SIM  (Subscriber Identity Module)

 A sim is a tinny computer cheap card that gives a cellular device its unique phone number.  It contains all the credentials which important to connect to any cellular network. Current SIMs typically have 16 to 64 kb of memory which used for storing personal phone numbers, text messages, and other data.

SMS  (Short Message Service)

SMS is the transmission of short text messages to and from a mobile phone, fax machine, and other devices. The message must be no longer than some fixed number of alphanumeric characters and contain no images or graphics.

MMS  (Multimedia Message Service)

It is a standard messaging service to send multimedia content to and from any mobile phone over Cellular network. This includes images, videos, and sound files.

E-mail  (Electronic mail)

It allows you to send and receive messages to and from anyone with an email address anywhere in the world. Email address is a unique address for every user, required to receive and send emails. Photos documents and other files can be attached to an email so that more information can be shared.

Voicemail

A Voicemail system is a Computer Based system that allows users and subscribers to exchange personal voice messages.

Video Conferencing

A technology that allows users in different locations to hold face to face meetings without having to move to a single location.

Chat

Online textual talk in real-time is called chatting. In chatting we type a message on our screen, which is immediately received by the recipient then the recipient can type a message in response to our message which is received by us instantly.

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Wireless Communication

Wireless communication means the method of transferring information between computing devices without using any physical connection. For example- when we try to access any agency database server from our mobile phone without using any physical connection. Not all wireless technologies are mobile technology.  In wireless communication device is continuously connected to the base network.

Mobile Communication

Mobile is a device that is portable. Mobile communication is based on a cellular network. A cellular network is nothing but a radio network. A mobile device may be a PDA, smartphone, laptop, and any other device that allows the user to complete computing tasks without connection with any other wireless network. In this communication, the device is not continuously connected to the base or central network.

Mobile Communication Technologies

GSM: GSM stands for a global system for mobile communication which is one of the leading digital cellular systems. The GSM standard for Digital cell phones was established in Europe in the mid 9080s. It becomes the International standard in Europe, Australia, and much of Asia and Africa. Cell phones users can buy one phone that will work anywhere where the standard is supported. To connect to the specific service providers in different countries, GSM users simply switch SIM cards. They stores all the connections and identification numbers to access a particular wireless service provider.

CDMA: CDMA stands for code division multiple access. CDMA is designed by Qualcomm in the United States. It is used second and third generation of the wireless communication. It is a digital cellular technology that uses spread spectrum techniques. Because of spread spectrum  is it it maintains high security and noise reduction. In this techniques several transmitters can send information simultaneously over a single communication channel.

Network Protocol / Communication Protocol

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In information technology, a protocol is the special set of rules that two or More computer on a network follows to communicate with each other. A protocol defines how computers identify one another on a network and how this information reaches its Final Destination.  A protocol is needs every time we want to perform any task on the network. It may be transferring data or taking a printout on a network printer for accessing the central database. Each network uses different protocols.

Hypertext: Hypertext is the text that is specially coded using a standard coding language called HTML which basically creates hyperlinks. These hyperlinks can be text, graphics, image, sound, and videos that are used to link users to some other file.

Some most common protocols are below:

HTTP

HTTP  is the protocol that is used for transferring hypertext between two computers and it is particularly used on the world wide web. HTTP is a TCP/IP based communication protocol and provides a standard for web browsers and servers to communicate. HTTP is based on the client-server principle. When a connection established between two computers the client computer sends the request to the server and server response to the request.

FTP (File Transfer Protocol)

This is the simplest and oldest protocol. It is designed for transferring files of any type (ASCII or binary) from one system to another on the internet. FTP is an application protocol that uses the internet's TCP/IP protocols. FTP based on the client-server principle. By giving the FTP command with any remote address we can send and receive files.

TCP/IP (Transmission Control Protocol / Internet Protocol)

TCP/IP are the two protocols that are used together and they form the backbone protocol of the internet. TCP/IP has two major components TCP and IP.

1. TCP: It breaks the data into packets that the network can handle efficiently. It manages the assembling of a message or file into smaller packets that are transmitted over the internet. It verifies all the packets when they arrived at the destination computer and then reassembles them in proper order. Data can be lost in the intermediate network, so TCP adds supports to detect errors or lost data and to Trigger transmission until the data is correctly and completely received.
2. IP: The internet protocol (IP) handles the address part of each packet so that it reaches the right destination. It gives a distinct address (called an IP address) to each data packet. It checks this address to see where to forward the message and finally they reassembled at the destination.

PPP (Point to Point Protocol)

PPP is a communication protocol used to establish a direct connection between nodes. It connects nodes without using any device or any host. It is used over phone lines and any other physical cable. It basically designed to help communication between two systems through telephone lines.

Telnet

Telnet is the main protocol for creating a connection with a remote machine. It allows us to connect with a remote computer over a TCP/IP network or internet. Once our Telnet client establishes a connection to the remote host our clients become a virtual terminal, allowing us to communicate with the remote host from our computer with whatever privileges you have been granted to the applications and data on the host computer.

SMTP (Simple Mail Transfer Protocol)

SMTP is a set of communication protocols that allow the software to transmit an e-mail over the internet. It is a program used for sending emails to other users based on e-mail addresses.

Types of Computer Network

A computer network means a group of networked computers. A network can be a small group of linked computers or can be a large group. Thus networks vary in size and complexity.  There can be four types of networks on the basis of geographical spread.

1. Personal area network (PAN)
2. Local area network (LAN)
3. Metropolitan area network (MAN)
4. Wide area network (WAN)

Personal area network (PAN)

A personal area network organized around an individual person, typically within a 10-metre range. For example- a person has a laptop, mobile phone, PDA and any portable printer all are connected with a single Wi-Fi network.

Local area network (LAN)

A local area network is a computer network that interconnects computer within a limited area such as Residency, School, laboratory, University campus, or office building.  The key purpose of a LAN  is to serve its user in resource sharing. The hardware, as well as software resources, are shared through LANs.

Metropolitan area network (MAN)

Metropolitan Area Network is the networks spread over a city.  For example -  cable TV Network that is spread over a city. It is just a bigger version of LAN and normally uses similar Technology. MAN is also the sharing of hardware and software resources along with its user.

Wide area network (WAN)

The network spread across the large geographical area like countries are known as wide area networks. A wide area network is a group of LANs that are spread across several locations and connected together to look like one big LAN.  Wide area network link offers computer to exchange information at laser costs and higher speeds. The internet is the largest WAN,  spanning the entire Earth.

Data Channel

A Data Channel is a medium used to carry data or information from one point to another point.

Baud

Baud is a unit of measurement for the information carrying capacity of a communication channel. The baud is synonymous with bps (bits per second).

1 Baud = 1 bps

Bandwidth

Bandwidth is the difference between the highest frequency signal component and the lowest frequency signal component. Frequency is measured in Hertz which is denoted by Hz. Hz can be also called Cycles per second.

1 Kilohertz (KHz) = 1000 Hz

1 Megahertz (MHz) = 1000 KHz

1 Gigahertz (GHz) = 1000 MHz

1 Terahertz (THz) = 1000 GHz

Data Transfer Rates

Data Transfer Rate is the speed with which data can transmit from one computer to another. This can be measure from, amount of data transferred per second by any device.

The data rate is measured in units of Bits per second (bps), Bytes per second (Bps), and Baud.

1 Byte = 8 bit

Bit based transfer rates

1000 bps = 1kbps

1000 kbps = 1 mbps

1000 mbps = 1 gbps

1000 gbps = 1 tbps

Byte based transfer rates

1000 Bps = 1 Kbps

1000 Kbps = 1 Mbps

1000 Mbps = 1 Gbps

1 Gbps = 1 Tbps

Node, Server, and NIC

Node/Workstation

Node (workstation): A computer becomes a node when it attached to a network. If there are no notes there would be no network.

Server: a computer that facilitates the sharing of data, software, and hardware resources on the network is known as the server. A network can have more than one server. Each server has a unique name by which it is identified by all the nodes on the network.

Server

A server can be of two types:

1. Dedicated Server
2. Non-Dedicated Server

1) Dedicated Server: In Big networks, one computer is reserved for the server's job it helps all nodes to access data, software, and hardware resources. Since it does not double up as a workstation but only manages the network. So, it is known as dedicated server and such types of networks are called Master-Slave networks.

2) Non-Dedicated Server: In small networks, a workstation can double up as a server. These servers are known as Non-Dedicated Servers. Such types of networks are known as peer-to-peer networks.

Network Interface Unit (NIU)

 A Network Interface Unit (NIU) is a device that is attached to each of the nodes and the server which helps to establish communication between the server and node. Without this computers will not be able to perform the operation on network. The NIU basically acts as an interpreter and is also known as Terminal Access Point (TAP) or Network Interface Card (NIC). The manufacturer assign a unique physical address to each NIC and this physical address is known as the MAC address.

Switching Techniques means techniques from which data are transmitted across networks. The Three Types of switching techniques are employed to provide communication between two computers on a network are:

1. Circuit Switching 
2. Message Switching
3. Packet Switching

1) Circuit Switching 

circuit switching is a technique that directly connects the sender and the receiver in an unbroken path. With this type of technique, once a connection is established a dedicated path exists between both ends until the connection is terminated. For example, telephone switching equipment establishes a path that connects the caller's telephone to the receiver's telephone by making a physical connection. The important property of this switching technique is to an end-to-end path between computers Before any data can be sent.

2) Message Switching

In this technique, the source computer sends data for the message to the switching office first, which stores the data in its buffer. It then Looks for a free link to another switching office and then sends the data to this office. This process is continued until the data are delivered to the destination computers. This type of network is called a store and forward network.

3) Packet Switching

in the packet switching method, the message is broken into small parts, called packets. Each packet is tagged with appropriate source and destination addresses. Data packets can be stored in the main memory instead of the disc there for access delay and costs are minimized also the transmission speeds between nodes are optimized.

Evolution of networking

The evolution of networking has started way back in 1969 by the development of ARPANET, which was the first to the development of the Internet.

ARPANET

In 1969, the world's first network was developed and networking was started with the development of ARPANET. The US Department of Defense sponsored a project named ARPANET (Advanced Research Projects Agency Network) whose goal was to connect computers at different universities and US Defence. Soon the engineers, Scientists, Students, and Researchers who were also able to play long-distance games and socialize with people who share their interests.

In the mid-1980s another federal agency, the national science foundation created a new high capacity network called NSFnet (National Science Foundation Network) which was more capable than ARPANET. NSFnet allowed only the academic research on its network and not any private business on it. So, many private companies built their own networks, which were later interconnected along with ARPANET and NSFnet to form the Internet.

ARPANET was shut down in 1990 and NSFnet was shut down in 1995.

Internet

The Internet is a worldwide network of computer networks that developed from the first network ARPANET. The internet is made up of many small networks each run by different companies. and interconnected at the peering point (Point where two networks connect or exchange data). It is an interconnection of large and small networks around the globe. The Internet allows users to communicate with another user which is connected to another network. 

The internet is a supernetwork it allows all the computers to exchange information with each other. Internet uses a common set of rules to communicate which are called Protocols and the internet uses a set of protocols called TCP/IP (Transmission Control Protocol / Internet Protocol). 

Interspace

Interspace is a client/server software program that allows multiple users to communicate online with real-time audio, video, and text chat in dynamic 3D environments.

an interspace is an advanced form of the internet where users communicate in multiple ways from multiple sources.

Introduction of Computer Network.

When two or more computers linked together for the purpose of sharing (sending/receiving) data and information, known as Computer Network.

Computer Network

Network Goals and Applications

• Resource Sharing: The hardware devices like printers and scanners can be shared over a Network. This reduces costs by reducing the number of hardware items.
• Storage Sharing: On a network, the user can access the data of another machine and can store data on another machine.
• Reliability: A file can have copies on two or three different computers. So, if one is not available other copies can be used.
• Access to a remote database: User can access the Host computer at his PC and send the request. For example - users can make flight reservations, book hotels, and so on anywhere in the world with instant confirmation.
• Communication Facilities: Network provides us facilities to communicate with others via Emails, Chats, Video conferencing, and so on.

Disadvantages of Networking

• Complex: Systems are more complex to run.
• Server fails: If all data are held centrally in a server. It may create problems if the central server fails.
• Expensive to install: Cables, Network devices, NIC, and Softwares required for installation of the network. And these are quite expensive.

We all know what Network is and what it can do. But the problem is how can we link computers to make a network? What structure should we follow to making a network? The solution to all these problems is Topology. Today in this blog we will know about Topology.

Network Topology

Before going deep in Topology we should know about Point-to-Point Link first.

point to point link-point to point link has two ends transmitter and receiver. the main characteristic of point to point link is that each transmitter transmits data to exactly one receiver and each receiver receives data from exactly one transmitter. In other words, we can say that it is two computer's link in which each computer can send or receive data directly from each other without any interruption of other computers.

Point to Point Link

The pattern in which computers/Nodes linked with a network known as Topology. Topology can be of 6 types-

• Bus Topology
• Star Topology
• Mesh Topology
• Ring Topology
• Tree Topology
• Graph Topology

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Let's explain all of this one by one 

Bus Topology:  Bus Topology is also known as Linear Topology. In this type of Topology each node attaches directly to a common cable which is known as the 'Backbone Network' when any computer wants to send data, all computers on the network receive the information but only one accepts the information. In this Topology, cable termination is required cable cannot be left unterminated.

Bus Topology

Advantages:

• Reliable, easy to use, and easy to install.
• Additional nodes can easily connect to the existing network at any point.

Disadvantages:

• Fault detection and isolation is difficult.
• In any case, the failure of the Backbone Network can affect all devices in the network. 

Star Topology: A Star Topology consists of devices connected by Point to Point link to a central Hub or Server. 1t

is easy to control and traffic flow is simple. Dala travels from the sender to the central hub and then to the receiver.

Advantages:

• Single connection failure does not affect the entire network.
• Fault detection is easier
• It is easy to add a new node without disturbing the entire network.

Disadvantages:

• If central Hub fails, the whole network fails.
• Needed a large number of cables so, it increases installation charges.

Mesh Topology: In this Topology each node in network creating Point to Point link with all nodes.

Advantages:

• Single connection failure does not affect the entire network.
• Fault detection is easier
• Every computer has multiple ways to transfer or receive data.

Disadvantages:

• Difficult to add a new node.
• Needed a large number of cables so, it increases installation charges.

Ring Topology: In this Topology, each node directly connected to two or only two neighbor computers. Data travels node to node only in one direction around the circle. That's why this Topology is also known as Circular Topology.

Advantages:

• Reliable, easy to use, and easy to install.
• Additional nodes can easily connect to the existing network at any point.
• Less expensive

Disadvantages:

• Fault detection and isolation is difficult.
• The failure of any node of the network can affect all devices in the network. 

Tree Topology: This topology makes a tree in its structure that's why it is known as Tree Topology. This is a combination of Bus and Star topology. Many hubs directly connected to the Bus and computers directly connected to the hubs.

Advantages:

• Error detection and correction is easy.
• Additional nodes can be added easily.

Disadvantages:

• When many segments added, Maintenance becomes difficult.
• The failure of the backbone network can affect all devices in the network. 

Graph Topology: This Topology is a mixture of all topologies. In this topology, every node has many ways to send data to the other computers.