uses a central server, this reliance on a central point can also be seen on the old Napster network, in that each server build an independent network (not an hybrid like for instance with eMule). One should note that some clients are now also implementing DHTs that will result in unifying used networks. The Direct Connect protocol was originally developed by Jonathan Hess for use on the Neo-Modus' Direct Connect (NMDC) v1, released September 2001 and partially in NMDC v2, released in July 2003.

Direct Connect defines the servers as HUBs. Clients connect to a central hub and that hub feature a list of clients or users connected to it. Users can then search for files to download, or as chat with other users present (on that server).

Direct Connect also implements Tiger tree hashing (TTH) for for file transfers.

NMDC Protocol

created by Jon Hess at Neo-modus protocol mirror ( http://www.teamfair.info/wiki/index.php )

ADC Protocol

The ADC protocol ( http://dcplusplus.sourceforge.net/ADC.html ) is similar to the Neo-Modus' Direct Connect (NMDC) protocol. It consists of a text protocol for a client-server network, created with goal to be simple, yet extensible.

Jon Hess contributed to the creation of this protocol with the original Direct Connect idea through the Neo-Modus Direct Connect client / hub. Other major contributing source was Jan Vidar Krey's DCTNG draft that lead to subsequent work by Dustin Brody, Walter Doekes, Timmo Stange, Fredrik Ullner, Fredrik Stenberg and others.

Client Software Implementations

• NeoModus Direct Connect
• DC++ ( http://dcpp.net/ or http://sourceforge.net/projects/dcplusplus/ ), a project aimed at producing a file sharing client using the ADC protocol. It also supports connecting to the Direct Connect network, open source under GPL, using C++/MFC running on Windows. It is developed primarily by Jacek Sieka, nicknamed arnetheduck.
• BCDC++
• CZDC++
• RevConnect ( http://www.revconnect.com/ ), supports also Kademlia, Open Source under GPL, using C++/MFC running on Windows.
• Strong DC++ ( http://strongdc.berlios.de/download.php?lang=eng ), Open Source under GPL, using C++/MFC running on Windows.
• ApexDC++ ( http://www.peerwebdc.tk/ - http://sourceforge.net/projects/apexdc/ ), based on Strong DC++. It has numerous features such as a plugin to block IP addresses (uses PeerGuardian blocklist), super seeding, customization, themes, and a nice Vista-type general user, Open Source under GPL, using C++/MFC running on Windows.

KaZaa

Software (FastTrack) Implementations

• Kazaa
• Kazaa Lite
• Diet Kaza
• giFT
• Grokster
• iMesh

JXTA

JXTA™ technology, created by Sun™ ( http://www.jxta.org ), is a set of open protocols that allow any connected device on the network ranging from cell phones and wireless PDAs to PCs and servers to communicate and collaborate in a P2P manner. JXTA peers create a virtual network where any peer may interact with other and their resources directly even when some of the peers and resources are behind firewalls and NATs or are on different network transports. The project goals are interoperability across different peer-to-peer systems and communities, platform independence, multiple/diverse languages, systems, and networks, and ubiquity: every device with a digital heartbeat. The technology is is licensed using the Apache Software License (similar to the BSD license).

Most of the implementation is done in Java (with some minor examples in C).

iFolder

iFolder ( http://www.ifolder.com ) is an still in early development open source application, developed by Novell, Inc., intended to allow cross-platform file sharing across computer networks by using the Mono/.Net framework.

iFolder operates on the concept of shared folders, where a folder is marked as shared and the contents of the folder are then synchronized to other computers over a network, either directly between computers in a peer-to-peer fashion or through a server. This is intended to allow a single user to synchronize their files between different computers (for example between a work computer and a home computer) or share files with other users (for example a group of people who are collaborating on a project).

The core of the iFolder is actually a project called Simias. It is Simias which actually monitors files for changes, synchronizes these changes and controls the access permissions on folders. The actual iFolder clients (including a graphical desktop client and a web client) are developed as separate programs that communicate with the Simias back-end.

The iFolder client runs in two operating modes, enterprise sharing (with a server) and workgroup sharing (peer-to-peer, or without a server).

Gnutella

While Gnutella is stated as a fully-distributed information-sharing technology, later versions of the protocol are a mix of centralized and distributed networks with "Servers" ( Ultra or Super peers) and "Clients" ( Leafs or Nodes ).

A Gnutella client software is basically a mini search engine (offering an alternative to web search engines) and file serving system in one.

Gnutella in new implementations also supports Tiger tree hashing (TTH) for for file transfers.

Gnutella2 ( Mike's Protocol,G2 )

The result of a fork of the Gnutella protocol, due to the failing of the developers community to reach a consensus on the evolution of the protocol.

Gnutella2 is also called Mike's Protocol since the first changes and implementation resulted from a single developer Michael Stokes. In November 2002, Michael Stokes formally and unilaterally announced the creation Gnutella2 protocol to the Gnutella Developers Forum, which caused a schism among the developers, and lead for the modifications no to be supported in several Gnutella applications since the original proposal did conflict with other vendors concepts (in specific LimeWire and Bearshare).

The now resulting implementation drops all of the old Gnutella protocol except for the connection handshake and adopts an entirely new search algorithm. Gnutella2 is often abbreviated as G2.

Software Implementations

• Deepnet Explorer ( http://www.deepnetexplorer.com/ ) a browser with RSS news reader, P2P client integration (Gnutella) and phishing alarm, closed source, Windows only, freeware.
• Shareaza ( http://shareaza.sourceforge.net/ ), Open Source (GPL), coded in C++, MFC and ATL. Multi-network peer-to-peer file-sharing client supporting Gnutella2 (G2), Gnutella, eDonkey2000/eMule, BitTorrent, FTP and HTTP protocols.
• LimeWire a peer-to-peer file sharing client for the Java Platform, Open Source (GPL), which uses the Gnutella network to locate and transfer files. It also encourages the user to pay a fee, which will then give the user access to LimeWire Pro.
• Phex
• XoloX
• Gnucleus - Gnutella, Gnutella2 (G2).
• gtk-gnutella
• FrostWire ( http://sourceforge.net/projects/frostwire/ ), a Peer to Peer (P2P) information sharing client for the Gnutella network. This project is not affiliated with LimeWire LLC. FrostWires' source code (Java) is Licensed under the GNU GPL Open Source license.
• Hydranode ( multi-protocol, referenced on the eDonkey2000/eMule section )

Ares Network

Ares (software implementation) was developed in the middle of 2002, originally using the Gnutella network. After Six months of operation, it switched to its own network comprising the leaves-and-supernodes p2p architecture. Having a protocol that can be difficult to identify made Ares at times the only P2P client that could functions on restricted networks, such as some university campuses.

Software Implementations

• Ares ( http://aresgalaxy.sourceforge.net/ ), a Chat/File Sharing P2P implementation in Delphi/Kylix. It's based on a Network organized into leafs and supernodes into a topology featuring broadcast-type searches. Ares can deliver a broader search horizon by means of the DHT technology, using a mime filter to DHT engine. Ares users can also join chat rooms or host a channel. It is for 32-bit MS Windows Operating Systems (NT/2000/XP) and Open Source under the GPL License (GNU General Public License). From version 1.9.0, data sharing was enabled between two peers behind a firewall. From version 1.9.4, Ares included support for the BitTorrent protocol. From version 1.9.9, Ares Galaxy has an experimental support for the SHOUTcast internet radio

Discontinued Implementations

• Warez P2P was a proprietary P2P filesharing service that uses the Ares network, and offers a service similar to that of Kazaa. Up to version 1.6, Warez P2P was a clone of Ares Galaxy, created by Italian developer Alberto Trevisan, but since then has been developed independently by Neoteric Ltd until recently when it was discontinued.

Freenet

• Frost (network)|Frost
• Espra

GNUnet

GNUnet ( http://gnunet.org/ ), was started in late 2001, as a framework for secure peer-to-peer networking that does not use any centralized or otherwise trusted services. A service implemented on top of the networking layer allows anonymous censorship-resistant file-sharing. GNUnet uses a simple, excess-based economic model to allocate resources. Peers in GNUnet monitor each others behavior with respect to resource usage; peers that contribute to the network are rewarded with better service.

GNUnet is part of the GNU project. Our official GNU website can be found at ( http://www.gnu.org/software/gnunet/ ), there is only an existing client, OpenSource, GPL, written in C, that shares the same name as the network. GNUnet can be downloaded from this site or the GNU mirrors.

eDonkey

eDonkey the original client for the eDonkey network (also known as eDonkey2000 network or eD2k), was created and managed by MetaMachines (Sam Yagan and Jed McCaleh) based on the city of new York. It had a stable P2P community and the protocol was older than BitTorrent it was created in 2002 shortly after the closing of Napster and competed with the FastTrack network. In June of 2005, the entertainment industry gained a victory in the Supreme Court (USA) that stated that every file-sharing developer could be sued for copyright infringement if they induced such behavior. In September 2005 the Recording Industry Association of America (RIAA) sent several commercial P2P developer cease and desist letters including to MetaMachines and with no founds to battle the interpretation of the Supreme Court decision, Sam Yagan conceded defeat as he testified to the United States Senate Judiciary Committee.

On September 11, 2006 users could not get the eDonkey2000 client software, in September 12, 2006 MetaMachines settles for $30 Million (US) and the agreement closes any avenue MetaMachines had in dealing with any P2P technology in the future...

The eDonkey networks is centralized (as it depends on serves) to provide decentralized sharing of content (not stored on the servers), there are still many software implementations that support the network the most popular is eMule.

Kademlia

Started as the Overnet project by Jed McCaleb, the creator of eDonkey2000 to overcome the need of servers. Overnet implemented the Kademlia algorithm. In late 2006, Overnet and all Overnet-owned resources were taken down as a result of legal actions from the RIAA and others. However, since the core of Overnet is decentralized, Overnet clients are still able to function with limited functionality.

The KadC library (http://kadc.sourceforge.net/ ) provides an OpenSource C library to publishing and retrieving records in Kademlia-based Distributed Hash Tables.

A some what old paper named Kademlia: A Peer-to-peer Information System Based on the XOR Metric by Petar Maymounkov and David Mazières can also be a source of information about the protocol.

The network is now known as Kademlia and is supported by many of the implementations of the old eDonkey/Overnet clients, especially by the eMule project. Kademlia is a research effort to implement a full-featured peer-to-peer system based on the XOR metric routing. Of special interest are the objectives for efficient data storage and query; anonymity; network, content and user security and authentication.

eMule content database

( http://content.emule-project.net/ ) a service provided by the eMule project team for the eDonkey2000 and Kad network users, to make free content available for download and easy to find. The content database has been on line since around new years 2004.

Software Implementations

• eMule ( http://www.emule-project.net/ ) a filesharing software implementation based on the eDonkey2000 network but offers more features than the standard client, open source C++/MFC and windows only, licensed under GPL ( http://sourceforge.net/projects/emule/ )
• Xmod ( http://savannah.nongnu.org/projects/x-mod/ ) The Xmod is a Project is based on the eMule Client, OpenSource under the GPL.
• xMule ( http://www.xmule.ws/ ), the X11 Mule, intended to bring a clone of eMule to virtually all the major Unix platforms, with a particular emphasis on Linux. C++ using wxWidgets for the GUI released as OpenSource under the GPL.
• MLdonkey ( http://mldonkey.sourceforge.net ) is a multi-platform, multi-network P2P implementation. It supports several large networks such as eDonkey, Overnet, Kademlia, Bittorrent, Gnutella (Bearshare, Limewire, etc.), Gnutella2 (Shareaza), or Fasttrack (Kazaa, Imesh, Grobster). Networks can be enabled or disabled. Searches are performed in parallel on all enabled networks. For some networks, each file can be downloaded from multiple clients concurrently.
• AMule ( http://www.amule.org/wiki/ ) a Project is based on the eMule Client, OpenSource under the GPL, currently supports Linux, FreeBSD, OpenBSD, Windows, MacOS X and X-Box on both 32 and 64 bit computers.
• eMule Bowlfish ( http://pwp.netcabo.pt/DeepSea/ ), another eMule based project that aims to provide an restricted Network solution.
• Hydranode ( http://hydranode.com/ ) a modular, plugin-driven peer-to-peer client framework which is designed with true multi-network downloads in mind (Support for eDonkey2000 and Bittorrent networks). OpenSource under the GPL, supports Linux and Windows.
• Shareaza ( multi-protocol, referenced on the Gnutella section )

Mute File Sharing

MUTE File Sharing ( http://mute-net.sourceforge.net ) is an anonymous, decentralized search-and-download file sharing system. MUTE uses algorithms inspired by ant behavior to route all messages, include file transfers, through a mesh network of neighbor connections.
Author Jason Rohrer - jcr13 (at) cornell (dot) edu Created using C++ and Crypto++ Library, support is provided for multiple OSs there is a frontend for Windows created with MFC, Mute is Open Source and released under the GPL License.

BitCoop

BitCoop (http://bitcoop.sourceforge.net/) created by Philippe Marchesseault is a console (Text Based) peer to peer backup system that enables the storage of files on remote computers with cryto and compression support. The size of files depends on the quantity you wish to share with the other peers. It is intended for server farms that wish to backup data among themselves. Supports various Operating Systems including Windows, Linux and Mac OS X, it's implemented in Java (Open Source under the GPL).

CSpace

CSpace (http://cspace.in/) provides a platform for secure, decentralized, user-to-user communication over the Internet. The driving idea behind the CSpace platform is to provide a connect(user,service) primitive, similar to the sockets API connect(ip,port). Applications built on top of CSpace can simply invoke connect(user,service) to establish a connection. The CSpace platform will take care of locating the user and creating a secure, nat/firewall friendly connection. Thus the application developers are relieved of the burden of connection establishment, and can focus on the application-level logic! CSpace is developed in Python. It uses OpenSSL for crypto, and Qt for the GUI. CSpace is licensed under the GPL.

I2P

I2P is a generic anonymous and secure peer to peer communication layer. It is a network that sits on top of another network (in this case, it sits on top of the Internet). It is responsible for delivering a message anonymously and securely to another location.

Other P2P Software Implementations

• Aimini (http://www.aimini.com/), windows freeware.

• TinyP2P ( http://www.freedom-to-tinker.com/tinyp2p.html ), claims to be The World's Smallest P2P Application, written in fifteen lines of code, in the Python programming language.

• Secure Content Downloader, closed source, Windows and Microsoft specific P2P application.

• XNap ( http://xnap.sourceforge.net/ ) OpenSource (GPL), written in Java. The client features a modern Swing based user interface and console support. Able to work in several P2P Networks OpenNap, Gnutella, Overnet and OpenFT (and other networks supported by giFT like FastTrack). It also supports ICQ and IRC, viewers for MP3 tags, images, PDF, ZIP files and Text-To-Speech.

• Napster network
  • WinMX
  • Napigator
  • FileNavigator
• WPNP network
  • WinMX

• MANOLITO network
  • Blubster
  • Piolet
• other networks
  • MojoNation
  • Carracho
  • Hotwire
  • Chord peer-to-peer lookup service|Chord
  • Dexter
  • Swarmcast
  • Alpine program|Alpine
  • Scribe
  • Groove
  • Squid_Soft|Squid
  • Akamai
  • Evernet
  • Overnet network
  • Audiogalaxy network
  • SongSpy network
  • FileTopia
  • The Circle
  • OpenFT

• Acquisition
• Cabos
• Swapper