Teoría Flashcards
Protocol layering, packet switching, routing and data
streaming are the principles on which:
Computer Networks are based
The computers and other devices that use the network for
communication proposes are referred to as:
Host
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
This term is used to refer to any computer or switching
device attached to a network
Node
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 form 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
Wide Area Networks (WAN)
The end-to-end communication must provide totally errorfree; the detection of communication errors and their
correction is what we call:
Reliability
This is a sequence of binary data (an array of bits or bytes) of
restricted length, together with addressing information
sufficient to identify the source and destination of
computers
The simples form of packet
This is a unit of routing (delivering data from one part of the
internet to another)
Subnet
This is a 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 up to 50 kilometers.
Metropolitan Area Networks
(MANs)
This is defined as the ability to meet deadlines when
transmitting and processing streams of real-time multimedia
data.
Quality of service
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 the interconnection
Internetworks
This is why many network technologies support the
simultaneous transmission of messages to several recipients
Multicasting
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.
Wireless Metropolitan Area
Networks (WMANs)
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
They are composed of a number of personal devices such as
mobile phones, tablets, digital cameras, music players and so
on that are now carried by many people.
Wireless personal area networks
(WPANs)
They are generally used to hold the video frames, but
because the flow is continuous as opposed to the
intermittent traffic generated by typical client-server
interactions and are handled somewhat differently
UDP internet packets
In this type of network, most mobile phone networks are
based on digital wireless network technologies such as the
GSM standard, which is used in most countries of the world
Wireless wide area networks
(WWANs)
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
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.
Broadcasting
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 transmit it on outgoing circuit, which transfers
the packet to another node that is closer to its ultimate
destination.
Packet switching
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 automatic switch at the
exchange to the pir of wires connected to the other party´s
phone
Circuit switching
This is used to refer to a well-know set of rules and formats
to be used for communication between processes in order to
perform a given task
The term protocol
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
They are software-defined destinations points at a host
computer. They are attached to a processes, enabling data
transmission to be addressed to a specific process at a
destination node.
Ports
This is a numeric identifier that uniquely identifies a host
computer and enables it to be located by nodes that are
responsible for routing data to it.
A network address
When a pair of nodes connected to two separate networks
need to communicate through another type of network or
over an alien protocol, they can do so by constructing a
protocol under a scheme of:
Tunneling
This is a function that is required in all networks except
those LANs, such as the Ethernet, that provide direct
connections between all pairs of attached hosts.
Routing
A unified addressing scheme between different networks
that enables packets to be addressed to any host connected
to any subnet is a necessary element to build:
Internetwork
This must lend itself to the development of a flexible and
efficient routing scheme, but the addresses themselves
cannot contain very much of the information needed to
route a packet to its destination.
Addressing scheme
t is a based upon the permanent allocation of a normal IP
address to each mobile host on a subnet in its home domain
Mobile IP
The purpose of this is to monitor and control all
communication into and out of a intranet.
A Firewall
Message passing between a pair of processes can be
supported by two message communication operations
Send and receive operations
In this form of communication, the use of the send
operation is non-blocking, receive operation can have
blocking and non-blocking variants
The asynchronous form of
communication
We can describe this as the guaranteed to deliver the
message despite a reasonable number of packets being
dropped or lost
Reliability
Both forms of communication (UDP and TCP) use ______,
which provides an endpoint for communication between
processes
The socket abstaction
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
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:
Message destination
This consist of transmitting a message between a socket in
one process and a socket in another process
Interprocess communication
This is sent by UDP is transmitted from a sending process to
a receive process without acknowledgment or retries
A datagram
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 defines reliable communication for channels in terms of
two properties: integrity and validity
Failure Model
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 assume that when a pair of processes are establishing 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 scheme. If the
sender does not receive an acknowledgement with a time
out, it retransmit the message and this performed when:
Lost messages
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 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 Unmarshalling
They are three alternative approaches to external data
representation
XML, CORBA and Java´s object
serialization
The first one was designed for defining the appearance of
web pages while the second one was designed for writing
structured documents for the web.
HTML and XML
They are tagged with ‘markup’ strings. The tags are used to
describe the logical structure of the data and to associate
attribute-value pairs with logical structures.
XML data items
XML is _____ in the sense that users can define their own
tags, in contrast to HTML, which uses a fixed set of tags
Extensible
This is a markup language that was defined by the World
Wide Web Consortium (W3C) for general use on the web
XML
The structure of an XML document is defined by pairs of
these elements enclosed in angle brackets
Tags
They define the name of values associate to tags in XML
schemes
XML Attributes
This is used to enable clients to communicate with web
services and for defining the interfaces and other properties
of web services
XML Service
All the information in XML elements must be expressed as
character data.
But the question is: how do we represent encrypted
elements or secures hashes?
Binary data
Every start tag has matched end tag and all tags are correctly
nested, these are
Basic rules of XML
Every XML document must have this as its first line and must
at least specify the version of XML in use (chich is currently
1.0)
Prolog
This is a set of names for a collection of element types and
attributes that is referenced by a URL
XML Namespace
This defines the elements and attributes that can appear in a
document, how the elements are nested and the order and
number of elements, and whether an element is empty or
can include text
XML Schema
This protocol is based on a trio of communication primitives:
doOperation, getRequested and sendReplay
The request-reply protocol
This scheme involves the management of messages and
requires that each message have a unique element by which
it may be referenced
Messages identifiers
As its name indicates. It is a mechanism to call a procedure
or a function available on a remote computer
RPC
This uses the HTTP protocol to pass information from a
client computer to a server computer and uses a small XML
vocabulary to describe the nature of requests and responses
XML RPC
This specifies a procedure name and parameters in the XML
request, and the server returns either a fault or a response
in the XML response
XML-RPC client
Data model, request structures and response structures are
parts of
XML RPC Structure
There are a simple list of types and content – structs and
arrays are the most complex types available
XML RPC parameters
