various resources of a computersystem must be protected againstdestruction and unauthorized access.
Enforcing security in a distributed system ismore difficult because of the lack of asingle point of control and the use ofinsecure networks for data communication
Reliability and fault tolerance
manages multiple resources, must bedesigned properly to increase the system'sreliability
higher reliability needed to avoid faults,tolerate faults and to detect andrecover from faults
Commonly used methods are faultavoidance and fault tolerance.
Openness
Determines whether the system can beextended in various ways withoutdisrupting existing system and services
should be flexible due: Ease ofmodification & Ease of enhancement
Heterogeneity
heterogeneous distributed system consistsof interconnected sets of dissimilarhardware or software systems
diversity causing heterogenousdistributed system far more difficult formhomogenous
heterogenous preferred as it provideflexibility
Performance & scalability
overall performance should be better thanor at least equal to that of running thesame application on a singleprocessorsystem
design principle should be consideredbatch, cache, minimize copying of data,minimize network traffic, take advantage offinegrain parallelism for multiprocessing
Communication
essential part of distributed systems e.g.,clients and servers must communicate forrequest and response
Synchronous or blocking senderwaits for receiver to execute a receiveoperation
Asynchronous or nonblocking
Transparency
no common clock among the multipleprocessors
difficult task and requires that severaldifferent aspects of transparency