DSYS - DISTRIBUTED SYSTEMS MODELS EXAM
QUESTIONS AND ANSWERS
What are the different types of basic distributed system models? - ANSWER
Physical Models
Architectural Models
Fundamental Models
What is a physical model? - ANSWER A representation of the underlying
hardware elements of a distributed system that abstracts from specific details of
the computer and networking technologies employed.
What is a baseline physical model - ANSWER • Hardware and software
components located at networked computers communicate and coordinate their
actions only by passing messages
•Very simple physical model of a distributed system
What are some examples of physical models? - ANSWER Baseline physical
model
Early distributed (LAN)
Internet-scale
Contemporary
What is the difference between the architectural model and fundamental model?
- ANSWER An architectural model is concerned with the placement of its
components and the relationships between them
‣client-server systems
‣peer-to-peer systems
Fundamental models are concerned with a more abstract description of the
properties that are common in all of the architectural models
What are the 4 building blocks of an architectural model? - ANSWER 1.
Communicating entities
2. Communication paradigms
3. Roles and responsibilities
4. Placement
, Communicating entities: what are the entities that are communicating in the
distributed system? (From a system-oriented perspective) - ANSWER
‣communicating entities are processes
‣distributed system: processes coupled with appropriate interprocess
communication paradigms
‣two caveats:
-In primitive environments such as sensor networks, operating systems does not
provide any abstractions, therefore nodes communicate
-in most distributed environments, processes are supplemented by threads
(lightweight processes), so, strictly speaking, it is threads that are endpoints of
communication
Communicating entities: what are the entities that are communicating in the
distributed system? (From a programming perspective) - ANSWER Objects
•Computation consists of a number of interacting objects representing units of
decomposition for the problem domain
•Objects are accessed via interfaces
Components
•Resemble objects in that they offer problem-oriented abstractions, also
accessed via interfaces
•Difference - Specify assumptions for their interfaces and also the assumptions
they make for other components/interfaces that must hold for their functions to
be fulfilled
Web services
•Software application which is identified via URI
•Supports direct interactions with other software agents
-Intrinsically integrated in the WWW, using web standards to represent and
discover services
Communication paradigms: how do these entities communicate, or, more
specifically, what communication paradigm is used? - ANSWER -Interprocess
communication
-Remote invocation
-Indirect communication
What is interprocess communication? - ANSWER •Low-level support for
communication between processes in distributed systems including message
parsing-primitives, socket programming, and multicast communication
QUESTIONS AND ANSWERS
What are the different types of basic distributed system models? - ANSWER
Physical Models
Architectural Models
Fundamental Models
What is a physical model? - ANSWER A representation of the underlying
hardware elements of a distributed system that abstracts from specific details of
the computer and networking technologies employed.
What is a baseline physical model - ANSWER • Hardware and software
components located at networked computers communicate and coordinate their
actions only by passing messages
•Very simple physical model of a distributed system
What are some examples of physical models? - ANSWER Baseline physical
model
Early distributed (LAN)
Internet-scale
Contemporary
What is the difference between the architectural model and fundamental model?
- ANSWER An architectural model is concerned with the placement of its
components and the relationships between them
‣client-server systems
‣peer-to-peer systems
Fundamental models are concerned with a more abstract description of the
properties that are common in all of the architectural models
What are the 4 building blocks of an architectural model? - ANSWER 1.
Communicating entities
2. Communication paradigms
3. Roles and responsibilities
4. Placement
, Communicating entities: what are the entities that are communicating in the
distributed system? (From a system-oriented perspective) - ANSWER
‣communicating entities are processes
‣distributed system: processes coupled with appropriate interprocess
communication paradigms
‣two caveats:
-In primitive environments such as sensor networks, operating systems does not
provide any abstractions, therefore nodes communicate
-in most distributed environments, processes are supplemented by threads
(lightweight processes), so, strictly speaking, it is threads that are endpoints of
communication
Communicating entities: what are the entities that are communicating in the
distributed system? (From a programming perspective) - ANSWER Objects
•Computation consists of a number of interacting objects representing units of
decomposition for the problem domain
•Objects are accessed via interfaces
Components
•Resemble objects in that they offer problem-oriented abstractions, also
accessed via interfaces
•Difference - Specify assumptions for their interfaces and also the assumptions
they make for other components/interfaces that must hold for their functions to
be fulfilled
Web services
•Software application which is identified via URI
•Supports direct interactions with other software agents
-Intrinsically integrated in the WWW, using web standards to represent and
discover services
Communication paradigms: how do these entities communicate, or, more
specifically, what communication paradigm is used? - ANSWER -Interprocess
communication
-Remote invocation
-Indirect communication
What is interprocess communication? - ANSWER •Low-level support for
communication between processes in distributed systems including message
parsing-primitives, socket programming, and multicast communication
