JXTA Overview

Objectives

• JXTA ("juxta") was designed to permit implementation of P2P applications using Java.

Characteristics

• Interoperability:  Enable peers to find and communicate with each other.
• Platform independence:  Independent of programming language, platform, network technology.
• Ubiquity:  designed to be implemented on every device (PDAs, servers, etc.).

Architecture

• Core:  manages communication and peer establishment.
• Middle:  handles services (indexing, searching, file sharing).

JXTA Objects and Details

• Each peer is given a 128-bit (not guaranteed to be globally) unique identifier.
• Advertisements:  XML documents describing existence of peers, peer groups, pipes, or services.
• Peer:  entity that understands all required protocols.
• Messages:  base unit of communication, composed of an envelope and a body.  Should operate on asynchronous, unreliable, uni-directional transport.
• Peer Group:  virtual entity that "speaks" the set of peer group protocols.  The World Peer Group includes all.
• Pipes:  communication channels for sending and receiving messages.  Unidirectional and asynchronous, their endpoints can be moved among peers.
  • Point-to-Point Pipe:  connects exactly two peers.
  • Propagate Pipe:  connects multiple peer endpoints.

Protocols

• Peer Discovery:  allows peers to find advertisements on other peers; used to find peers, peer groups, advertisements.
• Peer Resolver:  allows a peer to send and receive generic search queries.
• Peer Information:  allows a peer to learn capabilities and status of other peers.
• Peer Membership:  allows a peer to fetch membership requirements, and apply for, update, or cancel memberships.
• Pipe Binding:  allows a peer to bind a pipe advertisement to a pipe endpoint; indicates where messages actually go when traversing a pipe.
• Endpoint Routing:  allows a peer to query a peer router for available routes in order to send a message to a destination peer.

Discovery Mechanisms

• LAN-based:  broadcast.
• Peer can receive invitation message that tells about other peer.
• Peer A can query another peer B about the peers that B knows about.
• Rendezvous peer can act as source of information (directory) about peers.

Security

• Hash, symmetric (RC4) and assymetric (RSA) algorithms.
• PAM-like authentication framework.
• Password-based login scheme.
• Access control mechanism based on peer groups, where members share everything.
• Transport mechanism based on SSL/TLS.

Adapted from Jose M. Vidal (http://jmvidal.cse.sc.edu/talks/jxta/).