OSI Model (Open System Interconnection model)
OSI model
I will discuss here a very essential and interesting topic, it is the step one in the networking world
you can imagine the OSI model like a stair you should use to go anywhere from your home so you need to take it step by step from above to the bottom when you are going and from bottom to above when you are arriving
So when you are surfing the internet using whatever browser, then you typed the url www.google.com actually from this point while approaching the internet, you have entered the the stack and you are now in the interfacing layer which is the Application layer, here your browser or whatever interface connect you to the network, Ex. HTTP, FTP, SMTP
As you know computer network speak just like us, but with a different language so at this point you need a translator so Presentation layer does the translation and mapping, also presentation layer do data compression and encryption for the data stream Ex. ASCII, JPEG
At this point you are ready to create a session with google server and Session layer is here for duty, managing and maintaining the session and controlling the dialog
Transport Layer plays important rule to ensure your data sequence transferring and determine the connection type if its connection oriented TCP or connection less UDP
Transport layer ensures reliability of data received by destination through flow control segmentation /desegmentataion and error control and application identification through a port number
Now we came to the point which we are done with the user stuff and start doing some network related procedures to ensure that your data will be sent to wherever you want correctly, this is like sending postal mail and we just finished writing the letter so the logical next step is to put it inside an envelope, write some identification data for the post office to know the destination of this letter and obviously it should have also your local address so that the receive person will know it was from you.
Network Layer here where we put our addresses on the envelope these addresses will never be changed through the transferring of the mail (packet) to the destination, this layer provides logical addressing by the IP protocol also it determine the shortest path (route) for the mail (packet) to reach its destination Ex. ipv4 ,ipv6, ipsec
DataLink Layer now you done all your work, but for the post office to send this envelope it might not be one flight or one way it might travel through many other post offices in between to reach its destination, so when this mail travel to the next station on the its way we will use the post office address (physical address) of both the sending post office and the received post office as source and destination address's then when it reach the destination post office it will check for the logical destination address if it is in his zone so it will call the person you send this mail to and he will receive it and we are done, but if not in his zone ,current post office will see what the next station in the journey and put its own address as the source address and put the address of the next receiving post office as the new destination post office, will it goes on and on like this till it reach post office which have the logical address (address you have put yourself in the envelope of the letter ) and call the guy deliver it to him and we are done
so in another word DataLink Layer provides physical addressing also do framing for the packet received by Network layer Ex. Ethernet protocol, PPP
DataLink layer consists of two sub layer
Media Access Control (MAC) layer - responsible for controlling how devices in a network gain access to data and permission to transmit it.
Logical link control (LLC) layer - controls error checking and packet synchronization.
Finally we should think about method post office will use to travel this mail to the other offices it may use airplane may be ship in the sea may be by train it could be also delivered by delivery guy ... so the physical method it will be used is recognized in the Physical Layer
Physical Layer provide electrical signal and physical media specification for data connection
Ex. DSL, ISDN , USB
So OSI model is so important as it is the based for everything your would lean in the networking field
At the end I wish I have delivered good information to you and i would thank you for reading this article
I will discuss here a very essential and interesting topic, it is the step one in the networking world
you can imagine the OSI model like a stair you should use to go anywhere from your home so you need to take it step by step from above to the bottom when you are going and from bottom to above when you are arriving
So when you are surfing the internet using whatever browser, then you typed the url www.google.com actually from this point while approaching the internet, you have entered the the stack and you are now in the interfacing layer which is the Application layer, here your browser or whatever interface connect you to the network, Ex. HTTP, FTP, SMTP
As you know computer network speak just like us, but with a different language so at this point you need a translator so Presentation layer does the translation and mapping, also presentation layer do data compression and encryption for the data stream Ex. ASCII, JPEG
At this point you are ready to create a session with google server and Session layer is here for duty, managing and maintaining the session and controlling the dialog
Transport Layer plays important rule to ensure your data sequence transferring and determine the connection type if its connection oriented TCP or connection less UDP
Transport layer ensures reliability of data received by destination through flow control segmentation /desegmentataion and error control and application identification through a port number
Now we came to the point which we are done with the user stuff and start doing some network related procedures to ensure that your data will be sent to wherever you want correctly, this is like sending postal mail and we just finished writing the letter so the logical next step is to put it inside an envelope, write some identification data for the post office to know the destination of this letter and obviously it should have also your local address so that the receive person will know it was from you.
Network Layer here where we put our addresses on the envelope these addresses will never be changed through the transferring of the mail (packet) to the destination, this layer provides logical addressing by the IP protocol also it determine the shortest path (route) for the mail (packet) to reach its destination Ex. ipv4 ,ipv6, ipsec
DataLink Layer now you done all your work, but for the post office to send this envelope it might not be one flight or one way it might travel through many other post offices in between to reach its destination, so when this mail travel to the next station on the its way we will use the post office address (physical address) of both the sending post office and the received post office as source and destination address's then when it reach the destination post office it will check for the logical destination address if it is in his zone so it will call the person you send this mail to and he will receive it and we are done, but if not in his zone ,current post office will see what the next station in the journey and put its own address as the source address and put the address of the next receiving post office as the new destination post office, will it goes on and on like this till it reach post office which have the logical address (address you have put yourself in the envelope of the letter ) and call the guy deliver it to him and we are done
so in another word DataLink Layer provides physical addressing also do framing for the packet received by Network layer Ex. Ethernet protocol, PPP
DataLink layer consists of two sub layer
Media Access Control (MAC) layer - responsible for controlling how devices in a network gain access to data and permission to transmit it.
Logical link control (LLC) layer - controls error checking and packet synchronization.
Finally we should think about method post office will use to travel this mail to the other offices it may use airplane may be ship in the sea may be by train it could be also delivered by delivery guy ... so the physical method it will be used is recognized in the Physical Layer
Physical Layer provide electrical signal and physical media specification for data connection
Ex. DSL, ISDN , USB
So OSI model is so important as it is the based for everything your would lean in the networking field
At the end I wish I have delivered good information to you and i would thank you for reading this article
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