è Take and example of 5 computers.If we connect 4 computers with one another with the ethernet cable,and if few computers are doing data transfer with each other some are of doing http transfer to each other.Some are accessing their emails and so on.All are doing this things simultenously.
è So the question comes to everyone’s mind is that “ why they are not collide with each other ? ”
è I am going to focus in that what exactly the technique or the procedure used by the ethernet,so that collision is not occuring while the data transfer.
Why to have access control ?
Why to have access control ?
è To avoid collision.
è Take and example of traffic signals.There are green yellow and red lights are there.They have defined some rules of the traffic so that accidents/collision of the vehicles should not be occur.In the case of there are no rules then one or the more car will be fall in accidents.
è Take and example of traffic signals.There are green yellow and red lights are there.They have defined some rules of the traffic so that accidents/collision of the vehicles should not be occur.In the case of there are no rules then one or the more car will be fall in accidents.
è So in the case of avoiding this type of collision there should be some rules or the protocols in the system by the computer accessing the internet or the accession the LAN.
è Access Control also helps in the case of collision occurs.There should be collision revovery process in there if collision occurs.
Why exactly the collision occurs ?
è One or mode node are start transferring while others are going on.
è Two or mode nodes are start transmission at the same time.
How computer will come to know that the collision has been occurred in the system or not ?
è To understand the answer of this question we have to understand first that “ What is packets ? ”
1. Packets are nothing but the voltage and the current electric signals.
2. So if the packets are transferred,some voltage is flowing and current also in the ethernet.
3. So if the system has been found that the current electric signals and the volatage is high compare to the default level,it will come to know that the collision has been occurred.
What is Access Control Protocol ? -> Mechanism To Avoid the Collision.
è This has some rules which detects and prevent the collisions.
1. It has an ability to find out the busy medium.So if some new packets came then it wont allow it to transfer through that busy medium.
2. It will wait until that medium becomes free and then will allow packets to transfer through that medium.
3. In the case of rule 1 and 2 are not obeyed then there should be some technique/way which can find/detect the collison.
4. After first collision occures the transmitting nodes should act in such a way that it reduces the chances of the more collisions.
è If this 4 rules are obeyd then no collision can take place into the system and even if it takes place we can recover from it.
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