Web Technology and Multimedia
The Internet
The internet is a worldwide communication system linking computers in geographically separate locations. It uses a variety of telecommunications links including local area networks, telephone lines, satellites and wireless. It enables fast communication between computers and the transfer of data between these. Both messages and data get passed from a source to a destination computer via other devices
Any computer can be linked to any other computer attached to the internet by sending data via intermediate computer systems
This is only achievable thanks to, common technical standards, a common identification system for computers and a common reference system for data files
World Wide Web (WWW)
WWW is the name given to the collection of information available to computers connected to the internet, and which is therefore available for anyone to access. The information is made up of web pages structured into websites. Websites are often interactive, allowing users to supply information to the server or to customise the web pages they are viewing- a concept originally described as Web 2.0
The term WWW is a standard way to refer to data anywhere on the internet
it is the collection of information that has grown up ion computers connected to the internet and has been made available for anyone to access by 'Surfing'
the WWW is organised into websites, which comprises several web pages and other types of file linked in to those web pages
URL- Uniform Resource Locator
URL, also known as URI (Uniform Resource Indicator) is the recognised method for referring to resources on the internet. Each resource, which is usually a file, has a reference
this is the recognised method of referring to resources on the internet
URLs are converted into IP addresses before being used to send requests to web servers
Each URL is a unique address that identifies each resource on the internet
In order the components of a URL are, the protocol for accessing the resource, the server on which the resource is stored, the domain name and the filename with any extension required
HTTP
HTTP is a protocol that defines the process of, identifying, requesting, transferring multimedia web pages across the internet
Such web pages are built using HTML
A secure variant, HTTPS, also exists
IP Addresses
IP= Internet Protocol
An IP address uniquely identifies the physical computer linked to the internet
A domain name server (DNS) converts a human-friendly domain name into its corresponding IP address
Static IP addresses do not change, and are used to address computers that are connected to the internet at all time
Dynamic IP addresses are assigned to computers that access the internet via an ISP when they log in, and thus the IP address may vary upon subsequent log ins
An IPv4 address is a unique number assigned to each computer connected to the internet
An IPv4 address consists of 2 parts, one identifying the network and one identifying the node (or host)
An IPv4 address consists of four numbers separated by full stops
the computer processes this as a 32-bit-pattern/four octets
it consists of 32 bits because each number can be represented as a byte(8 bits) and there are 4 of them
The smallest number s 0 and the largest is 255. the use of the number range of 0-255 is not a coincidence, it stems from the sue of binary in computing
ISPs buy the rights to use large volumes of IP addresses (that are not already reserved for internal use and resell these rights to the customers
you get 1 IP address per household, which is usually dynamic
Static IP addresses cost extra
Routers use IP addresses to identify devices that are allowed to read packets
Devices that aren't addressed in the header of a packet will not be able t open the data
IP addresses. This represents a standard set of rules used to ensure the proper transfer of information between computers on the internet. they define how data is to be structured and what control signals are used
every device linked to a network using the TCP/IP protocol is identified by a unique IP address
the IP address allows messages and data to be routed to the correct address on the network
each IP address maps onto a Fully Qualified Domain Name (FQDN)