[HECnet] Same MAC address on different nodes

[Johnny Billquist]

On 2014-05-25 19:04, Hans Vlems wrote:
You are absolutely correct, however what you see happening is strange.

The fact that performance sometimes sucks? It is not that strange. As I have mentioned a few times, DECnet do *not* handle lots of lost packets very well. It will degrade to horrendous performance.
This is easy to observe, if you have the right equipment around.

OK, I got the OS wrong. Because VMS and RT-11    are all I need :-)

:-)

That said, it should work. I'm not sure how RSX handled area routing but    30 years ago we were warned to configure endnodes because ALL the overhead incurred by circuit routers...

Huh? With ethernet, communication with adjacent nodes works without involving any routers anyway. And if you need to talk with anything beyond, you're going to go through the router on the way there anyway.
Really, unless you actually have several interfaces, there is no gain in running a router compared to an endnode. However, running a router definitely use up more resources, which is a disadvantage.

Anyway, i'd stop using the same 08-00-2B address on two nodes, shutdown the simulators the VM host and the real iron.

Would still not make any difference, which I have pointed out several times now, and also what Jean-Yves have been observing the last two days.

Really. There is no black magic here. I can explain every bit of it if someone needs more convincing.

Essentially, the MAC address in the actual ethernet controller (or the MAC address set before boot in simh) is irrelevant. Once DECnet starts running, that MAC address is not used anymore. It is just a trivia piece of information so that you can know what the hardware MAC address from the factory is. It is not used by anything, especially not anything related to network communication.

The VM host in turn cares even less, since whatever MAC address simh plays around with is fully local to simh, and does not affect the VM host.

Any questions?

	Johnny


Verzonden vanaf mijn BlackBerry 10-smartphone.
    Origineel bericht
Van: Jean-Yves Bernier
Verzonden: zondag 25 mei 2014 18:47
Aan: hecnet at Update.UU.SE
Beantwoorden: hecnet at Update.UU.SE
Onderwerp: Re: [HECnet] Same MAC address on different nodes

At 6:27 PM +0200 25/5/14, Hans Vlems wrote:

My apologies, it's been too long to remember rsx. A netgen is too
much work for an experiment.

No need to apologize :)


Background for the request: I had problems running two area routers
on the same lan, though just one was simh based. Both were VMS
though.

By running complex software under emulation, we take risks that
things don't work as expected. By adding a layer more with
virtualization, I take still more risks. What is amazing is that it
works most of the time.





-- 
Johnny Billquist                                   || "I'm on a bus
                                                                  ||   on a psychedelic trip
email: bqt at softjar.se                         ||   Reading murder books
pdp is alive!                                         ||   tryin' to stay hip" - B. Idol