Late Collision on Transmit errors

Late-collision errors that occur when a card has transmitted enough of a frame that the rest of the network should be aware that the network is currently in use, yet another system on the network still started to transfer a frame onto the line. They're the same as regular collision errors, but were just detected too late.

Depending on the protocol, these types of errors can be detrimental to the protocol's overall throughput. For example, a 1% packet loss on the NFS protocol using the default retransmission timers is enough to slow the speed down by approximately 90%. If you experience low throughput with your networking, check to make sure that you aren't getting these types of errors. Typically, Ethernet adapters don't retransmit frames that have been lost to a late collision.

These errors are a sign that the time to propagate the signal across the network is longer than the time it takes for a network card to place an entire packet on the network. Thus, the offending system doesn't know that the network is currently in use, and it proceeds to place a new frame on the network.

The nodes that are trying to use the network at the same time detect the error after the first slot time of 64 bytes. This means that the NIC detects late collisions only when transmitting frames that are longer than 64 bytes. The problem with this is that, with frames smaller than 64 bytes, the NIC can't detect the error. Generally, if you experience late collisions with large frames on your network, you're very likely also experiencing late collisions with small frames.

These types of errors are generally caused by Ethernet cables that are longer than that allowed by the IEEE 802.3 specification, or are the maximum size permitted by the particular type of cable, or by an excessive amount of repeaters on the network between the two nodes.

Another thing to note is that these errors may actually be caused by a node on the network that has faulty hardware and is sending damaged frames that look like collision fragments. These damaged frames can sometimes appear to a network card to be a late collision.