Showing posts with label Electronics. Show all posts
Showing posts with label Electronics. Show all posts

## Basics of Sub-netting

Posted by Tushar Bedekar

### What is Subnetting?

Subnetting allows you to create multiple logical networks that exist within a single Class A, B, or C network.
To subnet a network is to create logical divisions of the network. Subnetting, therefore, involves dividing the network into smaller portions called subnets. Subnetting applies to IP addresses because this is done by borrowing bits from the host portion of the IP address. In a sense, the IP address then has three components - the network part, the subnet part and, finally, the host part.
For Example:
11111111.11111111.11111111.11110000 will be equal to 255.255.255.240 in decimal.
Where, 11111111 = 255
And, 11110000 = 240
In 11111111 the total bits in network field are 8. So, 2^8=255   and,

For 11110000, Notice that the fourth byte in the network mask has four bits set to ‘1’. If you look at the chart below, its value is 240 (128+64+32+16).
There are so many reasons why we subnet:
a. It helps in the preservation of address space in other not to waste addresses.
b. It used for security.

c. It helps to control network traffic due to collisions of packets transmitted by other node (host) on the same segment.

In order to subnet a network address, The  subnet mask has to be extended, using some of the bits from the host ID portion of the address to create a sub network ID.

### How to Subnet:

This mean, borrow some bits from the host part to add to the network part. This allows us to have more networks than using the default subnet mask. For example, we can borrow some bits in the next octet to make the address belong to a different network.
For example:
Now you can clearly see that the subnet mask will decide which is the network part, which is the Host part. By borrowing 8 bits, our subnet mask will be like this:
After changing the second octet of the subnet mask from all “0″ to all “1″, the Network part is now extended. Now we can create new networks by changing number in the first or second octet. This greatly increases the number of networks we can create.
So, in conclusion we “subnet” by borrowing bit “0″ in the Host portion and converting them to bit “1″. The number of borrowed bits is depended on how many networks we need.
For Example:
Calculating Host: 11111111.11111111.11111111.11110000 will be equal 14 hosts
Notice the last four bits of the network mass has set to 0,
Formula = 2^4=16, and out of 16 we have only 14 valid hosts.
16-2=14 hosts, we have subtracted 2 because it is used for broadcast and network ID in the network.
Below is a quick reminder of the two major rules governing the number of subnet valid host addresses available given the particular network mas length.
1. Number of Available Subnet Cheat Sheet
Where “S” = Number of Subnet bits
2. Number of Available Valid Host Addresses Cheat Sheet
Where “h” = Number of host bits
3. Binary/Decimal/Subnet Cheat Sheet.

## How A Software Actually Works On A Hardware

Posted by Tushar Bedekar
Hi,Today We are going to discuss a new topic which may be very old but important one, also a big question in front of  us.

### What is a Program me?

As we all know that a program me is a group of instruction which is needed to be executed by the machine like a computer to perform a certain task.but the biggest question is that how these group instruction are executed on the hardware to perform a assigned task.Basically these instructions which are being executed are itself a group of micro instruction an microcode.which are executed on any machine to execute a one particular instruction. now,

### what is programming?

Actually the programming is nothing but Def:- provide (a computer or other machine) with coded instructions for the automatic performance of a task.But This definition does not gives the full idea about what actually the programming is? and also it does not gives the idea about how the software runs on the hardware.

As we all have listened about PLA`s(programmable array logic), PAL`s (programmable logical array) and also about FPLA (field programmable logical array).Basically these are the logical devices consisting of arrays of AND & OR gates and also other different supporting devices.These devices may be Hardwired or may be re-programmable.

### How To program me these devices?

Basically devices consist of programmable AND & OR gates.That these arrays consist of fussing and re fussing technology.These fuses may be burned and or lay intact as per the requirement.This fussing can be done generally by supplying a sufficient amount of current through the fuse.

### Types of fuses:-

• Metallic Fuses.
• Diode/Transistors fuses
• Silicon Fuses.Etc
So by fussing the different fuses the programming can be done.

### Publisher's Last Words:

• I hope you have got answers of some Questions by this small post and I know you have lot of questions, So please feel free to ask in comment section or you can mail me my    e mail id is : tushar.bedekar11@gmail.com
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## What is Bandwidth ?

Posted by Tushar Bedekar
This is most confusing topic for most of the electronics engineers today.But it is a most important topic because it is one basic topic for the communication engineering.so i find this topic to write first while writing my first topic on electronics engineering.

### Introduction:-

According to me following are the different definition of the bandwidth:-

•  The range of the frequencies that can be passed without any attenuation through any communication devices.
• The portion of electromagnetic spectrum that is being occupied by the signal.
• Signal is a physical quantity which consist of some information and which is the function of one or more independent variables.
• Bandwidth as Difference between upper and lower limit of the signal.
• let F1=50 Hz  & F2=80 Hz Band width =30 Hz (F2-F1)
But as per the above definition`s about the bandwidth it does not give that much of information that we require to understand the topic in detail.

• The Internet consists of tens of millions of computers throughout the world, all connected by cables. Your ISP (Internet Service Provider) is a company that has a very high-speed (and very expensive) connection to the Internet. Your ISP makes its money by renting little "chunks" of that high-speed connection to consumers who don't want to spend thousands of dollars each month for an Internet connection.
If you've ever wondered why it takes so long to download certain Web pages or other files to your computer, it's all determined by the bandwidth of the connection between your computer and your Internet Service Provider. Which is to say, it all hinges on that wire connecting your computer to your modem to your ISP. That connection is often referred to as the last mile, as illustrated in Figure 1.
When you open a Web page or download a file, it travels very quickly from wherever it happens to be on the planet Earth to your ISP. It then travels from the ISP's computers to your computer. The actual speed at which information moves through a wire is always the same, no matter what your bandwidth might be. That is, electrons run through the wires at close to the speed of light, about  670,000,000 MPH (six hundred and seventy million miles per hour). At that speed, you could circle the globe 7 times a second, or 420 times a minute. So why does it take so long for every Web page you visit to appear on your screen? That's where bandwidth comes in.
Bandwidth is easy to understand if we use an analogy from everyday life. Imagine that instead of trying to get a Web page or file from your ISP through wires, you're trying to drain a swimming pool. The water in the pool is the Web page or file. If you stick a skinny hose to drain the water from the pool, as in Figure 2, it will take quite a while to drain all the water.
Figure 1
Now let's say that instead of sticking a skinny pipe onto the pool we put on a big fat pipe, as in Figure 3. I don’t think it takes a physics major to realize that it’s going to take less time to drain the pool in Figure 3 than it is to drain the pool in Figure 2.

Figure 2
We can say that the fat drain pipe in Figure 3 is "wider" than the pipe in Figure 2. Or, we could take it another step and say that the fat pipe in Figure 3 has more bandwidth than the skinny pipe. And ultimately, that's what bandwidth is all about. How much stuff can pass through the pipe (or wire) at a time.
Dial-up Internet accounts, which use a standard telephone line to connect to an ISP, have a very narrow bandwidth (about 50 Kbps or 50,000 bits per second). Thus, things are slow in the sense that it takes a long time to download things.
broadband Internet account can move data at anywhere from 128 Kbps to 2,000 Kbps or more. That's like the fat drain pipe. It takes a lot less time to get a Web page or file from your ISP's computer to your computer using the broadband account than it does the dial-up account.
So the whole bandwidth thing (like many things "computerish") boils down to a time vs. money decision. You can either spend the extra amount per month for a faster connection, and spend less time waiting for things to download. Or, you spend less money on a dial-up account, but spend more time waiting for things to appear on your screen.