What are distributed systems?

• There are many definitions
• Basically: a number of computers or computing nodes that are linked by a network and that share data, processing or both (DeWire 1994)

Why distributed systems?

• Performance
• Scalability
• Resource sharing
• Elegance?

Why not distributed systems?

• Latency -communication overhead
• Synchronisation - how do independent processes share data and maintain integrity?
• Partial failure - a distributed system should continue to function even if parts of it are not available
• Additional complexity - distributed systems are much more complex than local ones

Scope of the unit

• Look at the different patterns for distributed systems
• Look at the additional issues for distributed systems versus stand-alone systems
• Using Java, cover the programming aspects of distibuted systems, including
  • sockets
  • remote procedure call
  • remote method invocation
  • peer to peer