OSI Reference Model

OSI(Open System Interface) model is developed by the International organization of Standardization (ISO) and referred as ISO-OSI Model.

Today we have two reference model: OSI model and TCP/IP reference model.

OSI model is theoretical but TCP/IP is absolute practical model.

A tribute to Maulana Abul Kalam Azad

Today i.e 11th of November, is birth anniversary of eminent  Scholar, freedom fighter & a man who devoted his life towards nation building Sayyid Maulana Abul Kalam Muhiyuddin Ahmed Azad, popularly known by Abul Kalam Azad.  He was an Indian scholar and a senior political leader of the Indian independence movement. He strongly opposed two nation's theory led by Jinnah during the Pre-Independence and during that time. During the independence, he stayed in India after refusing to go to Pakistan, and became the first Minister of Education in the Indian government. After the India's partition, Azad took up responsibility for the safety of Muslims in India, touring affected areas in Bengal, Bihar, Assam and the Punjab, guiding the organisation of refugee camps, supplies and security. Azad gave speeches to large crowds encouraging peace and calm in the border areas and encouraging Muslims across the country to remain in India and not fear for their safety and security. Amidst communal turmoil following the partition of India, he worked for religious harmony. As India's Education Minister, Azad oversaw the establishment of a national education system with free primary education and modern institutions of higher education. He is also credited with the establishment of the Indian Institutes of Technology and the foundation of the University Grants Commission, an important institution to supervise and advance the higher education in the nation.

Maulan Abul Kalam Azad was master in  several languages, including Urdu, Hindi, Persian, Bengali, Arabic, and English. He was also trained in the Mazahibs of Hanafi, Maliki, Shafi'i and Hanbali fiqh, Shariat, mathematics, philosophy, world history and science by reputed tutors hired by his family. He died on 22 February 1958 at aged 69. In the year 1992, he was posthumously awarded India's highest civilian award, the Bharat Ratna.

Happy Diwali

Wish you and your family members a very Happy and Prosperous Deepawali!!!!!!!!!!!!!!!!

May this festival of light brings you a lot of Peace & Happiness.

Type 1 Vs Type 2 Virtualization

Types of Virtulization:-

Type-1: native or bare-metal hypervisors:
These hypervisors run directly on the host's hardware to control the hardware and to manage guest operating systems. For this reason, they are sometimes called bare metal hypervisors. A guest operating system runs as a process on the host. ex: VMware ESX/ESXi and Microsoft Hyper-V.


Type-2: hosted hypervisors:
These hypervisors run on the top of the OS just as other computer programs do. ex: VMware Workstation, VMware Player and VirtualBox .

List of Android Tricky Codes Useful in Many Cases

Here Some of the list of Android Secret Codes with descriptions. These are very useful.

Code	Description
*#*#4636#*#*	Display information about Phone, Battery and Usage statistics
*#*#7780#*#*	Restting your phone to factory state-Only deletes application data and applications
*2767*3855#	Complete wiping of your mobile also it reinstalls the phones firmware
*#*#34971539#*#*	Shows completes information about the camera
*#*#7594#*#*	Changing the power button behavior-Enables direct power off once the code enabled
*#*#273283*255*663282*#*#*	For a quick backup to all your media files
*#*#197328640#*#*	Enabling test mode for service activity
*#*#232339#*#* OR *#*#526#*#*	Wireless Lan Tests
*#*#232338#*#*	Displays Wi-Fi Mac-address
*#*#1472365#*#*	For a quick GPS test
*#*#1575#*#*	A Different type GPS test
*#*#0283#*#*	Packet Loopback test
*#*#0*#*#*	LCD display test
*#*#0673#*#* OR *#*#0289#*#*	Audio test
*#*#0842#*#*	Vibration and Backlight test
*#*#2663#*#*	Displays touch-screen version
*#*#2664#*#*	Touch-Screen test
*#*#0588#*#*	Proximity sensor test
*#*#3264#*#*	Ram version
*#*#232331#*#*	Bluetooth test
*#*#7262626#*#*	Field test
*#*#232337#*#	Displays Bluetooth device address
*#*#8255#*#*	For Google Talk service monitoring
*#*#4986*2650468#*#*	PDA, Phone, Hardware, RF Call Date firmware info
*#*#1234#*#*	PDA and Phone firmware info
*#*#1111#*#*	FTA Software version
*#*#2222#*#*	FTA Hardware verion
*#*#44336#*#*	Displays Build time and change list number
*#06#	Displsys IMEI number
*#*#8351#*#*	Enables voice dialing logging mode
*#*#8350#*#*	Disables voice dialing logging mode
##778 (+call)	Brings up Epst menu

How to run android Operating system in your desktop or laptop?

There are different ways to run android applications in desktop/laptop platform. We can list out many differences in-between mobile phone/smart phone and desktop/laptop both in hardware and software.  The main different is heterogeneity in processor architecture. Android supports 3 type of processor architectures: ARM, Intel and MIPS and among them ARM is most popular.  However, normal laptop/desktop has processor of Intel x86 or x64 architecture. So, the incompatibility is clearly visible in the current scenario.

To solve this problem, The Android-x86 Project has ported Android operating system to the x86 platform from ARM.  The Android-x86 is an open source project  licensed under Apache Public License 2.0.  The source code for all the latest Android operating system are available on the The Android-x86 Project website.

Now, actual question is not answered. Android operating system can run as a virtual machine like other operating system such as windows or Ubuntu. So, we need a hypervisor to install the android VM. This can be done using Virtualbox or VMware workstation. So, before installation, we have to download any virtualization software(i.e. Virtualbox or VMware workstation) and Android-x86 image file.

Once Virtualbox is installed in the system, we can create a Virtual Machine (VM) after giving proper configuration. Now the next step is to boot the Android-x86 image VM that we have created.

Links:

http://www.android-x86.org/

http://www.android-x86.org/getsourcecode

https://www.virtualbox.org/

http://www.vmware.com/in/products/workstation

Happy Durga Puja

Wish you all Happy Durga Puja.

Eid Mubarak

Eid Mubarak to ALL my dear Friends, Family members, Brothers, Sisters.

Muslims performing Eid prayer at Jama Masjid, New Delhi, India

How to Write an Essay - MOOC Course

Hi, recently I have registered the online MOOC course conducted by Berkley University on the topic "How to Write an Essay".  The course is conducted by UC Berkeley, California, under the instructor  Maggie Sokolik, Ph.D. It is dedicated to those people/students  who want to write good English, and to improve their English speaking. I had the intention to improve my written English, and I think this is the right place. If you would like to join, please go through this link.

The course had started from 14th Sept 2015 and will go a 4-week program. Anyone can join this course before closing the program, provided s/he should clear all the criteria to get Certificate or otherwise, can continue to earn knowledge. The course also giving the option to get a digital signature certificate after completion of the course, on paying the charging amount of money.

In the next few weeks, I will be posting a summary on the current ongoing course, and this will contain the topics covered, study materials and references. 

Arif Ahmed

Android (Operating System) – An Overview

Introduction

Android is a smartphone operating system build above the Linux Kernel and developed by Google. Applications in android OS are run in Dalvik virtual machine, a kind of VM similar to JVM for JAVA. The source code of the OS is written in C, C++ and JAVA and periodically released under Open Source GNU Licensed by Google. The latest version is "Lollipop" API Level 5.1 released on April 21, 2015. Other mobile manufacturers ship their product integrating custom application to the original version.

A quick glance on Android Versions and release date

Android Version	API Level	Released Date
Android 5.0 Lollipop	API level 21	November 12, 2014
Android 4.4 KitKat	API level 19	October 31, 2013
Android 4.1 Jelly Bean	API level 16	July 9, 2012
Android 4.0 Ice Cream Sandwich	API level 14	October 19, 2011
Android 3.0 Honeycomb	API level 11	February 22, 2011
Android 2.3 Gingerbread	API level 9	December 6, 2010
Android 2.2  Froyo	API level 8	May 20, 2010
Android 2.0 Eclair	API level 5	October 26, 2009
Android 1.6 Donut	API level 4	September 15, 2009
Android 1.5	API level 3	April 27, 2009
Android 1.1	API level 2	February 9, 2009
Android 1.0	API level 1	September 23, 2008

As the popularity of this OS grows because of the open source and interactive interface, it has been released for other hardware devices particularly Android TV(for televisions), Android Wear(for wearable device  smartwatch), Android Car(for vehicle). According to Google, in 2014 this OS has total 1 billion active users per month. Earlier it was 538 million in 2013.  According to the latest statistics, smartphone user’s distribution based on the OS is like this.

Android OS Architecture

Android OS architecture is a stack of software components, each correlate with one another. It is like TCP/IP networking protocol stack, when a task is performed, different components of the layers are interact to accomplish the task.

The list of layer from Bottom to top is:

1. Linux Kernel

2. Android Libraries & Android Runtime

3. Application Framework and

4. Applications

Linux Kernel:

Android OS is built on the top of Linux Kernel.  Kernel is the critical component of an OS that performs management of input/output requests from the various softwares. It is the bridge between the hardware & software, and  all the system calls are handled by kernel.  Android OS are built above the Linux Kernel 2.6 with little modification by the Google. As we have told, Kernel are responsible for handling I/O request, most of the device drivers resides in this layer. When the OS is boot, the critical codes of the kernel are loaded in the protected area, it help in preventing any kind of code modification by the low-level software.

Libraries:

Android Libraries are native libraries used by the developers during the Android application development. They are in the top of the Linux Kernel. There are many libraries, each is dedicated for a particular goal. For example, WebKit is specifically for handling the browsing internet web, SQLite is database system and Media Framework is to play different audio, video media files etc.

Android Runtime :

Android runtime resides on the top of the Linux Kernel, parallel with Libraries.   It contains core libraries and Dalvik Virtual Machine (DVM). DVM is a Virtual Machine (VM) responsible for running the Android applications, just like JVM to run the java application. But, unlike JVM, it is in optimized and takes less memory to run an application. The use of DVM provides high performance.

Application Framework

Application Framework contains popular services that are implemented in java classes. Android developers frequently invoke these services, when an application is developed. Each service is created for specific purpose. Some of the notable applications framework with the usability is:

1. Activity Manager – The service Controls state of the application lifecycle and activity stack.

2. Content Providers – It Allows applications to publish and share data with other applications. This is a kind IPC.

3. Resource Manager − It Provides access to non-code embedded resources such as strings, color settings and user interface layouts.

4. Notifications Manager – Notification manager send applications to notify any alerts and show to the user.

5. View System – View System is especially for User Interface.

Applications

The top layer in the Android Software stack is Application Layer. It contains all the applications installed in the OS. Some of the example are : Home, Contacts, Call Log, VLC Payer, User defined applications etc. 

Selfie with my Friends

 Purbankan(PD), Me(Arif) and  Nikumani (From Left)

Purbankan(PD), Me(Arif) and  Nikumani (From Left)

Purbankan(PD), Me(Arif) and  Nikumani (From Left)

How to set proxy in Ubuntu using Command Line Interface(CLI)?

Servers such as Ubuntu Server, Fedora Server, VM based servers etc. run without GUI. If the edge of the network requires proxy connection to establish Internet, it has to be done from the CLI. Here are the basic commands to set proxy for Ubuntu.

1. To Check whether proxy is already set:

$echo $http_proxy   (For http proxy)
$echo $https_proxy  (For https proxy)
$echo $ftp_proxy    (For ftp proxy)

2. To set proxy:

$export http_proxy="http://proxyuser:proxypwd@proxy.server.com:port_number/"
$export https_proxy="https://proxyuser:proxypwd@proxy.server.com:port_number/"
$export ftp_proxy="ftp://proxyuser:proxypwd@proxy.server.com:port_number/"

    change proxyuser to your proxy user
    change proxypwd to your proxy password
    change proxy.server.com to the URL of your proxy server
    change port_number to the proxy port configured on your proxy server


Note:

Ubuntu command apt-get does not work after the above setting also. For this, the following steps have to follow:

1. Create a file name 40proxy inside /etc/apt/apt.conf.d/
2. write the following lines(according to the requirement) :

Acquire::http::proxy "http://proxyuser:proxypwd@proxy.server.com:port_number/";
Acquire::https::proxy "https://proxyuser:proxypwd@proxy.server.com:port_number/";
Acquire::ftp::proxy "ftp://proxyuser:proxypwd@proxy.server.com:port_number/";

Set Proxy in Git Application

Git is a free and open source distributed version control system designed to handle everything from small to very large projects with speed and efficiency. Any Git user can upload projects source code to the Git server and share with others. It also allows users to update and synchronous from the local machine. Generally, Git comes with Command Line Interface(CLI) exceptionally few 3rd party GUI applications. 

Git does not use normal system proxy and to connect, proxy has to be explicitly set for this application. If you are trying to connect Github from behind the proxy server, it will not work unless the proxy is set.

How to set proxy from the CLI? Here are the few steps :

1.Check whether proxy is set  :

git config --global --get http.proxy
git config --global --get https.proxy

2. Set proxy :

git config --global http.proxy http://proxyuser:proxypwd@proxy.server.com:8080
git config --global https.proxy https://proxyuser:proxypwd@proxy.server.com:8080

    change proxyuser to your proxy user
    change proxypwd to your proxy password
    change proxy.server.com to the URL of your proxy server
    change 8080 to the proxy port configured on your proxy server

3. To reset this proxy and work without (no proxy):

git config --global --unset http.proxy
git config --global --unset https.proxy

Current Position

Hi,

I am currently working as an Assistant Professor (Contractual) at Computer Science & Engineering department, NIT Silchar. NIT Silchar is one of 30 NITs under the Government of India(GoI) and It has been designated as Institute of National Importance(INI) under the National Institutes of Technology Act, 2007.

However in parallel with teaching, my ongoing research field are Mobile Cloud Computing, Software Defined Networking.

-Arif

Introduction

Hi Everyone,

I am Arif Ahmed, INDIAN, from Silchar, Assam. I completed graduation(Information technology) from Assam University, INDIA in 2012, and post graduation(Computer Science & Engineering) from National Institute of Technology, Silchar in 2014.

Here, I will post ideas related to my activities i.e. Research, Teaching etc.

Cheers,
Arif