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IETF RFC 982
Guidelines for the specification of the structure of the Domain Specific Part (DSP) of the ISO standard NSAP address
Last modified on Wednesday, April 9th, 1986
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Network Working Group ANSI
Request for Comments: 982 April 1986
Guidelines for the Specification of the Structure of the
Domain Specific Part (DSP) of the ISO Standard NSAP Address
ANSI Working Document X3S3.3/85-258
 Status of This Memo
The following is a RFC edition of the ANSI "Guidelines for the
Specification of the Structure of the Domain Specific Part (DSP) of
the ISO Standard NSAP Address". It should be understood that this
ANSI working document is in a draft state and subject to change.
These Guidelines are an important prerequirement to allow IP
addressing within the ISO connectionless protocol (CLNS), which
itself is necessary to allow the coexistance of the IP and the CLNS
in the Arpanet attached gateways.
A RFC to specify a suitable IP addressing method for ISOgrams is
currently worked on in Internet Task Forces and should be expected as
an RFC shortly.
This RFC is for informational purposes only and it's distribution
is unlimited. It does not specify a standard for the Arpa-Internet.
Hans-Werner Braun (HWB@GW.UMICH.EDU)
University of Michigan
ANSI PAGE 1 
RFC 982 April 1986
ANSI Guidelines
TITLE: GUIDELINES FOR THE SPECIFICATION OF THE STRUCTURE OF THE
DOMAIN SPECIFIC PART (DSP) OF THE ISO STANDARD NSAP ADDRESS
STATUS: X3S3.3 WORKING DRAFT
Introduction
There is a substantial amount of interest in providing guidance to
private address administration authorities on preferred formats and
semantics for the Domain Specific Part (DSP) of an NSAP address. In
particular it is felt that use of a limited number of preferred DSP
formats would allow organizations to easily use intermediate and end
systems from a variety of suppliers. This technical report specifies
the way in which the DSP may be constructed so as to facilitate
efficient address assignment.
1. Scope and Field of Application
This Technical Report specifies a recommended syntax and
interpretation for the Domain Specific Part of an NSAP address. NSAP
Address Administration Authorities are urged to use this format when
the equipment comprising an addressing domain is of a heterogeneous
nature.
2. References
ISO 6523 Data Interchange - Structure for the
identification of Organizations
ISO 7498 Information Processing Systems - Open Systems
Interconnection - Basic Reference Model
ISO 8348 Information Processing Systems - Data
Communications - Network Service Definition
ISO DIS 8348/DAD2 Information Processing Systems - Data
Communications - Addendum to the Network
Service Definition Covering Network Layer
Addressing
ISO DIS 8802 Information Processing Systems - Data
Communications - Local Area Networks
ECMA TR/20 Layer 4 to 1 Addressing
ANSI PAGE 2
RFC 982 April 1986
ANSI Guidelines
3. Definitions
(This section to be suppled)
4. Abbreviations
(This section to be supplied)
5. Addressing Principles
This section provides a summary of the major points contained in DIS
8348/DAD2, as they are relevant to this technical report.
Network addresses are defined to be hierarchical. An authority may
either assign a complete address, or else may identify a subdomain of
its own addressing domain within which addresses may be further
assigned by an identified authority for the subdomain. This is done
in such a way that all addresses are unique.
When an authority identifies a subdomain, this creates in effect a
prefix which applies to all addresses assigned within the subdomain.
Certain methods of assigning authority are recognized within the body
of DIS 8348/DAD 2. These take account of existing addressing
standards such as X.121. The abstract structure of an address is
shown in Figure 1.
ANSI PAGE 3
RFC 982 April 1986
ANSI Guidelines
+---------------------------+---------------------------+
I I I
I I D P I D S P I
I I I
+---------------------------+---------------------------+
: :
: :
V V
+-----+---------------------+
I I I
I AFI I I D I I
I I I
+-----+---------------------+
Figure 1: NSAP Address Structure
The components of this structure are as follows.
IDP: Initial Domain Part
This is the part of the address whose entire content is
standardized. It consists of two parts, the AFI and the IDI.
AFI: Authority and Format Identifier
This specifies the format of the IDI, the authority responsible
for allocating IDI values, and the syntax of the DSP.
IDI: Initial Domain Identifier
This identifies the subdomain from which DSP values are allocated,
and the authority responsible for allocating the values.
DSP: Domain Specific Part
The contents and semantics of the DSP are not specified in DIS
8348/DAD2. Its abstract syntax is however defined by the AFI. In
most cases, this means that the DSP abstract syntax can be either
binary or decimal.
IDI formats specified in DIS 8348/DAD2 identify a number of
authorities for IDI allocation. These are:
1. X.121 (Public data network numbering)
2. F.69 (Telex numbering)
ANSI PAGE 4
RFC 982 April 1986
ANSI Guidelines
3. E.163 (Telephone numbering)
4. E.164 (ISDN numbering)
5. ISO DCC (Geographical address assignment under ISO authority.
A subset of the DCC values used in X.121 have been used to
designate the national addressing authorities)
6. ISO 6523-ICD (Non-geographic address assignment under ISO
authority, using the International Code Designators according
to ISO 6523)
7. Local (the IDI is null and the entire address is contained in
the DSP).
6. Analysis
(This section to be supplied)
7. Recommendations
7.1 X.121 DSP format guidelines
Description of Binary syntax
The length of the DSP can be determined since the total address
length is known, and the IDP has fixed length for any given AFI
value. If DSP is present, a DSP of 2 or less octets is an NSAP
selector. A DSP between 3 and 9 octets is interpreted in the
manner described below.
The length of the subnetwork identification is fixed at two
octets (16 bits). The assignment of subnetwork
identifications is under the control of the administering
authority for the private domain, except that the value with
both octets hex "FF" is reserved to indicate that the
subnetwork is not explicitly identified.
The length of the subnetwork address may be up to six octets,
and is determined by the DSP length minus three octets. For
subnetworks using DIS 8802 MAC addressing, this field consists
of the octets of the MAC address in the same order as they are
defined in DIS 8802.
The NSAP selector occupies a single octet.
ANSI PAGE 5
RFC 982 April 1986
ANSI Guidelines
Description of Decimal syntax
The length of the DSP can be determined since the total address
length is known, and the IDP has fixed length for any given AFI
value. If DSP is present, a DSP of 8 or less decimal digits is
an NSAP selector. A DSP between 8 and 23 decimal digits is
interpreted in the manner described below.
The length of the subnetwork identification is fixed at five
decimal digits. The assignment of subnetwork identifications
is under the control of the administering authority for the
private domain, except that a value of "99999" is reserved to
indicate that the subnetwork is not explicitly identified.
The length of the subnetwork address may be up to fifteen
decimal digits, and is determined by the DSP length minus eight
decimal digits.
The NSAP selector occupies three decimal digits.
7.2 ISO DCC DSP format guidelines
Description of Binary syntax
The length of the DSP can be determined since the total address
length is known, and the IDP has fixed length for any given AFI
value. The length of the DSP is between 6 and 12 octets.
The first three octets identify an organization which has been
designated as an addressing authority. This authority is
responsible for assigning values to the remainder of the DSP.
The length of the subnetwork identification is fixed at two
octets (16 bits). The assignment of subnetwork identifications
is under the control of the administering authority for the
private domain, except that the value with both octets hex "FF"
is reserved to indicate that the subnetwork is not explicitly
identified.
The length of the subnetwork address may be up to six octets,
and is determined by the DSP length minus three octets. For
subnetworks using DIS 8802 MAC addressing, this field consists
of the octets of the MAC address in the same order as they are
defined in DIS 8802.
The NSAP selector occupies a single octet.
ANSI PAGE 6
RFC 982 April 1986
ANSI Guidelines
Description of Decimal syntax
The length of the DSP can be determined since the total address
length is known, and the IDP has fixed length for any given AFI
value. The length of the DSP is between 14 and 29 decimal
digits.
The first six digits identify an organization which as been
designated as an addressing authority. This authority is
responsible for assigning values to the remainder of the DSP.
The length of the subnetwork identification is fixed at five
decimal digits. The assignment of subnetwork identifications
is under the control of the administering authority for the
private domain, except that a value of "99999" is reserved to
indicate that the subnetwork is not explicitly identified.
The length of the subnetwork address may be up to fifteen
decimal digits, and is determined by the DSP length minus eight
decimal digits.
The NSAP selector occupies three decimal digits.
7.3 F.69 DSP format guidelines
Description of Binary syntax
The length of the DSP can be determined since the total address
length is known, and the IDP has fixed length for any given AFI
value. If DSP is present, a DSP of 2 or less octets is an NSAP
selector. A DSP between 3 and 9 octets is interpreted in the
manner described below. Interpretation of a DSP greater than 9
octets in length is not specified in this report.
The length of the subnetwork identification is fixed at two
octets (16 bits). The assignment of subnetwork identifications
is under the control of the administering authority for the
private domain, except that the value with both octets hex "FF"
is reserved to indicate that the subnetwork is not explicitly
identified.
The length of the subnetwork address may be up to six octets,
and is determined by the DSP length minus three octets. For
subnetworks using DIS 8802 MAC addressing, this field consists
of the octets of the MAC address in the same order as they are
defined in DIS 8802.
ANSI PAGE 7
RFC 982 April 1986
ANSI Guidelines
The NSAP selector occupies a single octet.
Description of Decimal syntax
The length of the DSP can be determined since the total address
length is known, and the IDP has fixed length for any given AFI
value. If DSP is present, a DSP of 8 or less decimal digits is
an NSAP selector. A DSP between 8 and 23 decimal digits is
interpreted in the manner described below. Interpretation of a
DSP greater than 23 decimal digits in length is not specified
in this report.
The length of the subnetwork identification is fixed at five
decimal digits. The assignment of subnetwork identifications
is under the control of the administering authority for the
private domain, except that a value of "99999" is reserved to
indicate that the subnetwork is not explicitly identified.
The length of the subnetwork address may be up to fifteen
decimal digits, and is determined by the DSP length minute
eight decimal digits.
The NSAP selector occupies three decimal digits.
7.4 E.163 DSP format guidelines
Description of Binary syntax
The length of the DSP can be determined since the total address
length is known, and the IDP has fixed length for any given AFI
value. If DSP is present, a DSP of 2 or less octets is an NSAP
selector. A DSP between 3 and 9 octets is interpreted in the
manner described below. Interpretation of a DSP greater than 9
octets in length is not specified in this report.
The length of the subnetwork identification is fixed at two
octets (16 bits). The assignment of subnetwork identifications
is under the control of the administering authority for the
private domain, except that the value with both octets hex "FF"
is reserved to indicate that the subnetwork is not explicitly
identified.
The length of the subnetwork address may be up to six octets,
and is determined by the DSP length minus three octets. For
subnetworks using DIS 8802 MAC addressing, this field consists
of the octets of the MAC address in the same order as they are
defined in DIS 8802.
ANSI PAGE 8
RFC 982 April 1986
ANSI Guidelines
The NSAP selector occupies a single octet.
Description of Decimal syntax
The length of the DSP can be determined since the total address
length is known, and the IDP has fixed length for any given AFI
value. If DSP is present, a DSP of 8 or less decimal digits is
an NSAP selector. A DSP between 8 and 23 decimal digits is
interpreted in the manner described below. Interpretation of a
DSP greater than 23 decimal digits in length is not specified
in this report.
The length of the subnetwork identification is fixed at five
decimal digits. The assignment of subnetwork identifications
is under the control of the administering authority for the
private domain, except that a value of "99999" is reserved to
indicate that the subnetwork is not explicitly identified.
The length of the subnetwork address may be up to fifteen
decimal digits, and is determined by the DSP length minus eight
decimal digits.
The NSAP selector occupies three decimal digits.
7.5 E.164 DSP format guidelines
Description of Binary syntax
The length of the DSP can be determined since the total address
length is known, and the IDP has fixed length for any given AFI
value. If DSP is present, a DSP of 2 or less octets is an NSAP
selector. A DSP between 3 and 9 octets is interpreted in the
manner described below. Interpretation of a DSP greater than 9
octets in length is not specified in this report.
The length of the subnetwork identification is fixed at two
octets (16 bits). The assignment of subnetwork identifications
is under the control of the administering authority for the
private domain, except that the value with both octets hex "FF"
is reserved to indicate that the subnetwork is not explicitly
identified.
The length of the subnetwork address may be up to six octets,
and is determined by the DSP length minus three octets. For
subnetworks using DIS 8802 MAC addressing, this field consists
of the octets of the MAC address in the same order as they are
defined in DIS 8802.
ANSI PAGE 9
RFC 982 April 1986
ANSI Guidelines
The NSAP selector occupies a single octet.
Description of Decimal syntax
The length of the DSP can be determined since the total address
length is known, and the IDP has fixed length for any given AFI
value. If DSP is present, a DSP of 8 or less decimal digits is
an NSAP selector. A DSP between 8 and 23 decimal digits is
interpreted in the manner described below. Interpretation of a
DSP greater than 23 decimal digits in length is not specified
in this report.
The length of the subnetwork identification is fixed at five
decimal digits. The assignment of subnetwork identifications
is under the control of the administering authority for the
private domain, except that a value of "99999" is reserved to
indicate that the subnetwork is not explicitly identified.
The length of the subnetwork address may be up to fifteen
decimal digits, and is determined by the DSP length minus eight
decimal digits.
The NSAP selector occupies three decimal digits.
7.6 ISO 6523-ICD DSP format guidelines
Description of Binary syntax
The length of the DSP can be determined since the total address
length is known, and the IDP has fixed length for any given AFI
value. The length of the DSP is between 5 and 11 octets.
The first two octets identify an organization which has been
designated as an addressing authority. This authority is
responsible for assigning values to the remainder of the DSP.
The length of the subnetwork identification is fixed at two
octets (16 bits). The assignment of subnetwork identifications
is under the control of the administering authority for the
private domain, except that the value with both octets hex "FF"
is reserved to indicate that the subnetwork is not explicitly
identified.
The length of the subnetwork address may be up to six octets,
and is determined by the DSP length minus three octets. For
ANSI PAGE 10
RFC 982 April 1986
ANSI Guidelines
subnetworks using DIS 8802 MAC addressing, this field consists
of the octets of the MAC address in the same order as they are
defined in DIS 8802.
The NSAP selector occupies a single octet.
Description of Decimal syntax
The length of the DSP can be determined since the total address
length is known, and the IDP has fixed length for any given AFI
value. The length of the DSP is between 12 and 27 decimal
digits.
The first four digits identify an organization which has been
designated as an addressing authority. This authority is
responsible for assigning values to the remainder of the DSP.
The length of the subnetwork identification is fixed at five
decimal digits. The assignment of subnetwork identifications
is under the control of the administering authority for the
private domain, except that a value of "99999" is reserved to
indicate that the subnetwork is not explicitly identified.
The length of the subnetwork address may be up to fifteen
decimal digits, and is determined by the DSP length minus eight
decimal digits.
The NSAP selector occupies three decimal digits.
7.7 Local DSP format guidelines
No recommendations made.
ANSI PAGE 11
Guidelines for the specification of the structure of the Domain Specific Part (DSP) of the ISO standard NSAP address
RFC TOTAL SIZE: 21969 bytes
PUBLICATION DATE: Wednesday, April 9th, 1986
LEGAL RIGHTS: The IETF Trust (see BCP 78)
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