[HECnet] SIMH experience?

[Johnny Billquist]

On 2020-02-25 02:17, Paul Koning wrote:
> 
> 
>> On Feb 24, 2020, at 8:01 PM, G. <gerry77 at mail.com> wrote:
>>
>> Probably I'm missing something else, but wouldn't the TCP flavor be of
>> comparable reliabilty to other solutions, given that TCP would present to
>> the point-to-point link a dependable error-free path?
> 
> It would be possible to build something similar to the Multinet protocol, over TCP, that is architecturally correct.  But what Multinet actually does isn't, so no, it does NOT provide reliability comparable to other solutions.
> 
> Take a look at the DECnet routing layer spec, the list of requirements it gives for "point to point data links".  That's what Multinet pretends to be, but it fails to implement many of the stated requirements.
> 
> For the TCP case, a correct design would tell the routing layer about the establishment of a new connection and the loss of that connection.  Multinet does not do this.  So the synchronization services that Routing expect the data link to provide are missing.

I'm signalling to the DECnet layer when a TCP connection is established 
or lost. So it's not impossible to do this.
However, Multinet is doing weird things, which I think are carryovers 
from their UDP implementation. Which means I have to do some really 
strange stuff in order to properly interoperate with VMS Multinet from 
RSX. As an alternative, I can run TCP links in the more straightforward 
form as well, which is way simpler and makes more sense.
But that obviously only works against other RSX systems. Might be that 
it could also work towards PyDECnet, or else this would at least be easy 
to implement.

   Johnny

-- 
Johnny Billquist                  || "I'm on a bus
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