Re: [ECOS] Problem with RX packets

[Andrew Lunn <andrew at lunn dot ch>]

> Ethernet standard (at least 100 mbit over copper cable) extends all
> packets to 64 Byte minimum (don't ask me why, I forgot that).

It comes from the old 10Mbit/s standard which truly was CSMA/CD.  For
the CD, ie Collision Detection, part to work, it was required that the
packet was long enough that the first bit could get from one end of
the cable to the other, be corrupted by a new transmitter, that
transmitter would detect it had just collided, and change from sending
its packet to sending a collision signal. This collision signal then
needs to traverse the full length of the cable to the first sender,
who while still sending its packet will receive the collision signal,
know its all gone wrong, back off and try again later. 64 bytes is the
required minimum packet length for the maximum length of allowed
cable.

With modern ethernet with twisted pair and switches, this is no longer
needed. Collisions should never occur, since its a point to point link
to the switch. The only difficult is when running in half duplex mode.

         Andrew

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