Web services are a new breed of Web application. They are self-contained, self-describing, modular applications thay can be published, located, and invoked across the web. Web services perform functions, which can be anything from simple requests to complicated business processes … Once a web service is deployed, other applications (and other web services) can discover and invoke the deployed service
IBM Web Service Tutorial
A distributed system is a collection of independent computers that appear to the user as a single coherent system, this is in contrast to a networked system. In a networked system computers exchange information, however in a distributed system an application has many parts running on different computiers, and information is shared to accomplish a specific purpose.
Distributed Systems allow resources to be more easily shared, to be location independant, to distribute human resources, to increase performance, to increase modularity and scalability and to increase availability and reliability.
Network Security is concerned with three main areas:
Multicast routing is the technique of sending a message to groups of end-points on a network in a one-to-many distribution. Generally the term multicast refers to IP multicasting, a method often used in media streaming systems as it can scale to a large number of recievers by not knowing details of individual recievers. It provides more efficient data distribution by not replicating packets to send them to multiple recievers.
A computer network protocol definies a format and order of messages sent and recieved among network entities, and actions taken on message transmission and reciept.
In a peer to peer (P2P) network every machine can communicate directly with every other machine in a network. No computers have any more authority than others. This is in direct contrast to client-server architecture.
A peer-to-peer (or P2P) computer network uses diverse connectivity between participants in a network and the cumulative bandwidth of network participants rather than conventional centralized resources where a relatively low number of servers provide the core value to a service or application.