csci 387 quiz 5 Flashcards
benefits of distributed systems
- can be scaled to cope with increasing demand
- can continue to provide user services if parts of the system fail
- enable resources to be shared
issues to be considered in the design of distributed systems
transparency, openness, scalability, security, quality of service, failure management
client-server systems are structured into ?
layers
the presentation layer of client-server systems is implemented on
a client computer
client-server systems: servers provide
data management, application, and database services
client-server systems may have several tiers with ?
different layers of the system distributed to different computers
architectural patterns for distributed systems
master-slave, two-tier and multi-tier client-server, distributed component, and peer-to-peer
distributed component systems require middleware to ?
handle component communications and to allow components to be added to and removed from the system
peer-to-peer architectures are
decentralized with no distinguished clients and servers
in peer-to-peer architectures, computations can be
distributed over many systems in different organizations
software as a service is
a way of deploying applications as thin client-server systems, where the client is a web browser
distributed systems are (more/less) complex than systems that run on a single processor
more
the types of attack that a distributed system must defend itself against are
interception, interruption, modification, fabrication
two types of interaction between components in a distributed system
- procedural (one computer calls on a known service offered by another and waits for a response)
- message-based (the sending computer sends info about what is required to another computer - not necessary to wait for a response)`
in master-slave architecture, the ‘master’ process is usually responsible for
computation, coordination, and communications (controls the slave processes)
in master-slave architecture, the ‘slave’ processes are
dedicated to specific actions
in a two-tier client-server architecture, the system is implemented as
a single logical server plus an indefinite number of clients that use that server
thin-client model
the presentation layer is implemented on the client and all other layers are implemented on a server
fat-client model
some of all of the application processing is carried out on the client; data management and database functions are implemented on the server
disadvantage of thin-client model
places a heavy processing load on both the server and the network
the fat-client model is most suitable for
new systems where the capabilities of the client system are known in advance
disadvantage to the fat-client model
new versions of the application have to be installed on all clients
benefits of distributed component architecture
system designer can delay decisions on where/how services are provided, allows new resources to be added as required, flexible, scalable, possible to reconfigure the system dynamically
disadvantages of distributed component architecture
more complex to design, standardized middleware never been accepted
? are the principal reason by p2p architectures are not widely used because ?
security concerns; the lack of central management means that malicious nodes can be set up to deliver spam and malware to other nodes in the network
SaaS stands for ? and involves ?
Software as a Service; hosting the software remotely and providing access to it over the internet
