Date   : Fri, 29 Jul 2005 17:14:38 +0200 (BST)
From   : Johan Heuseveldt <johan@...>
Subject: Re: Econet-Ethernet bridge

Hi Jules,

On Fri 29 Jul, Jules Richardson wrote:
> On Fri, 2005-07-29 at 13:22 +0200, Johan Heuseveldt wrote:

[snip]

> > It doesn't seem logical to me that only one of the four sockets could
> > be upgrade from 2K to 8K. Having only 8K puts restrictions on the
> > packet size. I think Mike got it right; see later.
> > But a good schematic would give the answer.
> 
> Does it actually have to do much though? I mean isn't functionality just
> a case of watching packets on each network interface and if they're not
> destined for that interface, write them out to the other interface?  I'm
> surprised much memory's needed to do that.

The nets can have different speeds setup for their clocks.

  1 From hi to lo speed you need you need some queue, possibly
     still sending;
  2 From lo to hi speed you need the store the data completely, and 
     after being complete, it can be send

 1 is a bit complicated in comparison with 2, and
 2 can't use the technique of 1

 perhaps both use the technique or 2, so only one protocol is needed.
 It does puts both nets on hold for longer periods between the frames
 in the 4-way handshake, than without bridge.

TBH, I don't how how it is really happening, but because of different
speeds between the nets, it isn't as simple as you thought! :-)
Time to invetigate the ROM code.

> I know next to nothing about the high level Econet protocols, but I'm
> surprised the bridge needs to maintain any kind of state (and therefore
> need much memory)

Caching/queueing, and I would call this low level?
(should be transparent for any application)

> Presumably larger packet sizes really hit performance on the network, so
> they were typically pretty small.

Even without bridge, that would make sense, to maintain a good
responsiveness for the other machines on the net for their user's sake. :-)


greetings,
Johan

-- 
Johan Heuseveldt <johan@...              >
  aka  waarland

  The best place is a Riscy place
 
I'm always late. My ancestors arrived on the June Flower.