Internet- Architecture, Internet Service Providers (ISP), Internet Addressing System: IP Address, DNS, URL

Types of IP addresses

1. Private IP addresses

All the devices that are linked with your internet network are allocated a private IP address. It holds computers, desktops, laptops, smartphones, tablets, or even Wi-Fi-enabled gadgets such as speakers, printers, or smart Televisions.

2. Public IP addresses

A public IP address or primary address represents the whole network of devices associated with it. Every device included within your primary address contains their own private IP address. 

Public IP addresses are further classified into two categories- dynamic and static.

• Dynamic IP addresses
  As the name suggests, Dynamic IP addresses change automatically and frequently. With this type of IP address, ISPs already purchase a bulk stock of IP addresses and allocate them in some order to their customers. 
• Static IP addresses
  In comparison to dynamic IP addresses, static addresses are constant in nature. The network assigns the IP address to the device only once and it remains consistent. Though most firms or individuals do not prefer to have a static IP address, it is essential to have a static IP address for an organisation that wants to host its network server. 

Types of website IP addresses

The following classification is segregated into the two types of website IP addresses i.e., shared and dedicated.

1. Shared IP addresses

Many startups or individual website makers or various SME websites who don’t want to invest initially in dedicated IP addresses can opt for shared hosting plans. Various web hosting providers are there in the market providing shared hosting services where two or more websites are hosted on the same server. 

2. Dedicated IP addresses

Web hosting providers also provide the option to acquire a dedicated IP address. Undoubtedly dedicated IP addresses are more secure, and they permit the users to run their File Transfer Protocol (FTP) server.

DNS

An application layer protocol defines how the application processes running on different systems pass the messages to each other.

• DNS stands for Domain Name System.
• DNS is a directory service that provides a mapping between the name of a host on the network and its numerical address.
• DNS is required for the functioning of the internet.
• Each node in a tree has a domain name, and a full domain name is a sequence of symbols specified by dots.
• DNS is a service that translates the domain name into IP addresses. This allows the users of networks to utilise user-friendly names when looking for other hosts instead of remembering the IP addresses.
• For example, suppose the FTP site at EduSoft had an IP address of 132.147.165.50, most people would reach this site by specifying ftp.EduSoft.com. Therefore, the domain name is more reliable than the IP address.

DNS is a TCP/IP protocol used on different platforms. The domain name space is divided into three different sections: generic domains, country domains, and inverse domain.

Generic Domains

• It defines the registered hosts according to their generic behaviour.
• Each node in a tree defines the domain name, which is an index to the DNS database.
• It uses three-character labels, and these labels describe the organisation type.

Country Domain

The format of country domain is the same as a generic domain, but it uses two-character country abbreviations (e.g., us for the United States) in place of three character organisational abbreviations.

Inverse Domain

The inverse domain is used for mapping an address to a name. When the server has received a request from the client, and the server contains the files of only authorised clients. To determine whether the client is on the authorised list or not, it sends a query to the DNS server and asks for mapping an address to the name.

Working of DNS

• DNS is a client/server network communication protocol. DNS clients send requests to the. server while DNS servers send responses to the client.
• Client requests contain a name which is converted into an IP address known as a forward DNS lookups while requests containing an IP address which is converted into a name known as reverse DNS lookups.
• DNS implements a distributed database to store the name of all the hosts available on the internet.

URL

URL stands for Uniform Resource Locator. It is the address of a resource, which can be a specific webpage or a file, on the internet. It is also known as a web address when it is used with http. It was created in 1994 by Tim Berners-Lee. URL is a specific character string that is used to access data from the World Wide Web. It is a type of URI (Uniform Resource Identifier).

Every URL contains the following information:

• The scheme name or protocol.
• A colon, two slashes.
• A host, normally called a domain name but sometimes as a literal IP address.
• A colon followed by a port number.
• Full path of the resource.

The URL of a web page is displayed above on the page in the address bar. A typical URL looks like this:

http://www.example.com/full-form

The above URL contains:

• protocol: http
• host or domain: www.example.com
• Path of the resource: /full-form

A URL can be entered manually by typing it in the address bar of your web browser. If the URL does not contain a valid server, a browser may display a “Server not found” error and if the path in the URL is incorrect, the browser may display a “404 error”. A URL does not contain spaces and uses forward slashes to represent different directories. So, dashes and underscores are used to separate the words of a web address.

Intranet

The intranet is a private network that belongs to a particular organisation. It is designed for the exclusive use of an organisation and its associates, such as employees, customers, and other authorised people. It offers a secure platform to convey information and share data with authorised users. Confidential information, database, links, forms, and applications can be made available to the staff through the intranet. So, it is like a private internet or an internal website that is operating within an organisation to provide its employees access to its information and records. Each computer in the intranet is identified by a unique IP Address.

Some of the benefits of the intranet are:

1. It is cheap and easy to implement and run, and is more safe than the internet and extranet.
2. It streamlines communication that enables the company to share its data, information, and other resources among employees without any delay. The entire staff can receive company’s announcements, ask questions, and access internal documents.
3. It provides a secure space to store and develop applications to support business operations.
4. It improves the efficiency of the company by speeding up workflow and reducing errors. Thus, it helps achieve targets by completing the tasks on time.
5. It offers a testing platform for new ideas before they are uploaded on the company’s internet webpage. Thus, it helps maintain the credibility of the company
6. Information is shared in real-time, or updates are reflected immediately to all the authorised users.
7. Modern intranets also offer a mobile app that allows employees to stay connected on the go.
8. It aids in project management and tracking workflow and teams’ progress.
9. It can work with mobile devices, which means it can provide information that exists on the intranet directly to mobile devices of employees such as phones, tablets, etc.
10. It can also be used to motivate employees, facilitate employee recognition, and to reward them for performing beyond expectations.

Extranet

Extranet is a part of an organisation’s intranet. It is a communication network that is based on internet protocols (TCP/IP). It provides controlled access to the firm’s intranet to its trading partners, customers, and other businesses. So, it is a private network that securely shares internal information and operations of a firm with authorised people outside the firm without giving access to the company’s entire network. The users are required to have IDs, passwords, and other authentication mechanisms to access this network.

Some of the benefits of extranet:

• It acts as a single interface between the company and its trading partners.
• It automates the firm’s processes like automatically placing an order with suppliers when inventory drops.
• It improves customer service by providing customers a platform to resolve their queries and complaints.
• It enables the firm to share information with trading partners without engaging in paper-based publishing processes.
• It streamlines business processes that are repetitive in nature, such as ordering from a vendor on a regular basis.

Limitations of Extranet:

• Hosting: If you host extranet pages on your own server, it requires a high bandwidth internet connection, which may be very expensive.
• Security: You need extra firewall security if you host it on your own server. It increases the workload and makes security mechanisms very complex.
• Dependency: It is dependent on the internet as outsiders cannot access information without using the internet.
• Less Interaction: It reduces the face to face interaction between customers, business partners, vendors, etc., which results in poor relationship building.

TCP

1. TCP stands for Transmission Control Protocol. It is a transport layer protocol that facilitates the transmission of packets from source to destination. 
2. It is a connection-oriented protocol that means it establishes the connection prior to the communication that occurs between the computing devices in a network. 
3. The main functionality of the TCP is to take the data from the application layer. 
4. Then it divides the data into several packets, provides numbering to these packets, and finally transmits these packets to the destination. 
5. The TCP, on the other side, will reassemble the packets and transmit them to the application layer.

Features of TCP protocol

• Transport Layer Protocol

TCP is a transport layer protocol as it is used in transmitting the data from the sender to the receiver.

• Reliable

TCP is a reliable protocol as it follows the flow and error control mechanism. It also supports the acknowledgment mechanism, which checks the state and sound arrival of the data. 

• Order of the data is maintained

This protocol ensures that the data reaches the intended receiver in the same order in which it is sent. It orders and numbers each segment so that the TCP layer on the destination side can reassemble them based on their ordering.

• Connection-oriented

It is a connection-oriented service that means the data exchange occurs only after the connection establishment. When the data transfer is completed, then the connection will be terminated.

• Full duplex

It is a full-duplex means that the data can transfer in both directions at the same time.

• Stream-oriented

TCP is a stream-oriented protocol as it allows the sender to send the data in the form of a stream of bytes and also allows the receiver to accept the data in the form of a stream of bytes. 

FTP

• FTP stands for File transfer protocol.
• FTP is a standard internet protocol provided by TCP/IP used for transmitting the files from one host to another.
• It is mainly used for transferring the web page files from their creator to the computer that acts as a server for other computers on the internet.
• It is also used for downloading the files to the computer from other servers.

The above figure shows the basic model of the FTP. The FTP client has three components: the user interface, control process, and data transfer process. The server has two components: the server control process and the server data transfer process.

There are two types of connections in FTP:

• Control Connection: The control connection uses very simple rules for communication. Through control connection, we can transfer a line of command or line of response at a time. The control connection is made between the control processes. The control connection remains connected during the entire interactive FTP session.

• Data Connection: The Data Connection uses very complex rules as data types may vary. The data connection is made between data transfer processes. The data connection opens when a command comes for transferring the files and closes when the file is transferred.

HTTP

1. HTTP stands for HyperText Transfer Protocol.
2. It is a protocol used to access the data on the World Wide Web (www).
3. The HTTP protocol can be used to transfer the data in the form of plain text, hypertext, audio, video, and so on.
4. This protocol is known as HyperText Transfer Protocol because of its efficiency that allows us to use it in a hypertext environment where there are rapid jumps from one document to another document.
5. HTTP is similar to the FTP as it also transfers the files from one host to another host. But, HTTP is simpler than FTP as HTTP uses only one connection, i.e., no control connection to transfer the files.
6. HTTP is used to carry the data in the form of MIME-like format.
7. HTTP is similar to SMTP as the data is transferred between client and server. 
8. The HTTP differs from the SMTP in the way the messages are sent from the client to the server and from server to the client. 
9. SMTP messages are stored and forwarded while HTTP messages are delivered immediately.

Features of HTTP:

• Connectionless protocol: HTTP is a connectionless protocol. HTTP client initiates a request and waits for a response from the server. When the server receives the request, the server processes the request and sends back the response to the HTTP client after which the client disconnects the connection. The connection between client and server exists only during the current request and response time only.

• Media independent: HTTP protocol is media independent as data can be sent as long as both the client and server know how to handle the data content. It is required for both the client and server to specify the content type in the MIME-type header.

• Stateless: HTTP is a stateless protocol as both the client and server know each other only during the current request. Due to this nature of the protocol, both the client and server do not retain the information between various requests of the web pages.

DHCP : Dynamic Host Configuration Protocol

Dynamic Host Configuration Protocol (DHCP) is a network management protocol used to dynamically assign an IP address to any device, or node, on a network so they can communicate using IP (Internet Protocol). DHCP automates and centrally manages these configurations. 

There is no need to manually assign IP addresses to new devices. Therefore, there is no requirement for any user configuration to connect to a DHCP based network.

DHCP can be implemented on local networks as well as large enterprise networks. DHCP is the default protocol used by most routers and networking equipment.

Components of DHCP

When working with DHCP, it is important to understand all of the components. Following are the list of components:

• DHCP Server: DHCP server is a networked device running the DHCP service that holds IP addresses and related configuration information. This is typically a server or a router but could be anything that acts as a host, such as an SD-WAN appliance.
• DHCP client: DHCP client is the endpoint that receives configuration information from a DHCP server. This can be any device like computer, laptop, IoT endpoint or anything else that requires connectivity to the network. Most of the devices are configured to receive DHCP information by default.
• IP address pool: IP address pool is the range of addresses that are available to DHCP clients. IP addresses are typically handed out sequentially from lowest to the highest.
• Subnet: Subnet is the partitioned segments of the IP networks. Subnet is used to keep networks manageable.
• Lease: Lease is the length of time for which a DHCP client holds the IP address information. When a lease expires, the client has to renew it.
• DHCP relay: A host or router that listens for client messages being broadcast on that network and then forwards them to a configured server. The server then sends responses back to the relay agent that passes them along to the client. DHCP relay can be used to centralise DHCP servers instead of having a server on each subnet.