JXTA

This talk presents a quick overview of JXTA. It is based on:

Li Gong. JXTA: A Network Programming Environment. [1] IEEE Internet Computing, (5)3, pp. 88-95, 2001.

Distributed object technologies like RMI, CORBA, DCOM, and SOAP assume a client\server architecture.
That is, applications written for them usually assume:
- Servers are well-known, always available, faster.
- Clients only want to communicate with servers.
- Clients are slower, less powerful, more likely to be residing in a workstation.
P2P applications such as distributed.net [2] and the many file-sharing systems have shown that this is not enough.
JXTA ("juxta") was designed to enable the implementation of sophisticated P2P application. That is, beyond file-sharing.
It was started as a SUN project, headed by Bill Joy, but then became open source. You can learn more by visiting the JXTA homepage [3].

Interoperability: Enable peers to easily find and communicate with each other, participating in community activities. It enables many different activities.
Platform independence: It will be independent of programming language, platform, or networking technology.
Ubiquity: It is designed to be implemented on every device, from PDA to mainframes.

Each peer is given a 128-bit unique identifier (UUID). These are not guaranteed to be globally unique.
Advertisements are XML documents that describe the existence of peers, peer groups, pipes, or services.
A peer is an entity that can understand all the required protocols.
Messages are the basic unit of communication. They should operate on asynchronous, unreliable, uni-directional transport. Messages contain an envelope and a body.
A peer group is a virtual entity that speaks the set of peer group protocols. There are no membership requirements. The World Peer Group includes everyone.
Pipes are communication channels for sending and receiving messages. They are unidirectional and asynchronous. Their endpoints can be moved among peers.
- A point-to-point pipe connects exactly two peers, sender and receiver.
- A propagate pipe connects multiple peer endpoints together.

Peer Discovery: Enables peers to find advertisements on other peers and can be used to find any of the peer, peer groups, or advertisements.
Peer Resolver: Enables a peer to send and receive generic search queries.
Peer Information: Allows a peer to learn about the capabilities and status of other peers.
Peer Membership: Allows a peer to get membership requirements, and to apply for, update, or cancel memberships.
Pipe Binding: Allows a peer to bind a pipe advertisement to a pipe endpoint, thus indicating where messages actually go over the pipe.
Endpoint routing: Allows a peer to ask a peer router for available routes for sending a message to a destination peer.

The 1.0 version provides some minimal security tools.
A simple crypto library with hash, symmetric (RC4), and asymmetric (RSA) algorithms.
An authentications framework modeled after PAM.
A password-based login scheme, to be used with above.
An access-control mechanism based on peer groups. Members share everything.
A transport mechanism bases on SSL/TLS.

JXTA is still being developed.
There are many interesting developments around it (e.g., the Poblano distributed trust model).
A good way to get started is by following this JXTA shell tutorial [4].

1 Peer-to-Peer