Network and Web Technologies- S5 Flashcards
Internet
is a network of networks set up to allow computers to communicate with each other globally, using the same protocol.
The World Wide Web (WWW)
is a collection of web pages that resides on computers connected to the Internet.
Internet Service Providers
distributes internet connection to smaller providers who provide it to individual homes.
Uniform Resource Locators(URLs)
the full address of an Internet source.
Internet Registrars
Companies that hold records of all existing website names and the details of all the domain names that are available to purchase.
Internet Registries
Five global organisations with databases that hold records of all the domain names that have been issued and the details. The registries allocate IP addresses to the Domain name.
Domain Names
identifies the area that an internet resource resides in
Domain Name System(DNS)
a hierarchical decentralized naming system for computers, services, or other resources connected to the Internet or a private network. It catalogues all domain names and has a table corresponding domain names to IP addresses
Fully Qualified Domain Name (FQDN)
www.websitename.co.uk
Why do domain names sometimes have more than one IP address?
because if millions of people are requesting the same page, one computer/IP address could not process all of the requests.
What happens when the a URL is searched for in a web broweser
Web Page is requested using URL a user enters
The browser requests the corresponding IP address from a local DNS
If the DNS doesn’t have it, it goes up the hierarchy to a larger DNS database
When the IP address is located a data request is sent by the user’s computer to the location for the web page data.
Internet Protocol (IP addresses)
A unique address that is assigned to a network device.
Wide Area Networks (WANs)
are distributed around different regions and can connect to multiple LANs. Also uses packet switching.
Local Area Networks (LANs)
Is small and local consisting of a number of computing devices on a single site, connected by cables. Users on the network can communicate with each other and share data and hardware devices like printers.
Physical Bus Topology(Bus network)
in a LAN each node is connected to a main cable.
What are the pros and cons of a Bus network
Pro:- Less cable so cheaper
Con:- main cable fail=network data cannot be transmitted to any of the nodes.
-Performance degrades with heavy traffic because collision of data. Data then has to be sent again after a random time has passed.
-Low security (all computers on network can see all data being transmitted).
Physical Star Topology
Has a central node (switch, computer) which acts as a router to transmit messages.The switch keeps record of the MAC address of each device on the network so it can identify where to send the data too.
What are the pros and cons of a Star network
Pro:-If one cable fails, only one station is affected
-Performance stays the same when network heavily used
-Higher transmission feel=better performance
-No collisions (own cable)
-Secure (sent direct)
-Easy to add new station
Con:-Costly to install because of length of cables.
-If central device goes down, data can not be transmitted to nodes.
Physical topology
how the network is interconnected with wires and cables.
Logical topology
the communication mechanism for all nodes in a network and how they communicate across physical topology.
Wi-fi
a local area wireless technology that enables you to connect a device such as a PC to a network resource
Circuit switching
creates a direct link between two devices for the duration of the communication.
What are the pros and cons of circuit switching
Con: - bandwidth is wasted not alway is use
-two devices must send and receive at same rate
-Switched used to connect and disconnect circuits, electrical interference= may corrupt or lose data
Pro: packets arrive at same order so easier to put the message back together.
Packet switching
Splits data into packets and send the data across a network. There can be multiple transmission at different frequencies meaning the bandwidth is in constant use
Whats contained in Packet Switching
The header included the sender’s and the recipient’s IP addresses, the protocol being used, the packet number and a Time to Live (TTL) or hop limit, e.g an expiry date.
The payload contains the data being sent. And a checksum
Routers
used to connect to another network, traversing between them is called a hop.
Gateways
Going from one network to another network with a different protocol requires a gateway. The header data is stripped from the packet leaving only raw data, then new data is added in the format of the new network before the gateway sends the packet on its way.
Media Access Control (MAC) addresses
Every computer device has NIC which has has its own MAC address which uniquely identifies the device.
Protocol
a set of rules defining common methods of data communication. These rules need to be standard across all devices in order for them to communicate to each other.
What does the Application Layer do?
Uses protocols relating to the application being used to transmit data over network, usually the Internet
What does the Transport Layer do?
The data is split into packets and given a packet number. It is given a port number telling it which route to use.
The Network Layer
Adds the source and destination IP addresses. Routers use IP addresses to forward the packets to their destination.
The Link Layer
The physical connection between network nodes. Its puts the MAC address which allows the packet to identify the NICs of the source.
HTTP
HyperText Transfer Protocol, used for requesting a webpage on a browser
HTTPS
HyperText Transfer Protocol Secure, used requesting a webpage on a browser but securely
TCP/IP
Transmission Control Protocol/Internet Protocol. The basic communication language or protocol of the Internet. It can also be used as a communications protocol in a private networ
POP3
Post Office Protocol 3, Standard protocol for receiving protocol
SMTP
Simple Mail Transfer Protocol, A TCP/IP protocol used in sending and receiving e-mail.
IMAP
Internet Message Access Protocol, stores email messages on a mail server, but allows the end user to view and manipulate the messages as though they were stored locally on the end user’s computing device(s)
id=name
gives and identification, put within an attribute
HTML
a language used for creating web pages and web applications. The code describes the content and structure of a web page.
CSS
a scripting language similar to HTML that is used to describe the layout and styles of a web page. (describes how HTML elements are to be displayed on screen, paper, or in other media).
Three ways CSS can be implemented
In line, Internal/Embedded and external
Where is embedded/internal written
In the head and within style attributes
Where is Inline written
Inside the first (open) attribute of what you want to affect and use syle=””
Where is External written
An external sheet is written and a link attribute is used in the head. The link has rel=”stylesheet” href=”styles.css”. And no closing attribute only open
What is color:red called
A decleration
title1
This is an identification in CSS, therefore the corresponding rules only effect elements with that id name
p.centre
In CSS any tag with a class=”centre” will be effected
What is the Cascading order
In line has first priority. Then internal or external depending on which is written last. Then browser default
What is Red in hexadecimal
FF0000
What is Blue in hexadecimal
0000FF
What is Green in hexadecimal
00FF00
What is orange in hex
FFA500
What is yellow in hex
FFFF00
What is cyan in hex
00FFFF
Give a properties regarding background
background-color
Give three properties regarding Border
Border-style, Border-Width, Border-color
Give some values for Border-style
dotted, dashed, double, groove, ridge, Inset, Outset, none, hidden
Give a value for font-family
“New Times Roman”
Give values for font-style
normal, Italics and Oblique
JavaScript
programs the behaviour of the web page
Client-server networking
One or more computers are known as clients and are connected to a powerful central computer (the server). The client is dependent on the server to provide and manage the information, and all data is stored on the server. In a large network there may be many servers, each performing different tasks.
Give Pros and cons of Client-server networking
Pro: - security is better access to the central location are managed by the server.(user name and password)
-Individuals users don’t have to backup their data as it’s done centrally
-Data and other resources can be shared
-Clients are cheap therefore, good for big business
Con: - Expensive to install and manage
-Personal staff needed to maintain servers and run the network
Peer-peer networks
no central server, individual computers are connected to each other by LAN or WAN and act as a server and provide data.
Pros and Cons of peer-peer networks
Pro: - cheap to set up
- enables a share of resources like printer or router
-not difficult to maintain
-client doesn’t depend on the server
Con: -If machines on the network are slow they will slow down other machines.
-Each computer has to be backed up. Data can easily be deleted by users.
-No security