I
believe that the slot time is based on the propagation delay between the two
most distant stations and is tied to the time that a station needs to detect a
collision. In principle it is just a way of defining a relevant length of time.
The different stations use random integer multiples of this time to prevent
simultaneous retransmission of collided packets. It was the fact that this only
needs small random integers to generate relevant time delays using a simple
algorithm that I thought might be interesting. Hope it all works out
okay
Regards.
Doug.
-----Original Message-----> From: Doug Locke
From: Chuck Hackett [mailto:egroupscdh@WhiteTrout.net]
Sent: 09 March 2005 02:08
To: AVR-Chat@yahoogroups.com
Subject: RE: [AVR-Chat] Multimaster network
>
> If my memory serves, Ethernet uses the binary exponential backoff algorithm to
> avoid two stations recommencing transmitting after a packet collision. May be
> worth a look via Google.
I did look this up but it bases the back-off time on a "Slot Time" value and I
can't find a definition of this value. I suspect that it's based on the MAC
address or some other configuration value.
I was looking at a case where the two devices are identical (same software,
etc.) and share the data bus and reset signal - i.e.: they both have the same
historic view of the world so would thus generate identical values unless you
can use something like clock speed differences, etc. which we have discussed.
Cheers,
Chuck Hackett
"Good judgment comes from experience, experience comes from bad judgment"
7.5" gauge Union Pacific Northern (4-8-4) 844
http://www.whitetrout.net/Chuck