[HECnet] Hecnet and DDCMP

Excellent. Then it do not require anything more than a link that can transport a stream of bytes. You made it sound (to me), as if DDCMP expected the underlying link to provide more structure, which is what I wanted to check. Johnny On 2012-01-05 02.23, Paul_Koning at Dell.com wrote: Yes, DDCMP does its own block delimiting on both sync and async lines, basically the same way for both. It recognizes the header by byte patterns plus good CRC, and the payload framing is controlled by the payload byte count that's mentioned in the header. It's all in the spec. Take a look, it's a very clear and very simple document. paul -----Original Message----- From: owner-hecnet at Update.UU.SE [mailto:owner-hecnet at Update.UU.SE] On Behalf Of Johnny Billquist Sent: Wednesday, January 04, 2012 6:46 PM To: hecnet at Update.UU.SE Subject: Re: [HECnet] Hecnet and DDCMP On 2012-01-04 23.15, Paul_Koning at Dell.com wrote: I assume there has to be a bit more to it, because DDCMP is a packet based protocol (not a stream protocol as TCP is) and the higher layers rely on that. So there presumably is some form of framing in the emulated data stream to indicate where the packet boundaries are. Paul, how does this work when you have DDCMP over an asynch serial line? There are no frames there. It is just a stream of bytes at the physical layer, exactly the same as TCP for example. Yet, DDCMP talks over that too... DDCMP must be implementing the blocking/deblocking on its own in that case. Johnny paul -----Original Message----- From: owner-hecnet at Update.UU.SE [mailto:owner-hecnet at Update.UU.SE] On Behalf Of Rob Jarratt Sent: Wednesday, January 04, 2012 5:11 PM To: hecnet at Update.UU.SE Subject: RE: [HECnet] Hecnet and DDCMP All I do in SIMH is to take the data bytes each end wants to send to the other end and send them over a socket, so I don't get involved with DDCMP itself. Both ends have to be SIMH for this to work. I don't do anything at the actual hardware level, although that would be nice. I think you can get synchronous serial cards for the PC but they are quite expensive. Regards Rob -----Original Message----- From: owner-hecnet at Update.UU.SE [mailto:owner-hecnet at Update.UU.SE] On Behalf Of Paul_Koning at Dell.com Sent: 03 January 2012 21:18 To: hecnet at Update.UU.SE Subject: RE: [HECnet] Hecnet and DDCMP DMC-11 speaks DDCMP V3.1 (give or take some bugs in the "high speed" version). But that's sync only. Depending on what you want to talk to, a DMC (or its relatives DMR-11, DMP-11, or DMV-11) may not help; if the other end speaks DDCMP over an async link (UART) then it won't work because the character framing doesn't match. That said, I wonder what it means to emulate a DMC-11. You could have it speak DDCMP over a UART, or something else entirely. If the former it would talk to another DDCMP node; if the latter it would not but it would still work for tying one emulated DMC-11 to another. If you want DDCMP, one approach is to get a copy of the spec, and implement what it says. That works; it is how I implemented DDCMP support for RSTS V10 (based on an earlier version based on V9.6). The protocol is quite simple and the spec is well enough written that, if you do what it says, the result WILL interoperate with hardware such as the DMR-11. The only tricky one is the DMC-11 because it has some undocumented bugs; the main one I remember is that the high speed version can't handle back to back packets. I wish I could contribute the code I wrote but I can't, for various reasons one of them is that it's a RSTS device driver and written in 100% assembly language. It would not be hard to do a version for other platforms; I once looked at a Linux terminal protocol handler (forgot what that is called) that could hook into DECnet/Linux. Didn't get far enough on that, though. paul -----Original Message----- From: owner-hecnet at Update.UU.SE [mailto:owner-hecnet at Update.UU.SE] On Behalf Of Mark Abene Sent: Sunday, January 01, 2012 6:06 PM To: hecnet at update.uu.se Subject: Re: [HECnet] Hecnet and DDCMP Jarratt, did you make this publicly available on the SIMH list? It would be great to have a DMC11 device emulated, since I insist on running RSTS/E v8 (for historical reasons... it was the last real RSTS before "the pollution"). RSTS/E v8 doesn't have ethernet support, so the only way I could have DECnet is via a (previously unemulated) DMC11 interface. Does yours work well? -Mark On Sun, Jan 1, 2012 at 3:23 AM, Jarratt RMA <robert.jarratt at ntlworld.com> wrote: Working with a friend, I have written a SIMH emulation of the DMC11 device, so you can do this with SIMH. It tunnels the bytes sent to/from the device over a socket. We have used the SIMH emulation to connect my friend to HECnet over a (simulated) DMC11. The bit I am not entirely sure about is to what extent this is using DDCMP as I don't have a full understanding of DDCMP. Regards Rob On 31 December 2011 18:46, The Presence<tpresence at hotmail.com> wrote: Hey guys, Has anyone worked out a mechanism to connect a node to hecnet using DDCMP? Perhaps some tunneling technology over IP, or virtualized serial? Kevin