What are the legal uses of peer to peer networking?

Answer 1

This question confuses two completely different things. One is whether it is legal to use a particular application in a particular way. The other is whether an application is organized as peer-to-peer or some other way, such as client-server or master-slave. Whether an application is peer-to-peer has nothing to do with whether it is legal to use an application in a particular way.

A peer-to-peer application is an networked application where none of the processes in the application is inherently controlled by any other process in the application. Contrast this with a client-server application, where a client makes requests of a server (which the server can honor or not as it sees fit), or a master-slave application, where a controlling process (the master) issues instructions to one or more controlled processes (the slaves). The most popular applications that we use on the internet today tend to be client-server or master-slave applications, but applications do not inherently need to work this way. Consider for example a telephone or instant messaging program that allows users at two different computers to talk (via voice or text) to each other. Each computer can independently send messages (voice or text) to the other one. Many kinds of IM and telephony applications are set up as client-server (whether the server mediates between clients in some way) but one advantage of implementing these applications as peer-to-peer is that no central server is needed.

Peer-to-peer applications have undeservedly developed a bad reputation for several reasons. One is that some popular peer-to-peer applications have been widely used to transfer copyrighted material. Yes, it's illegal (in most countries) to transfer copyrighted material without permission - but it doesn't matter whether this is done using a peer-to-peer program, or a client-server program, or a USB thumb drive. Copying of copyrighted material is illegal no matter how you do it.

Another reason peer-to-peer apps have developed a bad reputation is that peer-to-peer applications don't care which end established a networking connection. Once the connection between two peers is established, either peer may make requests of the other. Many sites naively rely on "firewalls" to protect their computers from attack. A common policy is to block all connections that are being initiated from outside the firewall, on the theory that requests can only come from the party that initiated the network connection. Many client-server applications work this way, but this is not true for networked applications in general. Sites that naively rely on firewalls to protect their network may categorically object to usage of peer-to-peer programs since their firewalls will not protect them.

Fortunately, the advantages of peer-to-peer applications are becoming more widely understood and acceptance of peer-to-peer as a legitimate organizing principle for networked applications is increasing.

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Answer 2

there are no illegal uses. that is, the use of peer to peer networking isn't illegal, although it is commonly used for piracy. otherwise, bittorrent is legal.