Parcial 1

Question 1

It is a main motivation for constructing distributed systems

Answer 1

The sharing of resources

Question 2

When all computer systems can fail and the responsability 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 their actions only by passing messages

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 the system to handle shares 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 computational 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 configures 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 stored of recently used data objects that is closer than the objects themselves

Answer 19

Proxy servers and caches

Question 20

This term referrers 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 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 of 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 failure.

Question 32

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 32

The enemy in the security model

Question 33

In this, we talk about the secutity 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 33

The security model

Question 34

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

Answer 34

Secure channels

Question 35

In this form of communication, the sending and receiving processes synchronize at every message. In this case, both send and receive are blocking operations

Answer 35

The synchronous communication

Question 36

In this form of communication, the use of the send operation is non-blocking, the receive operation can have blocking and non-blocking variants

Answer 36

The asynchronous communication

Question 37

We can describe this as the guarantee to deliver the message despite a reasonable number of packets being dropped or lost.

Answer 37

Reliability

Question 38

This consist of transmitting a message between a socket in one process and a socket in another process.

Answer 38

Inter-process communication

Question 39

Any process may make use of multiple of these elements to receive messages, but a process cannot share them with other processes on the same computer

Answer 39

Ports

Question 40

The internet protocols and the local port pairs define the:

Answer 40

The message destination

Question 41

Both forms of communications (UDP and TCP) use ________ which provides and endpoint for communication between processes

Answer 41

The socket abstraction

Question 42

This is sent by UDP is transmitted from a sending process to a receive process without acknowledgement or retries

Answer 42

A datagram

Question 43

Message passing between a pair of processes can be supported by two message communication operations

Answer 43

Send and receive operations

Question 44

Messages may be dropped occasionally, either because of a checksum error or because no buffer space is available at the source or destination, it's called:

Answer 44

Omission failures

Question 45

This assume that when a pair of processes are stablishing a connection, one of them plays the client role and another plays the server role, but thereafter they could be peers.

Answer 45

The API for stream communication

Question 46

The TCP protocol uses an acknowledgement sheme. If the sender does not receive and acknowledgement with a time out, it retransmits the message and this is performed when:

Answer 46

There is lost messages

Question 47

This defines reliable communication for channels in terms of two properties: integrity and validity

Answer 47

A failure model

Question 48

They are three alternatives approaches to external data representation.

Answer 48

XML, CORBA and Java's object serialization.

Question 49

This was originated from BSD 4.x UNIX and provides the abstraction of a stream of bytes to which data may be written and from which data may be read

Answer 49

The API to the TCP protocol.

Question 50

This is the process of taking a collection of data items and assembling or disassembling (respectively) into a form suitable for transmission in a message

Answer 50

Marshalling and un-marshalling

Question 51

The TCP protocol attempts to match the speeds of the processes that read from and write to a stream, this is called:

Answer 51

Flow control

Question 52

These items transmitted in messages can be data values of many different types, and not all computers store primitive values such as integers in the same order

Answer 52

The individual primitive data

Question 53

This is a markup language that was defined by the World Wide Web Consortium (W3C) for general use on the Web

Answer 53

XML

Question 54

This is the speed at which data can be transferred between two computers in the network once transmission has begun

Answer 54

Data transfer rate

Question 55

This is a single communication subsystem providing communication between all of the hosts that are connected to it, where the Internet is constructed from many subnets

Answer 55

The Internet

Question 56

They carry messages at lower speeds between nodes that are often in different organizations and may be separated by large distances

Answer 56

WANs

Question 57

Protocol layering, packet switching, Routing and data streaming are the principles on which:

Answer 57

Computer networks are based

Question 58

This term is used to refer to any computer or switching device attached to a network

Answer 58

Node

Question 59

This is a sequence of binary data (an array of bits and bytes) of restricted length, together with addressing information sufficient to identify the source and destination computers.

Answer 59

The simplest form of packet

Question 60

The end-to-end communication must provide totally error-free; the detection of communication errors and their correction is that we call:

Answer 60

Reliability

Question 61

This is the delay that occurs after a send operation is executed before data starts to arrive at the destination computer in network performance

Answer 61

Latency

Question 62

The computers and other devices that use the network for communication purposes are referred to as:

Answer 62

Host

Question 63

This is a communication subsystem in which several networks are linked together to provide common data communication facilities that overlay the technologies and protocols of the individual component networks and the methods used for their interconnection

Answer 63

An internetwork

Question 64

This is why many network technologies support the simultaneous transmission of messaged to several recipients

Answer 64

Multicasting

Question 65

This is a unit of routing (delivering data from one part of the internet to another)

Answer 65

A subnet

Question 66

They are generally used to hold the video frames, but because the flow is continous as opposited to the intermittent traffic generated by typical client-server interactions and are handled somewhat differently

Answer 66

UDP internet packets

Question 67

This is defined as the ability to meet deadlines when transmitting and processing streams of real-time multimedia data

Answer 67

Quality of service

Question 68

This type of network is based on the high bandwidth copper and fiber optic cabling recently installed in some towns and cities for the transmission of video, voice and other data over distances of up to 50 kilometers

Answer 68

MAN's

Question 69

They are composed of number of personal devices such as movile phones, tablets, digital cameras, music players and so on that are now carried by many people

Answer 69

WPAN's

Question 70

This is referred to as the transmission and display of audio and video in real time. It requires much higher bandwidths than most other forms of communication in distributed systems

Answer 70

Streaming

Question 71

The IEEE 802.16 WiMAX standard is targeted at this class of network. It aims to provide an alternative to wired connections to home and office buildings

Answer 71

WMAN's

Question 72

In this type of switching, each packet arriving at a node is first stored in memory at the node and then processed by a program that transmits it on an outgoing circuit, which transfers the packet to another node that is closer to its ultimate destination

Answer 72

Packet switching

Question 73

This is used to refer to a well-known set of rules and formats to be used for communication between processes in order to perform a given task

Answer 73

The term protocol

Question 74

Their operation was simple to understand, when a caller dialed a number, the pair of wires from her phone to the local exchange was connected by an automaticswitch at the exchange to the pair of wires connected to the other party's phone

Answer 74

Circuit Switching

Question 75

They are specifically designed to provide high bandwidth and low latencies and to support quality of service by the reservation of network resources.

Answer 75

ATM Networks

Question 76

Most mobile phone networks are based on digital wireless network technologies such as the GSM (Global System for Mobile communication) standard, which is used in most countries of the world.

Answer 76

WWANs

Question 77

This is a transmission technique that involves no switching, everything is transmitted to every node, and it is up to potential receivers to notice transmissions addressed to them.

Answer 77

Broadcast

Question 78

The task of dividing messages into packets before transmission and reassembling them at the receiving computer is usually performed in the transport layer.

Answer 78

Packet assembly

Question 79

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

Answer 79

Process Omission Failure