Late collision
From Wikipedia, the free encyclopedia
 |
This article may require cleanup to meet Wikipedia's quality standards. Please improve this article if you can. (January 2008) |
Late Collision is a type of collision found in the CSMA/CD protocol standard. If a collision error occurs after the first 512 bit times of data are transmitted by the transmitting station[1], a late collision is said to have occurred. Importantly, late collisions are not re-sent by the NIC unlike collisions occurring before the first 64 octets; it is left for the upper layers of the protocol stack to determine that there was loss of data.
Usually, possible causes are exceeded Ethernet cable length limits, incorrect cabling or a non-compliant number of hubs in the network. Bad network interface cards (NICs) can also cause late collisions, etc.
- ^ IEEE 802.3-2005 Part 1, IEEE section 5.2.2.1.10
[edit] Marbles through a pipe analogy
The pipe will represent the transmission medium, such as a copper cable. The marble will represent the data.
Imagine that you had a pipe that was big enough to push marbles through to and from each side. You could use this method to send and receive marbles with a friend a few meters away by thrusting marbles into our end of the pipe at a speed fast enough, that they would have enough momentum to make it through the pipe and out the other side of the pipe, within 1 to 2 seconds. If it takes longer than this, than you'd assume that a marble wasn't about to be sent, and you'd assume that you'd be able to send a marble down the pipe without the colliding.
If you extend the pipe without telling your friend, the time for the marble to get from one side to the other will take longer than expected. So a collision may occur, the marble would be damaged by the collision if it did get through, the marble might get lost in the pipe, or the marble might not even get to the other side.
