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From: STJOHNS@SRI-NIC.ARPA
Newsgroups: comp.protocols.tcp-ip
Subject: Re: DDN Standard X.25 address questions
Message-ID: <[SRI-NIC.ARPA]Tue,.6.Oct.87.06:25:25.PDT.STJOHNS>
Date: Tue, 6-Oct-87 09:25:00 EDT
Article-I.D.: <[SRI-NIC.ARPA]Tue,.6.Oct.87.06:25:25.PDT.STJOHNS>
Posted: Tue Oct  6 09:25:00 1987
Date-Received: Fri, 9-Oct-87 06:21:29 EDT
References: <12340231308.11.SATZ@MATHOM.CISCO.COM>
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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