31 Mar
2021
31 Mar
'21
11:42 p.m.
On 2021-03-31 23:01, Paul Koning wrote:
[...]
Ah. Now I understand you. Basically, the actual VMS Multinet
implementation is the problem. Not running DECnet over TCP as such.
Then I fully agree with you. The VMS Multinet is just strange. And you
mentioned another thing that I have also observed. If the TCP link goes
down, it appears as if the VMS side actually don't get a circuit down,
and then things behave strange when the link comes up, with init packets
coming at strange points. This all leads to it taking longer than I
would expect should be required to reestablish the link when VMS
Multinet is involved.
That's why I said "Technically Multinet over TCP should work fine".
It should work fine, but in reality it don't because VMS Multinet is
doing strange things for no good reason (that I can figure out). Had
they just used what TCP provides, and signaled the information to
DECnet, it would have worked without a hitch.
Johnny
--
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
On Mar 29, 2021, at 2:25 AM, Johnny Billquist
<bqt at softjar.se> wrote:
On 2021-03-28 23:08, Paul Koning wrote:
I'm not sure what you think the problem is here. This would be interesting to
explore.
Restart notification, in my ears, seems to be about informing DECnet if the link had to
be restarted. Which, I would say, obviously can be done with Multinet over TCP, because
this is detected/handled by TCP just fine. And if the TCP connection is lost, all you need
to do is just inform DECnet that the link went down. And I do exactly that with TCP
connections.
If that were done by the other implementations things would indeed be ok. On Mar
28, 2021, at 4:40 PM, Johnny Billquist <bqt at softjar.se> wrote:
...
Technically, TCP should work just fine. But yes, Multinet even have some funny specific
behavior making even TCP a bit tricky.
No, technically Multinet TCP does NOT work
fine. The issue is that Multinet, whether over TCP or over UDP, fails several of the
requirements imposed on point to point datalinks by the DECnet routing spec. In
particular, it fails the requirement of "restart notification". In the TCP
case, it can be hacked to make it work most of the time, but architecturally speaking
it's flat out wrong.
The issue is that there is more to a point to point datalink that merely delivering a
packet stream from point A to point B. That's the main job, of course, but that by
itself is not sufficient in the DECnet architecture.