1exam

Question 1

It is a main motivation for contructing distributed system

Answer 1

The sharing of resources

Question 2

When all computer systems can fail and the responsibility of system designers is to plan for the consequences of it, is called

Answer 2

Independent failures

Question 3

It is one in which components located at networked computers communicate and coordinate

Answer 3

A distributed systems

Question 4

They are three examples of distributed systems

Answer 4

Internet, Intranet, and ubiquitous computing

Question 5

It is the capacity of system to handle shared resources can be increased by adding more resources to the network

Answer 5

Concurrency

Question 6

Its role is to protect an intranet by preventing unauthorized messages leaving or entering

Answer 6

Firewall

Question 7

The portability of many of these devices, together with their ability to
connect conveniently to networks in different places, make this type of
computing possible.

Answer 7

Mobile computing

Question 8

It is the harnessing of many small, cheap computacional devices that are
present in user physical environments, including the home, office and
elsewhere.

Answer 8

Ubiquitous computing

Question 9

It is a portion of the Internet that is separately administered and has a
boundary that can be configured to enforce local security polices.

Answer 9

An intranet

Question 10

It is a vast interconnected collection of computer networks of many
different types, programs running on the computers connected to it
interact by passing messages, employing a common means of
communication.

Answer 10

The internet

Question 11

They are three of the challenges in
distributed systems that must be meet by
designers to be aware of them are:

Answer 11

Heterogeneity, Openness and Scalability

Question 12

The Web is based on three main standard
technological components:

Answer 12

HTML, URL, and the client-server system architecture

Question 13

They are transparencies that must meet
the distributed systems.

Answer 13

Location, failure and performance.

Question 14

This challenge is defined as the
concealment from the user and the
application programmer of the separation
of components in a distributed system, so
that the system is perceived as a whole
rather than as a collection of independent
components

Answer 14

Transparency

Question 15

In this challenge both services and
applications provide resources that can be
shared by clients in a distributed systems.

Answer 15

Concurrency

Question 16

This is the lowest-layer which bring the system’s programming
interface up to a level that facilities communication and
coordination between processes.

Answer 16

System Platform

Question 17

It is concerned with the placement of a distributed system parts
and the relationships between them.

Answer 17

The architectural model of DS

Question 18

It is a layer of software whose purpose is to mask heterogeneity
and provide a convenient programming model to application
programmers.

Answer 18

Middleware

Question 19

In this architecture model, a cache is a store of recently used
data objects that is closer than the objects themselves.

Answer 19

Proxy servers and caches

Question 20

This term referres to the structuring of software as layers or
modules in a single computer and in terms of services offered
and requested between processes located in the same or
different computers

Answer 20

Software architecture design

Question 21

It is a running program that
travels from one computer to
another in a network carrying
out a task on someone’s
behalf, such as collecting
information, eventually
returning with the results.

Answer 21

A mobile agent

Question 22

This is the architecture model
that is most cited when
distributed systems are
discussed.

Answer 22

Client-Server model

Question 23

It is the form of distribution
that integrates mobile devices
and other devices into a given
network with easy connection,
easy integration, limited
connectivity, etc

Answer 23

Spontaneous networking

Question 24

Performance issues arising
from the limited processing
and communication capacities
of computers and networks are
considered under the following
subheadings:

Answer 24

Responsiveness, throughput and balancing computational loads.

Question 25

In this architecture all of the
processes play similar roles,
interacting cooperatively as
peers to perform a distributed
activity or computation
without any distinction
between clients and servers.

Answer 25

Peer processes

Question 26

Dependability issues is a requirement in most
application domains. We defined the dependability of
computer systems as:

Answer 26

Correctness, security and fault tolerance.

Question 27

This is performed when in many cases, we are
interested in knowing whether an event (sending or
receiving a message) at one process occurred before,
after concurrently with another event at another
process.

Answer 27

Event ordering

Question 28

In this type of Distributed System, the time to execute
each step pf a process has know lower and upper
bounds

Answer 28

Synchronous Distributed Systems

Question 29

Each computer in a distributed system has its own
internal clock, which can be used by local processes to
obtain the value of the current time. This concept
refers to the relative amount that a computer clock
differs from a perfect reference clock.

Answer 29

Clock drift rate

Question 30

In this type of Distributed System, process execution
speed, this is that each step may take an arbitrarily
long time.

Answer 30

Asynchronous Distributed Systems

Question 31

When it does not transport a message from p’s outgoing
message buffer to q’s incoming message buffer which is
known as ‘dropping message’ we are talking about:

Answer 31

Communication omission failures

Question 32

When we say that a process has crashed we mean that it has
halted and will no execute any further steps of its program
ever, this is a type of:

Answer 32

Process omission failure.

Question 33

To model security threats, we postulate that this element is
capable of sending any message to any process and reading
or copying any message between a pair of processes.

Answer 33

The enemy in the securoty model

Question 34

In this, we talk about the security of a distributed system that
can be achieved by securing the processes and the channels
used for their interactions and by protecting the objects that
they encapsulate against unauthorized access

Answer 34

The security model

Question 35

Encryption, authentication and Identification some times are
used to build __________ as a service layer on top of existing
communication services.

Answer 35

Secure channels