Parcial 1 Flashcards
Examen
It is a main motivation for constructing distributed systems
The sharing of resources
When all computer systems can fail and the responsability of system designers is to plan for the consequences of it, is called:
Independent failures
It is one in which components located at networked computers communicate and coordinate their actions only by passing messages
A distributed systems
They are three examples of distributed systems
Internet, Intranet and Ubiquitous computing
It is the capacity of the system to handle shares resources can be increased by adding more resources to the network
Concurrency
Its role is to protect an intranet by preventing unauthorized messages leaving or entering
Firewall
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
Mobile computing
It is the harnessing of many small, cheap computational devices that are present in user physical environments, including the home, office and elsewhere
Ubiquitous computing
It is a portion of the internet that is separately administered and has a boundary that can be configures to enforce local security polices
An intranet
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
The internet
They are three of the challenges in distributed systems that must be meet by designers to be aware of them are
Heterogeneity, Openness and Scalability
The Web is based on three main standard technological components:
HTML, URL and the Client-Server System Architecture
They are transparencies that must meet the distributed systems
Location, failure and performance
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.
Transparency
In this challenge both services and applications provide resources that can be shared by clients in a distributed systems
Concurrency
This is the lowest-layer which bring the system’s programming interface up to a level that facilities communication and coordination between processes
System Platform
It is concerned with the placement of a distributed system parts and the relationships between them
The architectural model of DS
It is a layer of software whose purpose is to mask heterogeneity and provide a convenient programming model to application programmers
Middleware
In this architecture model, a cache is stored of recently used data objects that is closer than the objects themselves
Proxy servers and caches
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
Software architecture design
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
A mobile agent
This is the architecture model that is most cited when distributed systems are discussed
Client-Server Model
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.
Spontaneous networking
Performance issues arising from the limited processing and communication capacities of computers and networks are considered under the following subheadings
Responsiveness, throughput and balancing computational loads
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
Peer processes
Dependability issues is a requirement in most application domains. We defined the dependability of computer systems as:
Correctness, security and fault tolerance.
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.
Event ordering
In this type of Distributed System, the time to execute each step of a process has know lower and upper bounds
Synchronous Distributed Systems
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.
Clock drift rate
In this type of Distributed System, process execution speed, this is that each step may take an arbitrarily long time.
Asynchronous Distributed Systems
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:
Communication omission failure.
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
The enemy in the security model
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
The security model
Encryption, authentication and Identification some times are used to build ———— as a service layer on top of existing communication services
Secure channels
In this form of communication, the sending and receiving processes synchronize at every message. In this case, both send and receive are blocking operations
The synchronous communication
In this form of communication, the use of the send operation is non-blocking, the receive operation can have blocking and non-blocking variants
The asynchronous communication
We can describe this as the guarantee to deliver the message despite a reasonable number of packets being dropped or lost.
Reliability
This consist of transmitting a message between a socket in one process and a socket in another process.
Inter-process communication
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
Ports
The internet protocols and the local port pairs define the:
The message destination
Both forms of communications (UDP and TCP) use ________ which provides and endpoint for communication between processes
The socket abstraction
This is sent by UDP is transmitted from a sending process to a receive process without acknowledgement or retries
A datagram
Message passing between a pair of processes can be supported by two message communication operations
Send and receive operations
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:
Omission failures
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.
The API for stream communication
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:
There is lost messages
This defines reliable communication for channels in terms of two properties: integrity and validity
A failure model
They are three alternatives approaches to external data representation.
XML, CORBA and Java’s object serialization.
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
The API to the TCP protocol.
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
Marshalling and un-marshalling
The TCP protocol attempts to match the speeds of the processes that read from and write to a stream, this is called:
Flow control
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
The individual primitive data
This is a markup language that was defined by the World Wide Web Consortium (W3C) for general use on the Web
XML
This is the speed at which data can be transferred between two computers in the network once transmission has begun
Data transfer rate
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
The Internet
They carry messages at lower speeds between nodes that are often in different organizations and may be separated by large distances
WANs
Protocol layering, packet switching, Routing and data streaming are the principles on which:
Computer networks are based
This term is used to refer to any computer or switching device attached to a network
Node
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.
The simplest form of packet
The end-to-end communication must provide totally error-free; the detection of communication errors and their correction is that we call:
Reliability
This is the delay that occurs after a send operation is executed before data starts to arrive at the destination computer in network performance
Latency
The computers and other devices that use the network for communication purposes are referred to as:
Host
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
An internetwork
This is why many network technologies support the simultaneous transmission of messaged to several recipients
Multicasting
This is a unit of routing (delivering data from one part of the internet to another)
A subnet
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
UDP internet packets
This is defined as the ability to meet deadlines when transmitting and processing streams of real-time multimedia data
Quality of service
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
MAN’s
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
WPAN’s
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
Streaming
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
WMAN’s
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
Packet switching
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
The term protocol
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
Circuit Switching
They are specifically designed to provide high
bandwidth and low latencies and to support quality of
service by the reservation of network resources.
ATM Networks
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.
WWANs
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.
Broadcast
The task of dividing messages into packets before transmission and reassembling them at the receiving computer is usually performed in the transport layer.
Packet assembly
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:
Process Omission Failure
