[Simh] Cluster communications errors

[Hunter Goatley]

On 7/19/2018 10:34 PM, Mark Pizzolato wrote:
> The improvement by setting the port speed to 10Mbit suggests
> that packet loss/overruns are happening and they are reduced
> by limiting the wire speed.

Agreed, though nothing ever indicated any errors or overruns: not the 
switch, not NCP or LANCP on any nodes.

> The arrival of DECnet's traffic might be causing a burst of traffic
> that still ends up overrunning another systems ability to receive
> it.  Do things change if you throttle the simh VAX down?
>
>        sim> SET CPU NOIDLE
>        sim> SET THROTTLE 25%

Wow. That was a flashback to 1987, when I was working on a VAX 11/730 
with four other developers at the same time. ;-) We all got lots of 
pleasure-reading done waiting for product builds....

Continued this morning: I ended up going to bed, it was taking so long. 
I woke this morning to find that the startup took about four hours to 
complete, and it had spent the next three hours losing and 
re-establishing communications every 40 seconds. I'm guessing the system 
was /so/ slow that it didn't respond fast enough to suit the other members.

So I took it down again and did SET THROTTLE 80%.  Still considerably 
slower, but workable. And as soon as DECnet started, it lost 
communication and re-established it. It's now two minutes farther into 
the boot with no further drops.

It drops between the "Starting DECnet" OPCOM message and the first 
"adjacency up" OPCOM message. After that, all is well.

Thanks.

Hunter


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