[Simh] Cluster communications errors

[Mark Pizzolato]

On Wednesday, July 18, 2018 at 2:32 PM, Paul Koning wrote:
> > On Jul 18, 2018, at 5:27 PM, Mark Pizzolato <Mark at infocomm.com> wrote:
> >
> > On Wednesday, July 18, 2018 at 2:19 PM, Paul Koning wrote:
> >>> On Jul 18, 2018, at 5:03 PM, Hunter Goatley <goathunter at goatley.com>
> wrote:
> >>>
> >>> On 7/18/2018 3:38 PM, Hunter Goatley wrote:
> >>>> I know it's currently as set to autosense. I'll try forcing the
> >>>> speed and duplex.
> >>>>
> >>>
> >>> I was told:
> >>> The router is reporting that the port auto-sensed 1Gbit duplex, but
> >>> I just manually forced it to that to be sure.
> >
> > It might be better to hard set the Linux simh host system's port to
> > 10Mbit on the switch.  That would help with the potential for
> > overrunning the original DEC hardware...
> 
> DEC hardware tends to handle line rate traffic; a lot of other Ethernet
> hardware does not, especially not earlier models.  I remember arguing with the
> DECnet/DOS folks that no, we would not modify the DECnet architecture to
> handle the single buffer "design" of the 3c501.
>
> But if you have speed mismatches, you're likely to have congestion loss, unless
> the bursts are less than the switch buffer quota.  Some switches have
> thousands of buffers; other (inexpensive) ones have only a surprisingly small
> number and can easily give you congestion loss.

Well, not all systems and hardware can actually handle back to back 
packets even at 10Mbits.   The XQ THROTTLING is based on the throttling that
Johnny Billquist implemented in his bridge which was needed to allow his
physical systems to be able to communicated with simulated systems without
crazy packet loss...

- Mark