RFC 982

Guidelines for the specification of the structure of the Domain Specific Part (DSP) of the ISO standard NSAP address

📅 published April 1986, from ietf

RFC 982 💖 Guidelines for the Specification of the Structure of the Domain Specific Part (DSP) of the ISO Standard NSAP Address

okay bestie, this one is RFC 982 from April 1986 🦋. It's from the Network Working Group, and the content comes from ANSI as ANSI Working Document X3S3.3/85-258. The status is X3S3.3 working draft, so it's still a draft. It's informational, not a standard. It doesn't list anything it obsoletes or updates. The RFC edition was written by Hans-Werner Braun (HWB@GW.UMICH.EDU) from the University of Michigan 🌸

Status of This Memo ✨

so this section is giving honesty 💅. The RFC is an RFC edition of the ANSI "Guidelines for the Specification of the Structure of the Domain Specific Part (DSP) of the ISO Standard NSAP Address". The ANSI doc is a draft and it can change, so don't get too attached yet 🙈

these guidelines are a must-have prerequirement for IP addressing inside the ISO connectionless protocol (CLNS). CLNS is what lets IP and CLNS coexist on the Arpanet-attached gateways, so it's a big deal 💜

there's an IP addressing method for ISOgrams being worked on in the Internet Task Forces, and it should show up as an RFC soon 🧚

this RFC is for informational purposes only, its distribution is unlimited, and it does not specify a standard for the Arpa-Internet 🎀

Introduction

there's a lot of interest in giving address admin authorities guidance on preferred formats and semantics for the Domain Specific Part (DSP) of an NSAP address 👑 the vibe is that a small set of preferred DSP formats would let organizations use intermediate and end systems from different suppliers without drama 🫶

this technical report explains how the DSP can be built so address assignment is efficient 🍓

1. Scope and Field of Application ✨

this technical report describes 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 in an addressing domain is heterogeneous (aka a mix of different stuff) 💖

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

3. Definitions 🌈

(This section to be suppled)

4. Abbreviations 🎀

(This section to be supplied)

5. Addressing Principles 💜

this section is a quick summary of the big points in DIS 8348/DAD2 that matter for this report 🦋

network addresses are hierarchical. an authority can either assign a complete address, or identify a subdomain of its own addressing domain, where addresses can be assigned further by an authority identified for that subdomain. it's set up so all addresses are unique 🔥

when an authority identifies a subdomain, that effectively creates a prefix that applies to every address assigned inside the subdomain 🌸

DIS 8348/DAD 2 recognizes certain ways of assigning authority, and they take existing addressing standards like X.121 into account. the abstract structure of an address is shown in Figure 1 ✨

   +---------------------------+---------------------------+
   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

here's how the pieces work 🧚

IDP: Initial Domain Part
- this is the part of the address whose entire content is standardized. it has 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 that DSP values are allocated from, and the authority responsible for allocating those values.
DSP: Domain Specific Part
- the contents and semantics of the DSP are not specified in DIS 8348/DAD2. its abstract syntax is defined by the AFI. in most cases, that means the DSP abstract syntax can be either binary or decimal 💅

IDI formats in DIS 8348/DAD2 identify a number of authorities for IDI allocation. they are:

X.121 (Public data network numbering)
F.69 (Telex numbering)
E.163 (Telephone numbering)
E.164 (ISDN numbering)
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)
ISO 6523-ICD (Non-geographic address assignment under ISO authority, using the International Code Designators according to ISO 6523)
Local (the IDI is null and the entire address is contained in the DSP) 🌟

6. Analysis 🔮

(This section to be supplied)

7. Recommendations 🎀

the main event is here, bestie. this section has the format guidelines 🫶

7.1. X.121 DSP format guidelines 💖

Description of Binary syntax

the length of the DSP can be figured out because the total address length is known, and the IDP has a fixed length for any given AFI value. if a DSP is present, a DSP of 2 or less octets is an NSAP selector. a DSP between 3 and 9 octets is read the way described below 🦋

the subnetwork identification is fixed at two octets (16 bits). the administering authority for the private domain controls how subnetwork identifications are assigned, except that the value with both octets hex FF is reserved to show that the subnetwork is not explicitly identified 🌸

the subnetwork address can be up to six octets, and its length is the DSP length minus three octets. for subnetworks that use DIS 8802 MAC addressing, this field holds the octets of the MAC address in the same order they're defined in DIS 8802 ✨

the NSAP selector takes up a single octet 💜

Description of Decimal syntax

the length of the DSP can be figured out because the total address length is known, and the IDP has a fixed length for any given AFI value. if a DSP is present, a DSP of 8 or less decimal digits is an NSAP selector. a DSP between 8 and 23 decimal digits is read the way described below 🧚

the subnetwork identification is fixed at five decimal digits. the administering authority for the private domain controls how subnetwork identifications are assigned, except that the value "99999" is reserved to show that the subnetwork is not explicitly identified 🌈

the subnetwork address can be up to fifteen decimal digits, and its length is the DSP length minus eight decimal digits 🔥

the NSAP selector takes up three decimal digits 👑

7.2. ISO DCC DSP format guidelines 🍓

Description of Binary syntax

the length of the DSP can be figured out because the total address length is known, and the IDP has a 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 that has been designated as an addressing authority. that authority is responsible for assigning values to the rest of the DSP 💅

the NSAP selector takes up a single octet 💜

Description of Decimal syntax

the length of the DSP can be figured out because the total address length is known, and the IDP has a 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 that has been designated as an addressing authority. that authority is responsible for assigning values to the rest of the DSP 🌟

the subnetwork address can be up to fifteen decimal digits, and its length is the DSP length minus eight decimal digits 🔥

the NSAP selector takes up three decimal digits 👑

7.3. F.69 DSP format guidelines 🎀

Description of Binary syntax

that's part 1 of the tea, bestie 🫶 part 2 picks up right where we left off in 7.3 so stay tuned 💜✨

So the NSAP selector is just one octet 🍓 that's the whole selector, bestie.

Description of Decimal syntax

Okay, so the DSP length can be figured out because the total address length is known, and the IDP has a fixed length for any given AFI value. ✨ If a DSP is present, a DSP of 8 or less decimal digits is an NSAP selector. A DSP between 8 and 23 decimal digits gets interpreted the way we describe below. A DSP longer than 23 decimal digits is not specified in this report 🦋

The subnetwork identification is always five decimal digits long 💖 Assigning those is up to the administering authority for the private domain, except that "99999" is reserved to mean the subnetwork is not explicitly identified. 🌸

The subnetwork address can be up to fifteen decimal digits, and its length 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 DSP length is still something you can work out, since the total address length is known and the IDP has a fixed length for any given AFI value. 💅 If a DSP is present, a DSP of 2 or less octets is an NSAP selector. A DSP between 3 and 9 octets is interpreted as described below. Anything bigger than 9 octets is not specified in this report 🎀

The subnetwork identification is fixed at two octets (16 bits). Assignment 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 subnetwork address can be up to six octets, and its length 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. 💜

Description of Decimal syntax

The DSP length can be determined since the total address length is known, and the IDP has a fixed length for any given AFI value. 🦋 If a 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. A DSP greater than 23 decimal digits in length is not specified in this report 😭

The subnetwork identification is fixed at five decimal digits. Assignment is under the control of the administering authority for the private domain, except that "99999" is reserved to indicate that the subnetwork is not explicitly identified. 💖

The subnetwork address can 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 DSP length can be determined since the total address length is known, and the IDP has a fixed length for any given AFI value. 💅 If a 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. A DSP greater than 9 octets in length is not specified in this report 🎀

The subnetwork address can 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. 💜

Description of Decimal syntax

The subnetwork address can 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 DSP length can be determined since the total address length is known, and the IDP has a 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 NSAP selector occupies a single octet. 🦋

Description of Decimal syntax

The DSP length can be determined since the total address length is known, and the IDP has a 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 subnetwork address can 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. 🫶

📦 where this page comes from

ietf: rfc982 1986-04
💖 girlified by claude-haiku-5-5 on 2026-10-19: a language model's rewrite of the original, under its terms