Browse Prior Art Database

Intersystem Unique Host Identifiers

IP.com Disclosure Number: IPCOM000051432D
Original Publication Date: 1981-Jan-01
Included in the Prior Art Database: 2005-Feb-10
Document File: 2 page(s) / 25K

Publishing Venue

IBM

Related People

Wanish, PJ: AUTHOR

Abstract

In environments where operating systems must communicate, each must hav its own unique name or identifier (ID). To avoid duplicates, and the associated ambiguities, a computer algorithm is required to define a value which will not recur under normal conditions.

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Intersystem Unique Host Identifiers

In environments where operating systems must communicate, each must hav its own unique name or identifier (ID). To avoid duplicates, and the associated ambiguities, a computer algorithm is required to define a value which will not recur under normal conditions.

Previous attempts at automatically defining a host ID have failed because they merely associated the machine ID with the host. In multi-processor (MP) environments, this method can produce the same ID in different operating systems. Since uniqueness is essential, something besides the machine serial number must be used.

The following provides an ID which is 11 bytes long and which consists of four fields. The first field, which has two bytes, contains the data stored by the STORE CPU ADDRESS (STAP) instruction for the IBM System/370. If the multiprocessing feature is not installed, this field is set to zero. The next two fields are obtained from the STORE CPU ID (STIDP) instruction. The three-byte CPU identification number and the two-byte model number are used. The fourth field contains the first word of the time-of-day clock, as stored by the STORE CLOCK (STCK) instruction. A standard epoch of January 1, 1900, 0 A.M. Greenwich Mean Time, is assumed. The storage format is shown in the following table. See Original.

The CPU address is necessary in the host ID because new CPUs may have one machine identification number for multiple processors. Today, the identification number and model number are unique to a processor.

The first half of the time-of-day (TOD) clock is unique, to an accuracy of...