Peer to peer networks

A peer-to-peer computer network is a network that relies primarily on the computing
power and bandwidth of the participants in the network rather than concentrating it in a relatively low number of servers. Such networks are useful for many purposes. Sharing content files containing audio, video, data or anything in digital format is very common, and realtime data, such as telephony traffic, is also passed using P2P technology.

A pure peer-to-peer network does not have the notion of clients or servers, but only equal peer nodes that simultaneously function as both "clients" and "servers" to the other nodes on the network. This model of network arrangement differs from the client-server model where communication is usually to and from a central server. A typical example for a non peer-to-peer file transfer is an FTP server where the client and server programs are quite distinct, and the clients initiate the download/uploads and the servers react to and satisfy these requests.




Some networks and channels, such as Napster and OpenNAP use a client-server structure for some tasks (e.g. searching) and a peer-to-peer structure for others. Networks such as Gnutella or Freenet use a peer-to-peer structure for all purposes, and are sometimes referred to as true peer-to-peer networks.


Classification of P2P networks

One possible classification of peer-to-peer networks is according to their degree of centralisation:

Pure peer-to-peer:
• Peers act as equals, merging the roles of clients and server
• There is no central server managing the network
• There is no central router

Hybrid peer-to-peer:
• Has a central server that keeps information on peers and responds to requests for that information.
• Peers are responsible for hosting available resources (as the central server does not have them), for letting the central server know what resources they want to share, and for making its shareable resources available to peers that request it.
• Route terminals are used addresses, which are referenced by a set of indices to obtain an absolute address.



Where P2P works:

Simple implementations that usually work for regular people. Complex instructions will cut usage. For example, setting up Napster is easy, while Gnutella (which doesn't use a centralized organizer) may need lots of understanding of IP addresses, routing, and firewalls. The implementations that must be simple include how files are uploaded off of the sharing computer. The fact that the shared copy goes to another random PC rather than a centralized server has little bearing on how easy it is. The fact that Napster has a special client-based program for uploading, like many photo web sites, is what makes it easy, not that it's P2P. Separate FTP programs or using browser primitives for uploading is not usually simple and gives uploading a bad name.

The same data on many different PCs. If only one PC has the data, access to it could be unreliable.The files are static, the information being downloaded is never changed. The files shared with Napster are not news feeds -- they are more likely the works of dead musicians.Data such that you don't mind trusting the person sharing it. If a music file for personal use was converted from CD to MP3 poorly, many people don't care. If the file being downloaded was destined for broadcast or other commercial purposes having an appropriate trust relationship with the source may be important and that complicates things and may not be practical. Lots of college students with desktops connected to local ethernets.

Where P2P probably does not work as well:

Unique content on each PC where reliability or constant availability is important. When I want your pictures I don't want to have to call you up and have you boot up your PC. (Like when you have one phone line and an old fax: call first, then tell me to connect the fax -- if I'm home -- and then call back...). Many of us live with laptops which are only connected during the day and infrequently (hopefully) at night.

Content that constantly changes. This makes the copies people recently downloaded obsolete, and effectively gets back to only one copy on one specific PC, except you may not know it.

Content that requires a trust relationship with the source. Because of the "search everywhere" nature and simple signup of Napster-style P2P, caveat emptor.
Reliable connection speed. The data you want may be on a low-speed link.


Importance of peer to peer

Peer to peer as a term has often been associated with online file sharing networks, where users trade files with one another from all over the globe. But in recent times peer to peer collaboration and the setting up of networks (both on the internet and in office intranets) has expanded to encompass a vast range of ways for people to collaborate effectively, regardless of their location.

Michel Bauwens is the founder of the Foundation For Peer To Peer Alternatives, and a strong advocate of how peer to peer is not simply a technology, but a new way of living. As the worlds of media and business shift away from a top down, hierarchical mode of operation and open up to the creativity and productivity of the public, and each individual within an organization, so society is going through necessary and timely changes.


Michel Bauwens



“The basic idea I had was that there’s a new social movement emerging which is really about extending the realm of participation to the whole of life. We live in a representative democracy, which says you can vote every four years, and choose which people will exercise power on your behalf… now we’re building tools and resources which say everybody needs to be involved, and everybody should have a voice.”

Michael Bauwens on YouTube -
http://www.youtube.com/results?search_query=michel+Bauwens&search=Search

Links of Interest

http://www.darknet.org.uk/

http://www.compinfo-center.com/int/p2p.htm

http://www.microsoft.com/technet/prodtechnol/winxppro/deploy/p2pintro.mspx