Structure of the Internet

Internet

The internet is one of humanity’s most impressive inventions. What started as a small network of local knowledge-sharing data repositories has become a worldwide phenomenon that has changed our lifestyle. The internet often referred to only as “Net,” is an interconnection of worldwide computers in the form of a network. The term is also defined as a network of networks through which users can, whether they have authorization to do so, access knowledge from some other computer (and sometimes communicate directly to clients on different computers). There is a wide variety of public networks that include LANs, WANs, and MANs. Still, technically, the Transmission Control Protocol/Internet Protocol application distinguishes the internet from private networks. However, intranet and extranet also employ the same TCP/IP interface that are advanced adaptations of the internet.

Basics of the internet

It was developed by the U.S. government’s Advanced Research Projects Organization (ARPA) in 1969 and was first identified as the ARPANet. This network’s primary aim was to establish a connection between the research labs of Universities for research purposes.  The secondary objective of ARPANet was to secure messages in case of a military attack or disaster, as the messages were routed or rerouted in a direction.

Structure of the Internet

1. Internet Address:

Computers connected to the internet means that the systems are connected to computers’ worldwide network. Therefore, each machine/device has its own or unique address. Addresses of the internet are in the form “kkk.kkk.kkk.kkk,” where each “kkk” ranges from 0-256. This structure of the internet address is known as an IP address (Internet Protocol). Fig. 1 describes the connection between two computers using the internet. Both systems have unique IP addresses. However, the internet is a unique object between both systems.

 If a client connects the computer with the internet using Internet Service Provider (ISP), the client’s system is allocated a temporary internet protocol address till the session client is operating. However, if someone becomes part of the internet using a local area network (LAN), the client is probably assigned to a permanent internet protocol. At the time of connection, the system will have a unique internet protocol address. A handy program is named “Ping” to ensure the internet connection on the system; this provision is available on all the Microsoft Windows operating systems and sometimes on a flavour of Unix OS.

2. Protocol Stacks and Packets

As the device is connected to the internet and retains a unique address. What is the procedure to communicate the device with the system at another end? For the sake of understanding, we are considering an example. As we discussed in Figure 1, one system retains an IP address, i.e., 173.196.95.98, and the second system contains an IP address, i.e., 162.194.60.98. Suppose you want to send a message “Hello Friend” to another computer via “Your computer”. The medium of communication will be the wire that connects “Your computer” to the internet. Suppose you are using ISP facilities, then the message will be communicated via the phone line of ISP. In such a case, the first message will be encrypted in digital form. All the alphanumeric characters will be converted into an electronic signal. The electronic signal will be delivered to the other computer and then again decrypted into the original form as received on the second IP system. The convergence of messages from alphanumeric form to a digital signal and vice versa is performed employing Protocol Stack that is part of each operating system, i.e., Windows, Unix, Android, etc. The protocol stack applied in the domain of the internet is known as TCP/IP, as it is the primary protocol used for communication.

Fig. 2 briefly describes the path framework related to that message from “Your computer” to another computer.

1.  The message that needs to be sent is written in an application on “Your computer” it starts from the top using the protocol stack and moves downward.
2. If the message is large, the stack layer breaks the message into smaller chunks so that data management remains stable. The chunks of data are known as Packets.
3. The data from the application layer move towards the TCP/IP layer. The packet of the data is assigned with a port number. In computers, various types of message applications are working at a time. Therefore, it is essential to know which application is sending the message so that it needs to be synced at the reception level (another computer) with the same application. Hence, the message will listen on the same port.
4. After necessary processing at the TCP level, the packets move towards the IP layer. The IP layer provides the destination layer where the message should be received. At this level, message packets retain port number as well as IP address.
5. The hardware layer is responsible for converting alpha/numeric messages into a digital signal and sending the message through the telephone’s path.
6. Internet services provider (ISP) is also attached to the internet, where the ISP router examines the recipient’s address. The next stop of the packet is another router.
7. Eventually, the packets reach another computer. This time packets start from the bottom.
8. As the packets move upwards, the packets’ unnecessary data is removed that was helping to reach the destination; this includes IP address and port number.
9. On reaching the stack’s top, all the packets are reassembled to form the original message sent by “Your computer”.

3. Infrastructure of the Network:

It is clear from the discussion about how two computers at different locations interact with each other employing the internet. How do computers send messages? How are packets transmitted and received at both systems? How an alphanumeric message is converted into a digital signal and vice versa. Fig. 3 will now briefly explain what resides in between all the layers?

Fig. 3 is the brief description of Fig. 1, where physical connection via telephone to ISP is easy to guess, but it also requires some explanation. The ISP manages a pool of modems; this is handled by some device that contains data flow from the modem pool to a spine or specific line router (usually a specialized one). This configuration can be linked to a port server, as it offers network connectivity. Information on billing and use is typically obtained here as well.

When the packets cross the phone framework and nearby ISP equipment, it is redirected to the ISP’s mainline or infrastructure from which the ISP purchases bandwidth. The packets typically pass from here to many routers, backbones, unique lines, and other networks to reach the target, the device with another computer’s address.

For the users of Microsoft Windows and operators of Unix flavour, if you have an internet connection, you can trace the packets’ path by using an internet program known as traceroute. Just like the PING command, users can check the packet path in the command prompt. Traceroute prints all the routers, computer systems, and various other entities related to the internet from the packet will travel and reach the actual destination. The internet routers decide further communication of packets. Multiple packets are shown in Fig. 3; the real cause of such routers is to understand the networking structures clearly. 

The infrastructure of the internet:

The framework of the internet consists of multiple interconnected large networks. The large networks we called Network Service Providers (NSPs). UUNet, IBM, CerfNet, SprintNet, PSINet are well-known examples of NSPs. Packet traffic is exchanged among these peer networks. Each of the NSPs needs to be connected to three Network Access Points (NAPs). In NAPs traffic, packets have the provision to jump from one NSP to the backbone of another NSP. Metropolitan Area Exchange (MAEs) are also interconnected utilizing NSPs. MAEs and NAPs have the same functionality; however, MAEs are owned privately.

Consequently, the original interconnection points were NAPs. In contrast, both (MAEs & NAPs) are referred to as Internet Exchange Points (IXs). NSPs provide services to other smaller networks that include ISPs. However, the backbone of a single NSP infrastructure is quite complicated to draw. However, mostly NSPs publish their infrastructure on the web related to networking maps. Drawing an accurate map of the internet is impossible due to several complexities that include size and evolution (change in structure) are the majors.

Hierarchy of the Internet:

Various questions arise in mind regarding the networking and communication path. We will try to announce these queries and then will discuss the patterns for their solution.

1. How do packets come to know their path of the moment on the internet?
2. Devices connected to the internet know the location (digitally) of other computers related to the internet?
3. Do packets only get “broadcast” to each device connected to the internet?

Here, “No,” any computer knows the location of any other computer connected to the internet. Packets are not received & transmitted to every device connected to the internet. Information related to the destination is embedded in the routing tables, routers connected to the web.

A router is a device that is a sort of bridge between the networks for routing the packets among them. Routers are familiar with all the sub-networks and the IP address used inside the connected networks. However, the router is unaware of the IP address that lies above it. Fig. 4 briefly describes the internet routing hierarchy.

The black boxes designed in Fig. 4 represent the routers. The whole NSP networking backbone relates to NAP. Under the NAP layer, there are various sub-networks. The lowermost layer illustrates a local area network (LAN) on both ends where several computers are connected.

On the arrival of a router packet, it examines the internet protocol (IP) and puts there an IP layer on the originating device. The router checks the routing table. If an IP address exists in the network, the packet is dispatched to the network; however, routes transmit this packet towards the default router if the IP address does not exist, generally, to the next router that resides in the hierarchy. Similarly, if the next layer (routers) finds the IP address, the packet will be sent to the device, and if no address is found, it is shifted upwards to the backbone of the NSP. There exists an enormous routing table at the backbone of the NSP. The packet will be dispatched to the real backbone at this stage, and it will start moving downward via smaller networks until it reaches the destination.

Domain Name Service (DNS):

Domain name service (DNS) is a distributed database that assists in tracking the names of devices and the integrated internet protocol addresses present on the internet. Multiple devices are connected to the internet host part of the domain name service database and the software which permits the others to access it. Such systems are also called DNS servers. DNS server only holds a subset of the database, not the entire database. Therefore, if a computer requests a domain name not present in the DNS server, it redirects the computer towards a new DNS server. The hierarchy of the DNS is just similar to the structure of the internet protocol routing hierarchy.

Whenever an internet connection is established, single primary and one or greater than one secondary DNS servers become part of the installation. The best example of the DNS is whenever a client requests to browse a website, the web browser first connects with the primary DNS server from where it will achieve the IP address for the domain name as requested by the client. Then the browser will be associated with the target device to open the web page.

Application Protocols on the Internet:

People use the internet for their facilities. Businesses and individuals are of no means if they are not linked with the internet. The primary thing that makes the interface between the users and networks are the applications. Emerging technologies are of no use if there is not a good interface for their operation. In the below discussion, we will briefly depict the significance of application protocol on the internet. That makes the businesses fluent, efficient, and more robust.

World Wide Web (WWW):

The world wide web (www) is the most common service on the internet—the networks based on an application known as Hypertext Transfer Protocol (HTTP). Web pages are built by using a specific language known as Hypertext Markup Language (HTML). Over the internet, web browsers and servers converse with each other with the help of HTTP. The protocol is the application level as it is present on the top of the TCP layer. In such a case, web browsers and servers are the applications.

A few steps are followed whenever a client requests to open a website in the web browser.

1. Most of the clients use the domain name to open the URL in the browser to connect with DNS that will retrieve the integrated IP address.
2. A connection is established among the web browser and web server, where an HTTP requires, is submitted to explore the desired page on the web.
3. Upon receiving the request at the webserver level, it checks the requested web page’s presence. If the web server finds the web page, it will send the page; otherwise, it will send an error containing “HTTP 404 Error”.
4. The connection is made closed once the web browser will receive the requested web page from the web server.
5. The web browser then parses each element residing in the requested web page.
6. A few connections are established from the HTTP request’s perspective to adjust the text, images, and styling of the requested web page inside the web browser.
7. After getting all the elements and adjusting them accurately, the web page is loaded and displayed in the web browser.

Electronic Mail (e-mail):

The internet is used for maintaining connections. One of the most excessively used applications used over the internet is e-mail. The application-level protocol used for e-mail is known as Simple Mail Transfer Protocol (SMTP) based on text. However, SMTP is link oriented, unlike HTTP. SMTP is a complex protocol as compared with the HTTP. But the variety of commands is wide in SMTP.

1. Whenever a client receives an e-mail, the pattern adopted in the whole scenario is as given below.
2. Mail clients that may be Microsoft Outlook, Google Mail, Netscape Mail, Yahoo Mail, etc., open a connection with the mail server. DNS or IP address of the mail server is installed automatically whenever the mail client is installed in the operating system.
3. For identification at the initial level, the mail server transmits a message.
4. Depending upon the mode of a client like either one is sending or checking the mail. A suitable SMTP will be dispatched to the server. The web server will then respond accordingly.
5. he same process will remain carry till the client sends a command “SMTP QUIT”. The connection will be closed after that quit command.

Summary and Facts:

The internet is one of the most useful inventions. By the passage of time, the requirements and worth of the internet are extensively increasing. Various firms, organizations, enterprises, and businesses are now getting benefits from this revolutionary technology. As the internet is a network of networks, therefore a good structure is present. The internet structure is built up of packets and routers as a whole the traffic is depending upon them. Addresses are embedded in the headers of packets. We will recall a few questions here to get useful insights from this article.

What is the internet?

• What started as a small network of local knowledge-sharing data repositories has become a worldwide phenomenon that has changed our lifestyle.
• The term is also defined as a network of networks.
• There is a wide variety of public networks that includes LANs, WANs, and MANs.
• Application of Transmission Control Protocol/Internet Protocol (TCP/IP) distinguishes the internet from private networks.

What are the basics of the internet?

• Developed by the U.S. government’s Advanced Research Projects Organization (ARPA) in 1969 and was first identified as the ARPANet.
• The network aimed to establish a connection between the research labs of Universities for research purposes.

What is included in the structure of the internet?

1.      Internet Address:

• Each machine/device has its own or unique address.
• Addresses of the internet are in the form “kkk.kkk.kkk.kkk,” where each “kkk” ranges from 0-256.
• The structure of the internet address is known as an IP address (Internet Protocol).
• A handy program named “Ping” is used to ensure internet connection.

2.      Protocol Stock and Packets

• The convergence of alphanumeric message into digital form and again from the digital form with the ISP communication medium’s help is done by providing various layers that include the application layer, TCP layer, IP layer, and hardware layer.

3.      Complete Infrastructure

• The framework of the internet consists of multiple interconnected large networks.
• The large networks we called Network Service Providers (NSPs).
• Each of the NSPs needs to be connected to three Network Access Points (NAPs).
• In NAPs traffic, packets have provision to jump from one NSP to the backbone of another NSP.
• Metropolitan Area Exchange (MAEs) are also interconnected utilizing NSPs. MAEs and NAPs have the same functionality; however, MAEs are owned privately.
• NSPs provide services to other smaller networks that include ISPs.

References:

1. https://searchwindevelopment.techtarget.com/definition/Internet
2. https://www.webfx.com/blog/internet/the-structure-of-the-internet-infographic/
3. https://www.informit.com/articles/article.aspx?p=2963467&seqNum=4
4. https://web.stanford.edu/class/msande91si/www-spr04/readings/week1/InternetWhitepaper.htm
5. https://www.ccexpert.us/operating-systems/describe-internet-protocols-and-applications.html