On Saturday, March 11, 2017 at 1:16 PM, Johnny Billquist wrote: > On 2017-03-11 19:41, Mark Pizzolato wrote: > > On Saturday, March 11, 2017 at 10:06 AM, Johnny Billquist wrote: > >> On 2017-03-11 17:18, Mark Pizzolato wrote: > >>> 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. > >> > >> I don't know for sure, but I assume that Tim just meant that he will > >> let LAVC do as LAVC does, without him doing anything. > >> And LAVC itself might be using ethernet multicasting. > >> This is no more an issue than DECnet communication, which also > >> requires access to the raw ethernet. > > > > True. It could use the existing raw Ethernet access methods, but that > > approach would have the following issues: > > 1) Some platforms require significant privilege (root) to do this. > > Same as DECnet. > > > 2) He would have to re-invent much of what LAVC does. > > I thought he was talking just about LAVC, not inventing something new. > > > 3) The same problems that exist today on *nix hosts to provide a > > mechanism for multiple simulators running on the same host to be able > > to concurrently communicate with each other will exist. > > > > An IP multicast based solution lets the host OS solve much of this. > > Either you or me is missing something. I thought he was just talking about > using LAVC (and thus raw ethernet) for clustering. Meaning he'll just fire up > is > simh instance, and start running. And that's the end of it. > > Seems like you are thinking he is going to implement something. Not sure > exactly what. Emulate CI?
That is where he started this discussion, and from what he had said above, it seemed like that was still the plan. > Possible, but will require a lot more work than just > transporting the bytes over the network. But, that said, it probably makes > sense to use IP instead of raw ethernet if you are going to implement this. > And > my reasoning for that don't have as much to do with any network access > (which you still will want to have for DECnet anyhow), but because CI frames > are something like 8K in size. So you're going to have to implement some kind > of complex layer on top of ethernet if you do that. And then you are going to > get close to what IP/UDP will do for you anyhow, so why reinvent the wheel? Exactly! I think I vaguely remember something from my discussion with Matt about their being some sort of virtual circuit functionality in the set of capabilities the CI/SCS functionality provides, so leveraging UDP multi-cast along with TCP would be natural solutions to both of those problems. - Mark _______________________________________________ Simh mailing list [email protected] http://mailman.trailing-edge.com/mailman/listinfo/simh
