About 18 years ago I was talking on the phone with a customer while they were setting up a new system. We had to figure out the SCSSYSTEMID from the DECnet Phase IV address. Back then I could do that calculation in my head without looking up the details. The other day another customer was asking about the SCSSYSTEMID, and I had to look up the calculations, so I wrote this page to help me remember the next time the question is raised.
This will convert a SCSSYSTEMID into a DECnet Area, Node and MAC address. It will also convert the DECnet Area and Node into the SCSSYSTEMID and MAC address. And it can also convert a DECnet MAC address into the SCSSYSTEMID and DECnet Area and Node.
SCSSYSTEMID can be almost any integer from 1025 through 65535. SCSSYSTEMID cannot be a number that can be evenly divided by 1024 because numbers that can be evenly divided by 1024 will result in a Node number of 0. The DECnet Area is the number to the left of the decimal in the DECnet Address, it can be any integer from 1 through 63. The DECnet Node is the number to the right of the decimal in the DECnet Address, it can be any integer from 1 through 1023. When the DECnet Area and DECnet Node are combined into the DECnet Address the decimal point is simply a separator between the two numbers. The MAC address will start with AA-00-04-00- followed by two-byte words. They can be anything from 01 through FF.
If any of the fields have a red background, then the value you entered is invalid even if the field you are entering is not red. The details you entered will appear in the last row of the table below if the results are valid.
SCSSYSTEMID:
DECnet Address:
MAC: AA-00-04-00- -
Here are a few examples you can try.
| SCSSYSTEMID | Area | Node | DECnet Address | MAC |
|---|---|---|---|---|
| 1025 | 1 | 1 | 1.1 | AA-00-04-00-01-04 |
| 53269 | 52 | 21 | 52.21 | AA-00-04-00-15-D0 |
| 53270 | 52 | 22 | 52.22 | AA-00-04-00-16-D0 |
| 65535 | 63 | 1023 | 63.1023 | AA-00-04-00-FF-FF |