MILNET Parameters

MILNET LINK NUMBERS


The word "link" here refers to a field in the original MILNET Host/IMP
interface leader.  The link was originally defined as an 8-bit field.
Later specifications defined this field as the "message-id" with a
length of 12 bits.  The name link now refers to the high order 8 bits of
this 12-bit message-id field.  The Host/IMP interface is defined in BBN
Report 1822 [BBN1822].

The low-order 4 bits of the message-id field are called the sub-link.
Unless explicitly specified otherwise for a particular protocol, there
is no sender to receiver significance to the sub-link.  The sender may
use the sub-link in any way he chooses (it is returned in the RFNM by
the destination IMP), the receiver should ignore the sub-link.


Link Assignments:

Decimal   Description                                   References
-------   -----------                                   ----------
0-63      BBNCC Monitoring                                    [MB]  
64-149    Unassigned                                         [JBP]
150       Xerox NS IDP                            [ETHERNET,XEROX]
151       Unassigned                                         [JBP]
152       PARC Universal Protocol                      [PUP,XEROX]
153       TIP Status Reporting                               [JGH]
154       TIP Accounting                                     [JGH]
155       Internet Protocol [regular]                 [RFC791,JBP]
156-158   Internet Protocol [experimental]            [RFC791,JBP]
159       Figleaf Link                                      [JBW1]
160       Blacker Local Network Protocol                    [DM28]
161-194   Unassigned                                         [JBP]
195       ISO-IP                                      [RFC926,RXM]
196-247   Experimental Protocols                             [JBP]
248-255   Network Maintenance                                [JGH]



MILNET LOGICAL ADDRESSES

The MILNET facility for "logical addressing" is described in [RFC878]
and [RFC1005].  A portion of the possible logical addresses are
reserved for standard uses.

There are 49,152 possible logical host addresses.  Of these, 256 are
reserved for assignment to well-known functions.  Assignments for
well-known functions are made by the IANA.  Assignments for other
logical host addresses are made by the NIC.


Logical Address Assignments:

Decimal    Description                                  References
-------    -----------                                  ----------
0          Reserved                                          [JBP]
1          The BBN Core Gateways                              [MB]
2-254      Unassigned                                        [JBP]
255        Reserved                                          [JBP]



MILNET X.25 ADDRESS MAPPINGS


All MILNET hosts are assigned addresses by the Defense Data Network
(DDN).  The address of a MILNET host may be obtained from the Network
Information Center (NIC), represented as an ASCII text string in what
is called "host table format".  This section describes the process by
which MILNET X.25 addresses may be derived from addresses in the NIC
host table format.

A NIC host table address consists of the ASCII text string
representations of four decimal numbers separated by periods,
corresponding to the four octeted of a thirty-two bit Internet
address.  The four decimal numbers are referred to in this section as
"n", "h' "l", and "i".  Thus, a host table address may be represented
as: "n.h.l.i".  Each of these four numbers will have either one, two,
or three decimal digits and will never have a value greater than 255.
For example, in the host table, address: "10.2.0.124", n=10, h=2, l=0,
and i=124.  To convert a host table address to a MILNET X.25 address:

1.  If h < 64, the host table address corresponds to the X.25
physical address:


ZZZZ F IIIHHZZ (SS)

where:

     ZZZZ = 0000    as required

     F = 0          because the address is a physical address;

     III            is a three decimal digit respresentation of
                    "i", right-adjusted and padded with leading
                    zeros if required;

     HH             is a two decimal digit representation of "h",
                    right-adjusted and padded with leading zeros
                    if required;

     ZZ = 00        and

     (SS)           is optional
                    

In the example given above, the host table address 10.2.0.124
corresponds to the X.25 physical address 000001240200.

2.  If h > 64 or h = 64, the host table address corresponds to the
X.25 logical address


ZZZZ F RRRRRZZ (SS)

where:

     ZZZZ = 0000    as required

     F = 1          because the address is a logical address;

     RRRRR          is a five decimal digit representation of 
                    the result "r" of the calculation

                             r = h * 256 + i

                    (Note that the decimal representation of
                    "r" will always require five digits);

     ZZ = 00        and

     (SS)           is optional

Thus, the host table address 10.83.0.207 corresponds to the X.25
logical address 000012145500.

In both cases, the "n" and "l" fields of the host table address are
not used.


REFERENCES

[BBN1822] BBN, "Specifications for the Interconnection of a Host and
          an IMP", Report 1822, Bolt Beranek and Newman, Cambridge,
          Massachusetts, revised, December 1981.

[ETHERNET] "The Ethernet, A Local Area Network: Data Link Layer and
           Physical Layer Specification", AA-K759B-TK, Digital
           Equipment Corporation, Maynard, MA.  Also as: "The Ethernet
           - A Local Area Network", Version 1.0, Digital Equipment
           Corporation, Intel Corporation, Xerox Corporation,
           September 1980.  And: "The Ethernet, A Local Area Network:
           Data Link Layer and Physical Layer Specifications",
           Digital, Intel and Xerox, November 1982.  And: XEROX, "The
           Ethernet, A Local Area Network: Data Link Layer and
           Physical Layer Specification", X3T51/80-50, Xerox
           Corporation, Stamford, CT., October 1980.

[PUP] Boggs, D., J. Shoch, E. Taft, and R. Metcalfe, "PUP: An
      Internetwork Architecture", XEROX Palo Alto Research Center,
      CSL-79-10, July 1979; also in IEEE Transactions on
      Communication, Volume COM-28, Number 4, April 1980.

[RFC791] Postel, J., ed., "Internet Protocol - DARPA Internet Program
         Protocol Specification", STD 5, RFC 791, USC/Information
         Sciences Institute, September 1981.

[RFC878] Malis, Andrew, "The ARPANET 1822L Host Access Protocol", 
         RFC 878, BBN Communications Corp., December 1983.

[RFC926] International Standards Organization, "Protocol for Providing
         the Connectionless-Mode Network Services", RFC 926, ISO,
         December 1984.

[RFC1005] Khanna, A., and A. Malis, "The ARPANET AHIP-E Host Access
          Protocol (Enhanced AHIP)", RFC 1005, BBN Communications
          Corp., May 1987. 


PEOPLE

[DM28] Dennis Morris  <Morrisd@IMO-UVAX.DCA.MIL>

[JBP] Jon Postel <postel@isi.edu>

[JBW1] Joseph Walters, Jr. <JWalters@BBN.COM>

[JGH] Jim Herman <Herman@CCJ.BBN.COM>

[MB] Michael Brescia <Brescia@CCV.BBN.COM>

[RXM] Robert Myhill <Myhill@CCS.BBN.COM>

[XEROX] Fonda Pallone <---none--->

[]