DDCMP protocol on serial ports

[Phelipot]

DDCMP protocol on serial ports
Using OpenVMS 7-3-2 and needing DDCMP protocol on RS232 lines to link OpenVMS AlphaServer with an old equipment.

But the HP answer (11-JUL-2000) is :
Asynchronous DDCMP is not available on OpenVMS Alpha.
cf http://h71000.www7.hp.com/wizard/wiz_4651.html

We would find for example :
- an Asynchronous DDCMP Protocol Software usable on OpenVMS AlphaServer (ready to use)
- AND/OR the source software (Asynchronous DDCMP Protocol Software) developed on an other Operating System.

Thanks for any idea that could help us.

[Ian Miller.]

as far as I know DDCMP was never implemented for OpenVMS Alpha. Have you looked at the older DECrouter products or talked to dnpg
http://www.dnpg.com who inherited the DEC networking products?

[Antoniov.]

Hi Phelipot,
I used DDCMP protocol in past ove vax. DDCMP protocol is not supported on alpha CPU; I don't know why.
I suppose you can use PPP or SLIP protocol and DecNet over TCP/IP but I never used this solution. When I migrated form VAX to alpha I used kermit to transfer files using serial port.
PPP is now part of operating system (you can type HELP PPP) as TCP/IP suite. For Decnet over TCP/IP you need license.

Antonio Vigliotti

[Bojan Nemec]

Hi Phelipot,

As you already know, no DDCMP on alpha. When I read your post, I remember that Linux guys are porting DECnet on Linux (I try it and for the short time I tested works fine), but looking to their FAQ about DDCMP, they says - no DDCMP but that some work is going on (slowly). On their home page you can found some documentation about DDCMP V4.1 protocol. You can ask them how far are they. Here is a link for the DECnet for Linux
http://linux-decnet.sourceforge.net/

On that page I found a link to Other software that is Linux and OpenVMS or VAX related. There is a DDCMP to ethernet convertor for CHARON-VAX. It is abbout 20K of code to which you can look. There is the link http://linux-decnet.sourceforge.net/links.html


Googling, (just DDCMP in the query) I found an old post (1988) in a mailing list where somebody says that he wrote a DDCMP interface in C. Here is the link http://www-mice.cs.ucl.ac.uk/multimedia/misc/tcp_ip/8801.mm.www/0295.html

If you can write a program on this old equipment, I will option to a private protocol. See yours previous thread how to implement such a protocol.

Bojan

[Bojan Nemec]

Hi,

Another idea. You can use an VAX (or maybe CHARON-VAX) with an ethernet card and serial lines and routing decnet as a router betwen Alphas and old equipment.

Bojan

[Antoniov.]

Hi Bojan,
might be simpler install and use PPP protocol that works within serial line and can be used even by tcp/ip suite.
DDCMP is legacy protocolo of Dec to connect serial port in decnet IV; because HP hints use Decnet plus instead Decnet IV and tcp/ip in included in vms installation I guess between two alpha it's better (also for future features) use PPP.
This is my own idea, obviously.

Antonio Vigliotti

[Bojan Nemec]

Antonio,

I know that this will be better, but i think that Phelipots problem is some old industrial equipment which uses DDCMP. It can be an old PDP runing RSX, an old VAX with VAXeln or something else (DDCMP and all DECnet protocols are open, so enyone can implement them).

Bojan

[Phelipot]

Hi,

Bojan is right, our concern is not to use DDCMP to carry DECNET or TCP on serial links.

DDCMP was used in the early 90's to exchange data between VAXs of different industrial system provider as "standard" protocol on serial links.

Today, we are migrating one of the industrial system on AlphaVMS.

To help us we have the listing of the VaxELN DDCMP driver in Pascal, but migration and tests on OpenVMS remain to do.

Phelipot

[Bojan Nemec]

Hi,

Probably you dont need the full functionality of DECnet. Which application layer do you need?
With application layer I mean file copy, directory, task to task or something else. Maybe it will be easier implement only a specific layer rather than the whole protocol.

Bojan

[Phelipot]

Bojan,

Our need is on the DDCMP driver, a link protocol driver, able to carry task to task communication and providing : frame and check-sum generation/control, RS232 interface handling, master/master handshaking...

Phelipot

[Ian Miller.]

I think it is looking like you will have to write your own. You may be able to use something from the references already given. The DDCMP spec can be obtained from here
http://ftp.digital.com/pub/DEC/DECnet/PhaseIV/ddcmp.txt

[Bojan Nemec]

Phelipot,

I see, a hard task. How many DDCMP nodes are there?
I look at the ethddcmp. This is practicaly a serial line to ethernet converter. Probably it was writen, because the demo version of the charon-vax does not support any ethernet controlers. With some small modifications probably you can get a converter from serial to ethernet. The modifications which I saw are: Read/Write to serial line (now it works with a socket, because charon-vax creates a socket for each terminal), some CRC testing when reading from serial line. You can build a small linux machine (I think that the whole operating system and programs will be arround 1M) which you can use to attach your DDCMP industrial system to the network.
Writing this I figure out that this solution is very similar to the VAX as a router. The VAX is better because you can have more than one DDCMP line connected to the it.

Bojan

[Antoniov.]

Phelipot,
you could try translating vax images of ddcmp into alpha images with vest.
I'm dubt this can work but you can try in few minutes.

Antonio Vigliotti

[Phelipot]

Thanks to all for replies,

I cannot use any front-end Vax or Linux machine, or converted code, for the following reasons :

-the system is already a front-end with other protocols and Decnet

-the application is involved in the security of people, so all software must be tested, validated and sources must be fully maintainable (on 1990, when application was built, any other OS than VMS was rejected for security, stability and robustness reasons. At the moment, the system never stops without operator manual command since delivery on 1993.)

If an unofficial version of DDCMP on AlphaVMS has existed, the use would have been submitted to : have a copy of the source (with the rights to get it) and carefully validate it.