I was reading a pdf note from cisco website (Preparing to take CCNA exam) and find this out.
The question is attached (question.jpg) and the answer which was given too.
befor you open them : Do Late collision happen before this 64 bytes are transmitted ? or after?
In the topic some explaination are shown and we have to drag and drop each explaination in the matching case either routine collisions or late collisions.
Then they match the explaination "Before this 64 bytes are transmitted" to Late collision .
I was always thinking that Late collisions (THEY HAPPEN LATER) happen after 64 bytes transmitted on the media by its sender
You are absolutely right. To allow collision detection to work properly, the period in which collisions are detected is restricted (512 bit-times).
For Ethernet, this is 51.2us (microseconds), and for Fast Ethernet, 5.12us. For Ethernet stations, collisions can be detected up to 51.2 microseconds after transmission begins, or in other words up to the 512th bit of the frame.
When a collision is detected by a station after it has sent the 512th bit of its frame, it is counted as a late collision
512th bit of frame is equivalent to 64 bytes of frame.
So I will say never trust the docs answers as they are many times misleading and many a times when you read dumps you will find this issue especially test kings. So just apply your logic and trust your answers and if you have any doubts you can discuss with your peers or post your doubts on this forum and someone will try to answer in best possible way.
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