LINUX:In 1969 AT&T made a decision to withdraw Multics and go with GECOS (General Electric Comprehensive Operating Supervisor / System), with AT & T in Bells Lab when Multics was withdrawn some of the programmers named Ken Thompson and Dennis Ritchie decided to rewrite operating system in order to support low cost computer..To Know More



    MICROSOFT:Microsoft was established to develop and sell BASIC interpreters for the Altair 8800. It rose to dominate the home computer operating system market with MS-DOS in the mid-1980s,followed by the Microsoft Windows line of operating systems. To Know More



    CISCO:During the early 1980s, there was a married couple namely Len and Sandy Bosack who used to work in two different departments of computer located in Stanford University. This couple was facing problem in making their computers communicate with each other To Know More



10 things about IPv6 addressing

1: IPv6 addresses are 128-bit hexadecimal numbers

The IPv4 addresses we are all used to seeing are made up of four numerical octets that combine to form a 32-bit address. IPv6 addresses look nothing like IPv4 addresses. IPv6 addresses are 128 bits in length and are made up of hexadecimal characters.
In IPv4, each octet consists of a decimal number ranging from 0 to 255. These numbers are typically separated by periods. In IPv6, addresses are expressed as a series of eight 4-character hexadecimal numbers, which represent 16 bits each (for a total of 128 bits). As we’ll see in a minute, IPv6 addresses can sometimes be abbreviated in a way that allows them to be expressed with fewer characters.

2: Link local unicast addresses are easy to identify

IPv6 reserves certain headers for different types of addresses. Probably the best known example of this is that link local unicast addresses always begin with FE80. Similarly, multicast addresses always begin with FF0x, where the x is a placeholder representing a number from 1 to 8.

3: Leading zeros are suppressed

Because of their long bit lengths, IPv6 addresses tend to contain a lot of zeros. When a section of an address starts with one or more zeros, those zeros are nothing more than placeholders. So any leading zeros can be suppressed. To get a better idea of what I mean, look at this address:
If this were a real address, any leading zero within a section could be suppressed. The result would look like this:
As you can see, suppressing leading zeros goes a long way toward shortening the address.

4: Inline zeros can sometimes be suppressed

Real IPv6 addresses tend to contain long sections of nothing but zeros, which can also be suppressed. For example, consider the address shown below:
In this address, there are four sequential sections separated by zeros. Rather than simply suppressing the leading zeros, you can get rid of all of the sequential zeros and replace them with two colons. The two colons tell the operating system that everything in between them is a zero. The address shown above then becomes:
You must remember two things about inline zero suppression. First, you can suppress a section only if it contains nothing but zeros. For example, you will notice that the second part of the address shown above still contains some trailing zeros. Those zeros were retained because there are non-zero characters in the section. Second, you can use the double colon notation only once in any given address.

5: Loopback addresses don’t even look like addresses

In IPv4, a designated address known as a loopback address points to the local machine. The loopback address for any IPv4-enabled device is
Like IPv4, there is also a designated loopback address for IPv6:
Once all of the zeros have been suppressed, however, the IPv6 loopback address doesn’t even look like a valid address. The loopback address is usually expressed as ::1.

6: You don’t need a traditional subnet mask

In IPv4, every IP address comes with a corresponding subnet mask. IPv6 also uses subnets, but the subnet ID is built into the address.
In an IPv6 address, the first 48 bits are the network prefix. The next 16 bits are the subnet ID and are used for defining subnets. The last 64 bits are the interface identifier (which is also known as the Interface ID or the Device ID).
If necessary, the bits that are normally reserved for the Device ID can be used for additional subnet masking. However, this is normally not necessary, as using a 16-bit subnet and a 64-bit device ID provides for 65,535 subnets with quintillions of possible device IDs per subnet. Still, some organizations are already going beyond 16-bit subnet IDs.

7: DNS is still a valid technology

In IPv4, Host (A) records are used to map an IP address to a host name. DNS is still used in IPv6, but Host (A) records are not used by IPv6 addresses. Instead, IPv6 uses AAAA resource records, which are sometimes referred to as Quad A records. The domain is used for reverse hostname resolution.

8: IPv6 can tunnel its way across IPv4 networks

One of the things that has caused IPv6 adoption to take so long is that IPv6 is not generally compatible with IPv4 networks. As a result, a number of transition technologies use tunneling to facilitate cross network compatibility. Two such technologies are Teredo and 6to4. Although these technologies work in different ways, the basic idea is that both encapsulate IPv6 packets inside IPv4 packets. That way, IPv6 traffic can flow across an IPv4 network. Keep in mind, however, that tunnel endpoints are required on both ends to encapsulate and extract the IPv6 packets.

9: You might already be using IPv6

Beginning with Windows Vista, Microsoft began installing and enabling IPv6 by default. Because the Windows implementation of IPv6 is self-configuring, your computers could be broadcasting IPv6 traffic without your even knowing it. Of course, this doesn’t necessarily mean that you can abandon IPv4. Not all switches and routers support IPv6, just as some applications contain hard-coded references to IPv4 addresses.

10: Windows doesn’t fully support IPv6

It’s kind of ironic, but as hard as Microsoft has been pushing IPv6 adoption, Windows does not fully support IPv6 in all the ways you might expect. For example, in Windows, it is possible to include an IP address within a Universal Naming Convention (\\\C$, for example). However, you can’t do this with IPv6 addresses because when Windows sees a colon, it assumes you’re referencing a drive letter.
To work around this issue, Microsoft has established a special domain for IPv6 address translation. If you want to include an IPv6 address within a Universal Naming Convention, you must replace the colons with dashes and append to the end of the address — for example, FE80-AB00–

Linux File Systems: Ext2 vs Ext3 vs Ext4


  • Ext2 stands for second extended file system.
  • It was introduced in 1993. Developed by Rémy Card.
  • This was developed to overcome the limitation of the original ext file system.
  • Ext2 does not have journaling feature.
  • On flash drives, usb drives, ext2 is recommended, as it doesn’t need to do the over head of journaling.
  • Maximum individual file size can be from 16 GB to 2 TB
  • Overall ext2 file system size can be from 2 TB to 32 TB


  • Ext3 stands for third extended file system.
  • It was introduced in 2001. Developed by Stephen Tweedie.
  • Starting from Linux Kernel 2.4.15 ext3 was available.
  • The main benefit of ext3 is that it allows journaling.
  • Journaling has a dedicated area in the file system, where all the changes are tracked. When the system crashes, the possibility of file system corruption is less because of journaling.
  • Maximum individual file size can be from 16 GB to 2 TB
  • Overall ext3 file system size can be from 2 TB to 32 TB
  • There are three types of journaling available in ext3 file system.
    • Journal – Metadata and content are saved in the journal.
    • Ordered – Only metadata is saved in the journal. Metadata are journaled only after writing the content to disk. This is the default.
    • Writeback – Only metadata is saved in the journal. Metadata might be journaled either before or after the content is written to the disk.
  • You can convert a ext2 file system to ext3 file system directly (without backup/restore).


  • Ext4 stands for fourth extended file system.
  • It was introduced in 2008.
  • Starting from Linux Kernel 2.6.19 ext4 was available.
  • Supports huge individual file size and overall file system size.
  • Maximum individual file size can be from 16 GB to 16 TB
  • Overall maximum ext4 file system size is 1 EB (exabyte). 1 EB = 1024 PB (petabyte). 1 PB = 1024 TB (terabyte).
  • Directory can contain a maximum of 64,000 subdirectories (as opposed to 32,000 in ext3)
  • You can also mount an existing ext3 fs as ext4 fs (without having to upgrade it).
  • Several other new features are introduced in ext4: multiblock allocation, delayed allocation, journal checksum. fast fsck, etc. All you need to know is that these new features have improved the performance and reliability of the filesystem when compared to ext3.
  • In ext4, you also have the option of turning the journaling feature “off”.

Calculation I. P Address

Calculation I. P Address

Class C
                                           till to
                                             254 Usable ID
In Class there is 2 Host. If you want to calculate 2 host. You can calculate this way
           *      256
Answer :65536  -  2
Answer :65534
There is two type of I P  Address
Public I. P Address
PVT I.P Address
Public I.P address you to purchase for internets


Conversion Chart

Conversion Chart

Binary to Decimal

29 =    512 You can Continue 
but we using till 20 = 1   to   28=   256
Question:1 0 0 1 1 1 0 1 0

Always count from last figure
See Chart and Calculate
      +         2
Total:  314 Dec
Question    1  0  1  1  1

                    +       1
                        Total :     23 Dec
Decimal to Binary
Question  :  329
You have to see in which figure you can minus 329. Please see the chart in which figure you can minus.
Ans  :As per the Chart you can minus from 256
                                                            __        256
                                                            __        64
                                                            __        8
Ans :  101001001 Binary
Question  :  200
You have to see in which figure you can minus 200. Please see the chart in which figure you can minus.
Ans  :  As per the Chart you can minus from  128
                                                            __        128
                                                            __        64
                                                            __        8
Ans :  11001000 Binary
You have to go end till 20


What is Network ?

Network is a connected collection of device and end point  systems, such as computer’s and Server’s which can communicate with each other.

Common Physical Components of Network

1.      PC

2.      Inter connections

3.      Switches

4.      Routers

5.      WLAN


P C   :  The computer serve as a end point in the network that they send and received the Data.


Inter Connection  :  Inter connection  Consist of Components that provide a means for data to travel from one point to another point in the network. This category include component such as following


A.  NIC:    that Translate computer data into a format that can transmit over the network.

B.  Network Media:  Such as cable or Wireless Media that provide the means by which the signal are transmitted from one network device to another.


C. Connector:that provides the connection point for the media.


Switches:  Switches are the device that provides networks attachment to the end systems and intelligence switching of the data within the local network.



Routers:Routers interconnect networks and chose the best part between networks.



WLAN:  Wireless LAN device:  WLAN device connect network device computers and other end pint to the network without cable. The minimum requirement for the wireless access to the network is an end point with WLAN, NIC and an access point that connect through the wire network.



Resource Sharing function and benefit


1.      Data and Application

2.      Resources

3.      Network Storage

4.      Backup devices



Network User Application:-


1.      Email

2.      Web Browser

3.      Instant Messaging

4.      Collaboration

5.      Data base

6.      Mobile Phone data Application

7.      Peer to Peer

8.      Online gaming



Characteristic of Network


1.      Speed:  Speed is a major of hoe fast data is transmitted over the network a more term precious data rate.

2.      Cost: Cost indicates the general expanse of component, installation and maintenance of network.

3.      Security:  Security indicates how to protect the network is including information that is transmitted over the network.

4.      Availability:  is a major of Probability that the network will be available for use when it is required.

5.      Scalability:  Scalability indicates how well the network can accommodate more uses and data transmission requirement.

6.      Reliability:  Reliability indicates the dependability of the Components that make up the network, such as Routers, Switches and PC. Reliability is a often major as a probability of failure or means time between failure.

7.      Topology: In Network there are physical and logical topology.


A.     Physical Topology:  is the arrangement of the cable, network devices and end System.

B.      Logical Topology:  is the part that data signal takes through physical topology.



I.P Address

I.P:  Internet Protocol

Protocol:  Protocol is the set of rules which define communication over the network.


Two types of Protocol

1.      Vendor Specific --------IIPX/SPX, Apple talk(Novel)

2.      Open Standard -------- TCP/IP ---(ieee Invent)

Vendor Specific .

          Windows                                                          Linux
8bits = 1 octets =1bytes
1024 Bytes  ----1 KB
1024  KB      -----  1MB
1024 MB      -----  1GB
1024 GB       ------ 1TB
1024 TB      ------- 1 PB
AClass  ===   1---- 126    127  =  Loop Back Reserve
B Class  ===   128----191
C Class  ===   192----223
D Class  ===   224 ----239
E Class  ===   240 ----255 Reserved   I. P for Loop Back
 We are using only A, B, C Class
D Class:   Using Multi Casting
E Class :  Reserve for  Research  and Development
                          N   H   H   H
Class A   :
                        255.0. 0. 0
  N    N   H   H
Class B   :
                         255.255. 0. 0
  N    N    N   H
Class C   :          200. 10.50.50
                        255.255. 255. 0


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