Late collision

Late Collision in computer networking is a type of collision found in CSMA/CD based protocols. Specifically a late collision is one that happens further into the packet than is allowed for by the protocol standard in question.

In 10 megabit shared medium ethernet, if a collision error occurs after the first 512 bits 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.

As a correctly set up CSMA/CD network link should not have late collisions, the usual possible causes are full-duplex/half-duplex mismatch, exceeded Ethernet cable length limits, or defective hardware such as incorrect cabling, non-compliant number of hubs in the network, or a bad NIC.

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