[HECnet] Old protocols in new ones

[Johnny Billquist]

On 2021-03-31 23:01, Paul Koning wrote:
> 
> 
>> On Mar 29, 2021, at 2:25 AM, Johnny Billquist <bqt at softjar.se> wrote:
>>
>> On 2021-03-28 23:08, Paul Koning wrote:
>>>> 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.
>>
>> 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.

[...]

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