Ethernet: Late Collision
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## Ethernet: Late Collision

When two systems' transmissions happen at the same time, the resulting contention is called a collision. Collisions are a normal part of Ethernet communications and do not imply any error condition. A “late collision” is similar to an ordinary Ethernet collision, except that it occurs after all hosts (workstations on the network) should have been able to notice that a host was already transmitting. It is normal for collisions to occur during a “collision window”, but once that period of time passes, only one system should be transmitting, and all other systems should defer to it.

A late collision indicates that another system attempted to transmit after your machine (the one displaying the message) has transmitted at least the first 60 bytes of its frame (packet) Since the amount of time it takes to send 60 bytes (50.2 microseconds) is long enough for round trip propagation delay on even the largest network, a correctly configured network will never allow this transmission condition. Something related to the network topology is causing a problem.

A late collision invariably indicates that one or more packets were lost by the Ethernet. They will almost always be retransmitted by the “higher network layers,” but only after a delay.

Late collision messages are sent both to the console and to /usr/adm/SYSLOG. If you are seeing these messages the more common causes are exceeded Ethernet cable length limits, partially connected or loose cables, or hardware failure.

To isolate the problem first look for violations of the Ethernet cable limits. For 10BASE5 cable (thicknet) the maximum segment length is 500m; for 10BASE2 cable (thinnet) the maximum segment length is 200m. The length of a transceiver cable, the cable that goes between a machine's Ethernet port and its transceiver, should not exceed 50m. If these distances are exceeded, this can lead to late collision messages. Next, make sure the connectors are all secure. If the sliding latch on the AUI connectors has come loose, you may see late collision messages.

For more information on this error, see man `ethernet`. For general networking information see the IRIX Admin: Networking and Mail.

If the problem persists, contact your Network Administrator.

For information on how to configure or disable System Alerts, click here.

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