Re: DDN X.25 mapping

Mark Crispin (MRC@PANDA.COM)
Mon, 14 Sep 87 13:13:31 PDT

For the record, both BBN and PANDA TOPS-20 assume that any Class C
PSN-based network will have the host number in the high order 2 bits,
and the PSN in the low order 6 bits of the fourth octet. This is the
format which we used in the good old days of NCP and 32-bit leaders,
for those of us old enough to remember that far back (am I betraying
my age????).

DEC TOPS-20 doesn't handle non-class A PSN's at all, nor does any
version of TOPS-20 I know of handle X.25 interfaces (the DEC IMPterface
is an 1822 device). I think that DEC is adopting the PANDA algorithm

I know of no controversy about the format a Class B PSN network address,
or, at least TOPS-20 and Unix agree on having the host number in the
third octet and the PSN number in the fourth octet.

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