This article is from the Ethernet FAQ, by James Messer James@NetworkUptime.com with numerous contributions by others.
A collision is considered late if the jam occurs after 512
bit-times, or 64 bytes. Collisions that occur after the first 64
bytes of a frame may be indicative of a network design problem (the
network is so large the jam cannot traverse the entire length in 32
bit-times), or a hardware or Ethernet firmware issue.
When collisions do not propagate the network quickly enough, a
collision could occur between two stations without the stations
aware that the packets collided. In this situation, the frames are
simply lost, and the upper-layer protocols must begin a
retransmission process to retransmit the information. These
retransmissions can cause large delays, especially at the