SYSTEM MODELS

commonly used forms network interconnections. Client-server and peer-to-peer are two of the most elements being individual computers or aggregates of them supported by appropriate communication tasks performed by its computational elements; the computational Architectural models describe a system in terms of the computational and and their interconnectivity, without details of specific technologies.
Physical models consider the types of computers and devices that constitute a system which the design of distributed systems can usefully be described and discussed:
This chapter provides an explanation of three important and complementary ways inofarchitectural model for distributed systems.
Fundamental models take an abstract perspective in order to describe solutions to individual issues faced by most distributed systems.
There is no global time in a distributed system, so the clocks on different computers do not necessarily give the same time as one another. All communication between processes is achieved by means of messages. Message communication over a computer network
can be affected by delays, can suffer from a variety of failures and is vulnerable to security attacks. These issues are addressed by three models:
• The interaction model deals with performance and with the difficulty of setting time limits in a distributed system, for example for message delivery.
• The failure model attempts to give a precise specification of the faults that can be exhibited by processes and communication channels. It defines reliable communication and correct processes.
• The security model discusses the possible threats to processes and communication channels. It introduces the concept of a secure channel, which is secure against those threats.
 

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