2001-08-23 Registry closed 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. 0-63 BBNCC Monitoring 64-149 Unassigned 150 Xerox NS IDP "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. 151 Unassigned 152 PARC Universal Protocol 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. 153 TIP Status Reporting 154 TIP Accounting 155 Internet Protocol [regular] 156-158 Internet Protocol [experimental] 159 Figleaf Link 160 Blacker Local Network Protocol 161-194 Unassigned 195 ISO-IP 196-247 Experimental Protocols 248-255 Network Maintenance Registry closed The MILNET facility for "logical addressing" is described in and . 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. 0 Reserved 1 The BBN Core Gateways 2-254 Unassigned 255 Reserved Registry closed 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. Dennis Morris mailto:Morrisd&imo-uvax.dca.mil Fonda Pallone Jim Herman mailto:Herman&ccj.bbn.com Jon Postel mailto:postel&isi.edu Joseph Walters, Jr. mailto:JWalters&BBN.COM Michael Brescia mailto:Brescia&ccv.bbn.com Robert Myhill mailto:Myhill&ccs.bbn.com