On Mon, 2 Feb 1998, Hans-Christian Becker wrote:
> Could anyone please explain what a "late collision" is?
> I'm running 1.3, GENERIC-55 & GENERIC-56.

A late collision is when a collision is detected after the time when
collisions are supposed to occur (within the first 512 bits or
something?) From what I've read, this generally means your network's
collision domain is larger than it's supposed to be (i.e. length limit,
number of repeaters, or something like that has been exceeded). So, if
you really are getting late collisions, it's a network problem.

Ah, here's something from the comp.dcom.lans.ethernet FAQ
(http://www.faqs.org/faqs/LANs/ethernet-faq/):

05.13Q: What is a late collision?
     A: A late collision occurs when two devices transmit at the same time,
        but due to cabling errors (most commonly, excessive network segment
        length or repeaters between  devices) neither detects  a collision.
        The reason this happens is because the time to propagate the signal
        from one end of the network to another is  longer than the time  to
        put the entire packet on the network, so the two devices that cause
        the late collision  never see that  the other's sending until after
        it  puts the  entire  packet on  the network.  Late  collisions are
        detected by the transmitter after the first  "slot time" of 64 byte
        times.  They  are only  detected  during  transmissions of  packets
        longer than 64 bytes.  It's detection is exactly  the same as for a
        normal collision; it just happens "too late."

        Typical causes  of late  collisions are  segment cable  lengths  in
        excess  of  the  maximum  permitted  for  the  cable  type,  faulty
        connectors  or  improper cabling,  excessive  numbers of  repeaters
        between  network devices,  and defective Ethernet  transceivers  or
        controllers.

        Another  bad thing about  late  collisions  is  that they occur for
        small packets also,  but cannot be detected by the transmitter.   A
        network  suffering a  measurable rate of late collisions (on  large
        packets)  is  also  suffering  lost   small  packets.   The  higher
        protocols do  not cope well with such losses.  Well, they cope, but
        at much  reduced speed.  A 1% packet  loss is enough  to reduce the
        speed of NFS by 90% with the default retransmission timers.  That's
        a 10X amplification of the problem.

        Finally, Ethernet  controllers  do not retransmit packets  lost  to
        late collisions.
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