Re: dealing with collisions, dropped packets

[sthaug () nethelp no]

> > A collision on half duplex media (such as a hub) is a *normal* and
> > *expected* occurence, and does *not* cause a packet to be dropped.
>
> > Note that this does not apply to "late collisions" which are quite
> > different - late collisions are signs of *error* (for instance a
> > duplex mismatch).
>
> Sorry I did not make myself clear.  I know very well that collisions on hubs 
> are normal.  What I wasn't sure of was if tcpdump was seeing the first 
> transmission of a packet, and then dropping the second copy of the packet 
> when it is recent by the originating host so as not to skew statistics or 
> something.

Um, I'm still not sure if you understand. A normal collision is detected
during the first 512 bits of the packet. There is no retransmission of
the whole packet in case of collision (and thus no second copy of the
packet). One packet is sent, one packet is received.

Steinar Haug, Nethelp consulting, sthaug () nethelp no
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