Milnet Parameters

Last Updated

• 2011-06-10

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Milnet Link Numbers

Registration Procedure(s)

• Registry closed

Note

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

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.

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• CSV

Milnet Logical Addresses

Registration Procedure(s)

• Registry closed

Note

The MILNET facility for "logical addressing" is described in RFC 878 and RFC 1005. 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.

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Milnet X.25 Address Mappings

Registration Procedure(s)

• Registry closed

Note

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.