On Sat, Sep 23, 2000 at 06:00:19PM +1100, Terry Collins wrote:
> [EMAIL PROTECTED] wrote:
> >
> > How about having the nodes in a cycle, where each one transmits, after
> > which the next one either transmits data or a "I'm here but no data
> > to transmit", so the next one could.
>
> It is called token ring.
Yes, but token ring involves specialised hardware. I's there a way of
adding on this functionality to standard twisted-pair/coax ethernets ?
A few ideas come to mind.
A user space solution involves waiting for a packet from the previous
machine before sending your data to the corresponding open socket.
This could be implemented in kernel space, eliminating some of the
user space latency.
There is, however, latency to send data to the card before the card
starts to transmit. If we are aiming for about 20% improvement, the
total latency round the whole set would have to be a good deal less
than this for the exercise to be worthwhile.
Ideally, the card could have its buffer loaded with data, and then
have the transmit delayed till a packet from the previous computer had
been received. The latency would be really low in this case. How
compatible is the common interface to ethernet cards with this approach ?
I'd imagine token rings implement this in hardware, seriously reducing
the latency. But I'm looking for a way to add the functionality to
current standard ethernet links.
--
John August
"Do you sell cats ?"
"Well ... yes and no"
- Schrodinger's Pet Shop
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