Information and Computer Science Department

University of California, Irvine CA

arvindk@ics.uci.edu

The Internet has had a direct influence on millions of people by creating a global village and acting as an information super highway. There have been several "killer applications" of the Internet the first being email that provided asynchronous and instantaneous communication between individuals anywhere in the world. You could send not only text-based messages but also gifs, and several media types as attachments. The World Wide Web has entrenched the whole world in its spell and has change the way business and people communicate with each other. The popularity was essentially due to the fact that the user just needed a browser (client) to communicate with the server. Moreover the browser could be run on any OS. The web also guaranteed a uniform type for information exchange (HTTP). The other reason for its popularity includes the fact that content on the web is "On Demand" and not broadcast like normal Television/radio. The client requests from the server the information that it wants than the server sending out a standard message for all. Thus one user could be listening to pop songs while another may be downloading a research article all from the same server simultaneously.

The web is not without its disadvantages. The very fact that http is a pull protocol prevents it from sending information to clients. Consider a case where clients subscribe to listing of Microsoft stocks on the net. Now if the stock price were to dramatically fall, it would not be possible for the server to notify the client that the stocks have changed, the client needs to constantly poll the server for updates. This problem occurs as the two entities Client and Server are not the same or not peers. Enter the world of Peer to Peer computing (p2p). In p2p all the entities are peers or equals. This enables a bi-directional communication between the peers. Napster serves as archetype peer to peer application. Who would have heard about Napster and the legal issues associated with it? The chat services that are provided by some of ISPs like AIM, Yahoo Messenger, MSN Messenger, and ICQ may also be categorized as p2p applications

So what is a text book definition of p2p?

The three definitions of peer to peer are arranged in an increasing order of informality. The last definition is a succinct quintessence of Peer to Peer Computing, "Servers talking to One Another". Some of the other features of p2p include sharing of resources, accessibility of the resources from all computers etc.

Imagine a land were there are no clients and only servers. Now each entity is capable of requesting and also hosting web pages or any form of content. This enables the entities to communicate with each other in a one to one and also in many to one fashion. There is no centralized server hosting all the content and clients requesting the web pages, eliminating the necessity for finding a hosting service for web pages. An individual’s desktop could serve, as is his/ her own server. Is this all rhetoric and utopian? No. It is as simple as a mouse click!

There are lots of hazy issues that are associated with peer to peer applications.

• Protocols

• Security:

• Industry v/s Academia:

Some years back Sun Micro Systems came up with this concept of "network is the computer"^TM. In a nutshell, the PC is just an interface that the user sees and all the computing takes place behind the scenes using huge servers (running Solaris?). SUN also envisioned a web tone for a computer just as a dial tone for a telephone.

What does all this hold for peer to peer computing? In short the computers in the network as a whole are more powerful than a single computer. Lets assume that I am executing a task in my PC and my friend’s PC is idle and if there was a mechanism by which I could use his CPU time then my application could execute faster. If there were standard protocols for interaction between the computers then there could be an exponential growth in the computing power of the network as a whole. Thus if all the computers were peers and could communicate with each other then the whole network could unite to form a much more redoubtable computing machinery. Many projects have borrowed on this vision and are detailed below.

M2M (Machine to Machine)

Technology has advanced to a stage where there could be web servers in all most all the devices; several companies are developing applications where a person could control his refrigerator/oven/ music system via the Internet. It won’t be surprising if the different machines could communicate with each other. For example consider the case where the toaster from Proctor and Silex could communicate with another toaster to find out the optimum temperature for a toast. A computer automatically placing orders for inventories when the supplies are down or communicating with other suppliers to find out the nearest location where they are available. A lock in a store informing all other locks that it has been broken so that all the locks triggering a pre set reaction. This brings us to the interesting realm of Machine to Machine computing. It is estimated that this interaction would dwarf those of humans. Thus in future application would be developed for not only for people to people interaction but also between machines.

Wireless world:

Promise also holds in the wireless world with the advent of mobile IP that enable cell phones to browse the web. Would it possible for them also to run tiny little web servers that would enable them to interact with other peers. In future some of the p2p applications would enter the wireless world. Some applications like Instant Messaging have already been extended to the mobile world.

In conclusion, the success of peer to peer applications is because of the power in the form of flexibility that it gives to the user. Peer to Peer applications hold a lot of promise for the Internet and may turn out to be the next mantra of the net. However this concept is in its incipient stages and requires lot of introspection.