Re: DDN Standard X.25 address questions


STJOHNS@SRI-NIC.ARPA
6 Oct 1987 06:25-PDT


The 1983 version of the DDN X.25 standard is the most recent.

1)No DNIC has been assigned to any component of the DDN, and at
this writing, it doesn't look like one will be assigned. There
are only some 20 DNICs allocated to the US.

2) Using the current mappings, the physical mappings are directly
translatable into a PSN/Host Port pair. Logical addressing is
implemented, but currently not used by anyone since for it to
work properly for the IP world, everyone on the subnet has to
implement a form of the Logical addressing. Logical Addressing
allows several forms of address indirection: a) single host with
multiple ports, b) multiple hosts on different ports providing
the same service (eg Gateways), c) multiple hosts on the same
port, time sharing the port. In each case, the address is
resolved at call setup time into a physical address.

3) On the C/30 network, using X.25 standard with IP above it,
sub-addresses should NOT be specified and should be ignored if
they are.

As for the what and why, keep in mind, we have to maintain a
valid mappiung from IP to whatever X.25 address we pick. That
has a lot to do with "why".

Mike



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