DSYS - DISTRIBUTED SYSTEMS INTRO TEST
QUESTIONS AND ANSWERS
What are the most common problems in distributed systems? - ANSWER -
Time
What are the characteristics of distributed systems? - ANSWER - Multiple
processes: The system consists of more than one sequential process. These
processes can be either system or user processes, but each process should have
an independent thread of control—either explicit or implicit.
- Interprocess communication: Processes communicate with one another using
messages that take a finite time to travel from one process to another. The actual
nature or order of the delay will depend on the physical characteristics of the
message links. These message links are also called channels.
- Disjoint address spaces: Processes have disjoint address spaces. We will thus
not take into account a shared-memory multiprocessor as a true representation
of a distributed computing system. Note that programmers often represent
interprocess communication using shared-memory primitives, but the
abstraction of shared memory can be implemented using messages.
- Collective goal: Processes must interact with one another to meet a common
goal. Consider two processes P and Q in a network of processes. If P computes
f(x) = x^2 for a given set of values of x, and Q multiplies a set of numbers by π,
then we hesitate to call (P, Q) a distributed system, since there is no interaction
between P and Q. However, if P and Q cooperate with one another to compute
the areas of a set of circles of radius x, then (P, Q) collectively represent a
meaningful distributed system. Similarly, if a set of sellers advertise the cost of
their products, and a set of buyers post the list of the goods that they are
interested in buying as well as the prices they are willing to pay, then
individually, neither the buyers nor the sellers are meaningful distributed
systems, but when they are coupled into an auction system through the Internet,
then it becomes a meaningful distributed system.
, What is the reason for growing of the importance of distributed systems? -
ANSWER - Geographically distributed environment: First, in many situations,
the computing environment itself is geographically distributed. As an example,
consider a banking network. Each bank is supposed to maintain the accounts of
its customers. In addition, banks communicate with one another to monitor
interbank transactions or record fund transfers from geographically dispersed
automated teller machines (ATMs). Another common example of a
geographically distributed computing environment is the Internet, which has
deeply influenced our way of life. The mobility of the users has added a new
dimension to the geographic distribution.
- Speed up: Second, there is the need for speeding up computation. The speed of
computation in traditional uniprocessors is fast approaching the physical limit.
While multicore, superscalar, and very large instruction word (VLIW)
processors stretch the limit by introducing parallelism at the architectural level,
the techniques do not scale well beyond a certain level. An alternative technique
of deriving more computational power is to use multiple processors. Dividing a
total problem into smaller subproblems and assigning these subproblems to
separate physical processors that can operate concurrently are potentially an
attractive method of enhancing the speed of computation. Moreover, this
approach promotes better scalability, where the users or administrators can
incrementally increase the computational power by purchasing additional
processing elements or resources. This concept is extensively used by the social
networking sites for the concurrent upload and download of the photos and
videos of millions of customers.
- Resource sharing: Third, there is a need for resource sharing. Here, the term
resource represents both hardware and software resources. The user of computer
A may want to use a
What are some of the important issues in the study of the computational models
of distributed systems? - ANSWER - Knowledge of a process: The knowledge
of a process is local. No process is ordinarily expected to have global
knowledge about either the network topology or the global state. Each process
thus has a myopic view of the system. It is fair to expect that a process knows
(1) its own identity, (2) its own state, and (3) the identity of its immediate
neighbors. In some special cases, a process may also have exact or approximate
knowledge about the size (i.e., the number of nodes) of the network. Any other
QUESTIONS AND ANSWERS
What are the most common problems in distributed systems? - ANSWER -
Time
What are the characteristics of distributed systems? - ANSWER - Multiple
processes: The system consists of more than one sequential process. These
processes can be either system or user processes, but each process should have
an independent thread of control—either explicit or implicit.
- Interprocess communication: Processes communicate with one another using
messages that take a finite time to travel from one process to another. The actual
nature or order of the delay will depend on the physical characteristics of the
message links. These message links are also called channels.
- Disjoint address spaces: Processes have disjoint address spaces. We will thus
not take into account a shared-memory multiprocessor as a true representation
of a distributed computing system. Note that programmers often represent
interprocess communication using shared-memory primitives, but the
abstraction of shared memory can be implemented using messages.
- Collective goal: Processes must interact with one another to meet a common
goal. Consider two processes P and Q in a network of processes. If P computes
f(x) = x^2 for a given set of values of x, and Q multiplies a set of numbers by π,
then we hesitate to call (P, Q) a distributed system, since there is no interaction
between P and Q. However, if P and Q cooperate with one another to compute
the areas of a set of circles of radius x, then (P, Q) collectively represent a
meaningful distributed system. Similarly, if a set of sellers advertise the cost of
their products, and a set of buyers post the list of the goods that they are
interested in buying as well as the prices they are willing to pay, then
individually, neither the buyers nor the sellers are meaningful distributed
systems, but when they are coupled into an auction system through the Internet,
then it becomes a meaningful distributed system.
, What is the reason for growing of the importance of distributed systems? -
ANSWER - Geographically distributed environment: First, in many situations,
the computing environment itself is geographically distributed. As an example,
consider a banking network. Each bank is supposed to maintain the accounts of
its customers. In addition, banks communicate with one another to monitor
interbank transactions or record fund transfers from geographically dispersed
automated teller machines (ATMs). Another common example of a
geographically distributed computing environment is the Internet, which has
deeply influenced our way of life. The mobility of the users has added a new
dimension to the geographic distribution.
- Speed up: Second, there is the need for speeding up computation. The speed of
computation in traditional uniprocessors is fast approaching the physical limit.
While multicore, superscalar, and very large instruction word (VLIW)
processors stretch the limit by introducing parallelism at the architectural level,
the techniques do not scale well beyond a certain level. An alternative technique
of deriving more computational power is to use multiple processors. Dividing a
total problem into smaller subproblems and assigning these subproblems to
separate physical processors that can operate concurrently are potentially an
attractive method of enhancing the speed of computation. Moreover, this
approach promotes better scalability, where the users or administrators can
incrementally increase the computational power by purchasing additional
processing elements or resources. This concept is extensively used by the social
networking sites for the concurrent upload and download of the photos and
videos of millions of customers.
- Resource sharing: Third, there is a need for resource sharing. Here, the term
resource represents both hardware and software resources. The user of computer
A may want to use a
What are some of the important issues in the study of the computational models
of distributed systems? - ANSWER - Knowledge of a process: The knowledge
of a process is local. No process is ordinarily expected to have global
knowledge about either the network topology or the global state. Each process
thus has a myopic view of the system. It is fair to expect that a process knows
(1) its own identity, (2) its own state, and (3) the identity of its immediate
neighbors. In some special cases, a process may also have exact or approximate
knowledge about the size (i.e., the number of nodes) of the network. Any other
