[Simh] LAVC

[Johnny Billquist]

On 2017-03-11 22:33, Tim Stark wrote:
> Yeah.
>
> I believe so.  That is possible to replace CI/DSSI physical layer with UDP over IP multicast to embed SCS/MSCP packets to other hosts and HSCs at once.

Of course this is doable. The network part itself is not even hard. The 
big work is actually implementing the CI controller emulation. Once you 
have the packet to send out, you just send it.

> That's why Charon-VAX already emulates virtual CI and HSJ for VAX 66x0 emulation. I read Charon documents and learned that emulated CI uses SCS/MSCP over IP method.

Which should be a pretty obvious solution.

> That is same way like BITNET over TCP/IP and DECnet over TCP/IP (HECnet provides bridge adapter software).

One should remember that my bridge is nothing comparable to this. All it 
does is bridge two ethernet segments together, so that they appear to be 
one. It's plain ethernet on both sides, so it's a really stupid simple 
thing. Packets on one segment gets injected into the other segment. 
Since it's ethernet on both sides, nothing more needs to be done.

Doing CI on ethernet would be a much more complicated challenge. CI over 
IP will be easier, since the capabilities of IP are better at handling 
the requirements that CI will demand.
But you still need to emulate the rest of the CI hardware, which 
contains both the host interface parts, and also possibly some 
addressing and filtering, and the actual transportation of the bits.

> That’s why I studied Computer Networking and learned lot about ISO layers at university.
> Also about bridging and routing methods.

I hope you also learned that the ISO layers are a good theory, but is 
not applicable to TCP/IP, which is not designed according to the ISO layers.

	Johnny

>
>
> Tim
>
> -----Original Message-----
> From: Mark Pizzolato [mailto:Mark at infocomm.com]
> Sent: Saturday, March 11, 2017 11:19 AM
> To: Tim Stark <fsword7 at verizon.net>; simh at trailing-edge.com
> Subject: RE: [Simh] LAVC
>
> On Saturday, March 11, 2017 at 5:49 AM, Tim Stark wrote:
>> Thanks for many replies. I learned a lot about VAX clustering. I will
>> use multicast Ethernet for clustering.  I have more one question. Is
>> that possible to emulate HSC controllers with LAVC access?
>
> When Matt Burke and I were discussing the CI concept, we picked IP Multicast as transport for the very specific reason that all modern host systems will have natural user mode programming access to implement this functionality.  Attempting to create your own Ethernet multicast protocol (non-IP based) will have portability complexities on different platforms due to the fact different platforms have varying support (and potentially require privilege) to present and/or receive raw Ethernet frames to/from a LAN.
>
> - Mark
>
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-- 
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