Computer Network Freaks

How does torrent works?

Most of Software's,movies,videos e.t.c are downloaded with the help of torrents but do you know the technology behind it? How does torrent work? It is an wonderful and my favourite networking technology called peer to peer connection.

In this Technology the users(we) do not download content from a server,but we download the content from another user that is downloading the same file.

There are two basic terms before understanding how does torrent works and they are:-
peer:-He is the one who download the content
seed:-He is the one who upload the content

Remember that you can be a peer to another user while a seed to another.


Now,I think you would probably have a question that how can we download a content from a user who is currently downloading a file and does not have whole file.

There should be one seed peer who has whole content and seeds it to keep torrent running.

 Let me give explanation with the help of an example:-

Suppose there are three users A,B and C and a file networks.mp4. This file contents are divided into 6 blocks 1,2,3,4,5,6. Now if initially user A is seed and B has downloaded block 1 and 2 while user C has downloaded  5 and 6. Ok?? Got this thing?? This was just the initially condition,the crux is yet to come.

Now user B will say to user C that you give me block 5 and 6.User C would upload it to B only if he gets something.Here it is block no 1 and 2. If user C has nothing to download from user B he will not upload it simple.

So user B downloads 5 and 6 while uploads 1 and 2 and user C vice versa.

I question would probably arise:

What if there is no one downloading the content at present time?? Where he will get the data??

So the answer is the seed peer who does download anything but seeds its contents so as to keep a torrent running.If there is no seed peer,the torrent would fail.

So this was the concept to the generally asked question how does torrent works? Hope you found it usefull.

Ever wondered how Bandwidth is shared on a link in a network?

The two core methods are TDM and FDM. TDM stands for Time Division Multiplexing. FDM stands for Frequency Division Multiplexing.



Time Division Multiplexing(TDM):-
Here bandwidth is shared with respect to time i.e whole of bandwidth is given to a computer for some specific interval of time.

Frequency Division Multiplexing(FDM).
Here Bandwidth is shared with respect to frequency ie if two computer are connected on a shared link,each computer will get half of the total bandwidth.


Let us take an example:-
Suppose there are two computer connected on a shared link of bandwidth 1Mbps.

Now if we use TDM each user will get the full 1Mbps bandwidth for 1sec(just for example). i.e If computer A gets 1 Mbps for 1 sec,computer B will get that bandwidth for the next 1 sec

Now if we use FDM,the links bandwidth will get shared i.e each computer will use 500 kbps bandwidth.

The methods explained above is not the one implemented in current technologies but is basis of understanding the current technologies.

Okay so I hope you People have some knowledge about layers in Networks.You can take a look here Layers in Computer Networks. Now, I will go from higher layer to lower layer. At Application layer the data is send by the client to lower layer i.e Transport layer. Transport layer divided the data into Segments or Datagrams. There are two protocols of Transport layer and they are UDP and TCP. TCP divides data into Segments whereas UDP divides data into Datagrams.

Now it goes at Network layer. At Network layer the unit becomes Packets.The network layer adds IP address to it and now we call it a Packets.

Now when it reaches the datalink layer,the layer adds physical address and now the last step would be to send it to physical layer so that it can be converter to bits and then modulate them and send them as signals but to allow receiver to know which bits came first we divide the data into frames at datalink layer. So at datalink layer we usually say frames and it is one of the important function of link layer that we call framing.

So in short:-
At Transport layer - Segments or Datagrams
At Network layer - Packets
At Datalink layer - frames

This was the Difference between Segments,Packets and Frames. If you have any queries please let me know.

Why we need layers in computer networks???

I always wondered,why we need layers in computer networks???
We have heard about the layers like Link layer,Network layer,Transport layer,Application layer but why???

• Application layer - User Interface in networking will be taken care by it
• Transport layer - Takes Responsibility of communicating to a specific process in a computer connected in the Network
• Network layer - Takes Responsibility of Routing
• Link Layer - Takes Responsibility of delivering message to specific computer in a Network
• Physical layer - Takes Responsibility of converting data into bits and sending them through a wire.

Saw?? How our life is easy?? We divided Tasks and each layer is responsible for its task.