Basic components of the Web

The basic components of the Web are:

• Web servers, which are computers that carry distribution information over the Internet. For the example, one Web server may contain the online magazine what‘s On in Bath's text and images, and another server may contain details on which seats are available for a specific concert. The magazine will use the Web's own publishing language, HTML (Hypertext Mark-up Language), to format. The data on the seating applicable and their prices will be kept in a database with links to different forms published using HTML.

• Servers that can also be PCs, Macintosh systems or workstations from UNIX: it is the server software that makes them different, not the machine itself. The servers must be relatively up-to-market devices. Servers must always be left running, so that people can access information about them whenever they prefer. Another significant thing about servers: they are comparatively hard to set up. If you're a non- technical person who wants to be published on the Internet, it's best to rent some room on someone else's site.

• Web clients that can be PCs, Macintoshes and other internet enabled devices that can access information from Web servers. The machine at your desk is a Web client. Server applications can be run by PCs, Macintoshes, UNIX workstations and even single terminals. Different lient software for various platforms is marketed .Thus Mosaic has both an implementation of Macintosh and a PC.

• HTTP protocol used for transmission of files between servers and clients. When you click on a hypertext link or fill out a form in a Web document, the results must be sent as quickly as possible over the Internet and then understood by a server at the other end. Instructions like 'give me this file' or 'get me the picture' are carried by the HTTP web communication protocol. This protocol is the 'messenger' that gathers files from and to servers, and then delivers results to your computer whenever you click on a button. Among other Internet services, HTTP has its counterparts: FTP, file transfer protocol, and Gopher are protocols which obtain different kinds of information from across the Internet.

• Browser software which a Web client requires to view text, pictures, video clips, etc. This is given under the generic name 'browser,' which is perhaps the best-known example of Internet Explorer by Mosaic, Microsoft Corp. and Netscape Communications Corp.'s Navigator and Communicator browsers. It gives the software ability to search Web server collected information, as you would browse through a book. It also provides you with facilities to save and print information accessed on the Internet.

Navigating the Web

There are three main ways to move between web pages or websites:

1. Clicking a text link.

2. Clicking a hyperlinked graphic, such as a button, photograph, or drawing.

3. Typing the URL of a web page in the location box (also known as the address field) of your web browser and then pressing the Enter or Return key.

Scheme specifiers

At the start of a web URI, the scheme specifiers http:/ and https:/ refer to the Hypertext Transfer Protocol or HTTP Stable, respectively. They specify the protocol of communication to be used for request and reply. The HTTP protocol is fundamental to the operation of the World Wide Web and when browsers send or retrieve sensitive data, such as passwords or banking information, the added encryption layer of HTTPS is vital. Web browsers normally prepend http:/ to user-entered URIs automatically, if omitted.

What is a URL?

URL is the abbreviation for Uniform Resource Locator and is known on the World Wide Web as the global address of documents and other resources. For instance, you'll go to the URL www.google.com to visit a website. A domain name is part of a URL, which stands for Uniform Resource Locator.

Computers rely on a language consisting of numbers and letters called an IP address, so that computer networks and servers can "speak to each other." Each computer connecting to the Internet has a unique IP address. Typing in a long IP address is not ideal, or practical, for an online user to navigate quickly across the Network. That's why domain names have been developed-to cover IP addresses with something more memorable. The domain name may be called a "nickname" to the IP address. A URL, along with other basic information, includes the domain name to create a complete address (or "web address") to guide a visitor to a particular online website called a webpage. Essentially it's a series of directions and every web page has a special one.

Domain Name System

DNS stands for Domain Name System. DNS 'principal role is to convert domain names into IP addresses that computers can recognize. This also lists mail servers that accept Emails for each domain name. Internet machine is assigned a unique address, which is called an IP address. So looks a standard IP address: 199.123.456.7

It's very hard to keep in mind the IP addresses of all the websites that we visit daily. Words are easier to remember than numeral strings. It's here that domain names get into the picture. What you need to know when you visit a website is their URL. Computers remember numbers, and DNS helps to translate the URL to an IP address that the machine can use. If you type domain.com into the user, the user wants to get the www.domain.com IP address first. The user contacts a DNS server to ask where the web pages are located. It acts as an IP address directory service.

DNS Servers and IP Addresses

There are billions of IP addresses currently in use, and most machines have a human-readable name as well. DNS servers (cumulatively) are processing billions of requests across the internet at any given time. Millions of people are adding and changing domain names and IP addresses each day.

With so much to handle, DNS servers rely on network efficiency and internet protocols. Part of the IP's effectiveness is that each machine on a network has a unique IP address in both the IPV4 and IPV6 standards managed by the Internet Assigned Numbers Authority (IANA). Here are some ways to recognize an IP address:

• An IP address in the IPV4 standard has four numbers separated by three decimals, as in: 70.74.251.42

• An IP address in the IPV6 standard has eight hexadecimal numbers (base-16) separated by colons, as in 2001:0cb8:85a3:0000:0000:8a2e:0370:7334.

• Each number in an IPV4 number is called an "octet" because it's a base10 equivalent of an 8-digit base-2 (binary) number used in routing network traffic. For example, the octet written as 42 stands for 00101010. Each digit in the binary number is the placeholder for a certain power of two from 2 to 27, reading from right to left. That means that in 00101010, you have one each of 21, 23 and 25. So, to get the base10 equivalent, just add 21 + 23 + 25 = 2 + 8 + 32 = 42.

• There are only 256 possibilities for the value of each octet: the numbers 0 through 255.

• Certain addresses and ranges are designated by the IANA as reserved IP addresses, which mean they have a specific job in IP. For example, the IP address 127.0.0.1 is reserved to identify the computer you're currently using.

What are the steps in a DNS lookup?

DNS is concerned with a domain name being translated into the appropriate IP address. To learn how this process works, it helps to follow the path of a DNS lookup as it travels from a web browser, through the DNS lookup process, and back again. The 8 steps in a DNS lookup:

1. A user types “example.com” into a web browser and the query travels into the Internet and is received by a DNS recursive resolver.

2. The resolver then queries a DNS root nameserver (.).

3. The root server then responds to the resolver with the address of a Top Level Domain (TLD) DNS server (such as .com or .net), which stores the information for its domains. When searching for example.com, our request is pointed toward the .com TLD.

4. The resolver then makes a request to the .com TLD.

5. The TLD server then responds with the IP address of the domain‘s name server, example.com.

6. Lastly, the recursive resolver sends a query to the domain‘s nameserver.

7. The IP address for example.com is then returned to the resolver from the nameserver.

8. The DNS resolver then responds to the web browser with the IP address of the domain requested initially.

9. Once the 8 steps of the DNS lookup have returned the IP address for example.com, the browser is able to make the request for the web page:

10. The browser makes a HTTP request to the IP address.

11. The server at that IP returns the webpage to be rendered in the browser (step 10).

Top Level Domain (TLD)

TLD refers to the last part of a domain name. For example, the .com in amazon.com is the Top Level Domain. The most common TLDs include .com, .net, org, and .info. Country code TLDs represents specific geographic locations. For example: .in represents India. Here are some more examples:

• COM — commercial websites, though open to everyone

• NET — network websites, though open to everyone

• ORG — non-profit organization websites, though open to everyone

• EDU — restricted to schools and educational organizations

• MIL — restricted to the U.S. military

• GOV — restricted to the U.S. government

• US, UK, RU and other two-letter country codes — each is assigned to a domain name authority in the respective country

In a domain name, each word and dot combination you add before a top-level domain indicates a level in the domain structure. Each level refers to a server or a group of servers that manage that domain level. An organization may have a hierarchy of sub-domains further organizing its internet presence, like "bbc.co.uk" which is the BBC's domain under CO, an additional level created by the domain name authority responsible for the U.K. country code.

The left-most word in the domain name, such as www or mail, is a host name. It specifies the name of a specific machine (with a specific IP address) in a domain, typically dedicated to a specific purpose. A given domain can potentially contain millions of host names as long as they're all unique to that domain. (The "http" part stands for Hypertext Transfer Protocol)

Nowadays, you're more likely to see "https" which is a sign the information is being sent by secure protocol where the information is encrypted. A subdomain is a subdivision of a domain name, allowing you to put content in your URL before your namespace.

For example, blog.companyname.com or shop.companyname.com would be a subdomain of the domain name companyname.com. For example: If a customer buys a domain with 123 Reg,

e.g. yourdomain.co.uk, they can set up subdomains,

e.g. site1.yourdomain.co.uk or secure.yourdomain.co.uk. This is an excellent way of breaking up the website if you have different regions, products or even languages.