Computer Network

Computer and Communication

  1. Computing concepts
  2. Generations of Computer
  3. DoD model/ARPAnet
  4. Ping/Traceroute
  5. Topologies
  6. Communication media and medium


The conceptual theories of computing devices starts with the considerations on human brain, our brain uses chemicals to transmit information with high speed electrical signals (primary afferent axons) in the nervous system. Just like the working mechanism of our brain, the computer uses electricity for signals to transmit information.

Both human brain and Computing devices works on signals i.e. either it will be “ON (Start of an action)” or “OFF (end of an action) ” .

The computer uses ON and OFF switches (“binary system in which 1 means ON and 0 means OFF”) based on neurons in our brain which get “ON” or “OFF” signals. Synaptic connections, with which our body parts starts an action or end an action). Basically, Synapses are called “connections between neurons” with which “information” flows from one neuron to another.

The main differences in between computer and computer is that the brains are analogue whereas computers are digital. Moreover, our brain is much faster access (of memories) as compare to modern computers, it uses around 225 million billion interactions between cell types   .

As per Wikipedia “ In Oxford English Dictionary, the first known use of the word “computer” was in 1613 in a book called The Yong Mans Gleanings by English writer Richard Braithwait: “I haue [sic] read the truest computer of Times, and the best Arithmetician that euer [sic] breathed, and he reduceth thy dayes into a short number.” This usage of the term referred to a person who carried out calculations or computations. The word continued with the same meaning until the middle of the 20th century. From the end of the 19th century the word began to take on its more familiar meaning, a machine that carries out computations

Computer is an analytical engine

The Computer is basically an analytical engine, which can perform

  1. A program,
  2. Can carry out calculation
  3. Can make decisions based on carryout calculation


There are four primary distinguishing characteristics of computers , that are:

  1. Fast
  2. Efficient
  3. Storage
  4. scalability

Generation of computers

  1. First Generation of computers (1940-1956) starts with the concepts of “Vacuum Tubes” , which uses magnetic drums for storage .

2.      In Second Generation (1956-1963) , Transistors was replaced by vacuum tubes . With transistors, inventors were able to make computers smaller and faster.

3.      Third Generation (1964-1971) of computers revolutionized the computing theory concepts by the invention of Integrated Circuits, made with semiconductor materials.

4.      Fourth Generation (1971-Present) of computers revealed with the generation of Microprocessors, a tiny silicon chip with thousands of integrated circuits in it.

5.      As knowledge of connections between neurons in human brain prepared scientists to make first generation computers , now-a-days in Fifth Generation (Present and Beyond), scientists are working with the human to human minds interaction mechanisms ( learning or problem solving mechanism ) that highlights towards the creation of intelligent machines that work and react like humans. They called it as  Artificial Intelligence .

Benefits of computer systems –  to communicate with other computers

The real benefit of the computer invention is to systemize them with the help of communication. Communication is the mechanism of joining computers all around the world or beyond in space. The communication makes fully comprehensive and sophisticated computer systems through which we can portray our tasks with other ones, such as through ecommerce portal or ERP systems.

Communication mechanism

Early mechanism of communication was token ring, now we use IP address to communicate with other computer (a computer can be a physical or virtual system) .

Having a large picture of communication mechanism, any device or machine which can respond on PING (packet interNet groper ) and shows its existence is said to be part of computer systems with a valid live IP ( Internet Protocol) address .  Examples of devices are IP Cameras , IP Phones , IP intercom or IP based EMS along with Routers and Firewalls .

As we told earlier that the communication makes fully comprehensive and sophisticated computer systems, it means every type of communication system works with their predefined parameters based on OSI communication models.

let’s suppose we have a CCTV system and  we want to configure a alert system with  CCTV DVR  which will generate an email whenever a motion detects or video loss , we have to define a SMTP port (25) on NVR or DVR system to communicate with our email servers that also works on same SMTP port as predefined port by IEEE .

On the basis of predefined Ports we use unique IP address for each and every device to establish a proper communication mechanism.

OSI Communication MODEL

Every communication starts with this theoretical model called OSI Model:

An OSI Layer based E-Commerce Communication Case study

  • Let’s suppose a person want to go on for shopping, we called this person as end user, it means the user will start working with Application Layer , this layer controls the transferring of requested files ( shopping carts ) .
  • The presentation layer establishes protocols for the handling of the data display.
  • Session Layer basically works with transport layer to allow the end user access to the website. Session layer controls the access until the end user remains logged on to the , it drops automatically whenever the end user terminates or close the website. The Flow control of data is the responsibility of transport layer which checks to ensure that data is correctly received from host (end user) to host ( .
  • The network layer manages SOPs that how communication will take place, it controls the routing packets of data with the best possible shortest available path through firewalls and routers.
  • Data links layer provide “envelope” for the data, It establishes if a link exists to the hierarchy, context and hosted server of as it provides rules how a data can be exchanges through network.
  • The physical layer concerned with the transfer of electrical signals or data bits through cables.

Now taking another practical scenario of OSI model’s working mechanism. Starting with  , its DNS entries available all over the world , it means if a end user starts its session from Australia ,the DNS main servers first checks Site’s  DNS entries against Site’s mapped DNS IP addresses on sub domains finally it gets hosted entry  from china . After verification of DNS , hosting company play its role now , it tells  where the Alibaba’s web server hosted   . The users browser sends “http get” command to web server to make  HTTP or HTTPS request successful  .

Ping termed as packet internet groper  used to check for the presence of another system online. we called ping is completed when it take  “Round Trip Time” (or RTT to takes a packet to reach on a particular server). RTT calculates how long it takes for the packet to reach the server and to be sent back.

trace route is a computer network diagnostic tool for displaying the route (path) and measuring transit delays of packets across an Internet Protocol (IP) network. Trace route takes the history of the route as the round-trip times of the packets. Difference between Ping and trace route is trace route takes consecutive history of every hop (a hop is one portion of the path between source and destination) whereas ping displays final round-trip times from the destination point.

Network Topology Definition

A network topology is the pattern in which nodes (i.e., computers, printers, routers or other devices) are connected to a local area network (LAN) or other network via links (e.g., twisted pair copper wire cable or optical fiber cable).

There are four principal topologies used in LANs: bus, ring, star and mesh. The most widely used of these is bus, because it is employed by Ethernet, which is the dominant LAN architecture. In a bus topology all devices are connected to a central cable, called the bus or backbone. This topology is relatively inexpensive and easy to install for small networks.

In a ring topology each device is connected directly to two other devices, one on either side of it, to form a closed loop. This topology is relatively expensive and difficult to install, but it offers high bandwidth and can span large distances. A variation is the token ring, in which signals travel in only one direction around the loop, carried by a so-called token from node to node.

In a star topology all devices are connected directly to a central computer or server. Such networks are relatively easy to install and manage, but bottlenecks can occur because all data must pass through the central device.

The mesh topology can be either a full mesh or a partial mesh. In the former, each computer is connected directly to each of the others. In the latter, some computers are connected to most of the others, and some are connected only to those other nodes with which they exchange the most data.

The several basic network topologies can be combined in various ways to form hybrid topologies, such as a ring-star network or a tree network. The latter consists of two or more star networks connected to a linear bus.


Media, & when there is more than one Media , we called it Medium

It is a physical substance which responsible to carry voice or data signals. Names of such substances are copper (Example – wire), glass or plastic (Example -fiber-optic cable), or air (Example- radio, infrared, microwave, or satellite). There are two basic types of media.

Wired Media is called Guided media (copper wire and Fiber-Optic) whereas wireless media are those in which the message is broadcast through the air( infrared, microwave, or satellite).

 Fiber Optic Cable

Fiber Optic cable media is expensive but ideal for multiple buildings and for ISPs for customers as it transfers data in GB/Sec.  .

Fiber Optic cable is made of thinnest glass with cladding and coating of polyimide. Core and cladding produce total internal reflection which results fastest transmission of data without any loses. Fiber Optic Cable is used for long distance or high-speed communication.

Wireless Communication

Now-a-Days, In 4G or 5G Cellular era, Wireless communication medium is necessary in our daily life. We normally use Wireless Access Points (APs) for Wireless communication to utilize Radio Frequencies (RF) or Infrared (IR) signals to transmit data on our mobiles and computers/Laptops/Ipads in between offices or departments .Similarly, Router with Access point functionality make it wireless router, we use Wi-Fi signals through Wireless access point to communicate within WLAN, with b, g n and ac standards.

Currently we are working with 802.11a, b, g, n and ac standard based wireless routers, devices with the 802.11ad, ah, aj , ax and ay are in experimental phase .ay is expected to release in 2017 with stream data rate up to 100 Gbit/s .The latest Wireless Communication devices uses  multiple input multiple output (MU-MIMO) technology such as Cisco AP 3700. .

MU-MIMO architecture


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