| Internet-Draft | ASN Prefix-based Addressing for IPv6 | November 2025 |
| Kristoff | Expires 30 May 2026 | [Page] |
This document describes a method and policy for ASN prefix-based addressing for IPv6.¶
This Internet-Draft is submitted in full conformance with the provisions of BCP 78 and BCP 79.¶
Internet-Drafts are working documents of the Internet Engineering Task Force (IETF). Note that other groups may also distribute working documents as Internet-Drafts. The list of current Internet-Drafts is at https://datatracker.ietf.org/drafts/current/.¶
Internet-Drafts are draft documents valid for a maximum of six months and may be updated, replaced, or obsoleted by other documents at any time. It is inappropriate to use Internet-Drafts as reference material or to cite them other than as "work in progress."¶
This Internet-Draft will expire on 30 May 2026.¶
Copyright (c) 2025 IETF Trust and the persons identified as the document authors. All rights reserved.¶
This document is subject to BCP 78 and the IETF Trust's Legal Provisions Relating to IETF Documents (https://trustee.ietf.org/license-info) in effect on the date of publication of this document. Please review these documents carefully, as they describe your rights and restrictions with respect to this document. Code Components extracted from this document must include Revised BSD License text as described in Section 4.e of the Trust Legal Provisions and are provided without warranty as described in the Revised BSD License.¶
This document defines an address allocation system (called "APbA") whereby an Autonomous System (AS) number is embedded as sub-prefix bits of an IPv6 address, resulting in approximately 1.2 quintillion addresses per AS. Advantages of this mechanism include the ability to get allocate AS-specific and unique address space without an allocation protocol or registration process. This system also makes it easy to determine an association between AS and address, which is useful for debugging and auditing purposes.¶
This mechanism draws inspiration from [RFC3180]. Unlike that earlier specification however, this system applies specifically to unicast addressing, supports 32-bit ASNs, and provides significantly more addresses per AS. Some administrative challenges identified by [RFC6034] remain and questions about the integration into modern technology such as [RFC6482] are addressed later in this document.¶
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in BCP 14 [RFC2119] [RFC8174] when, and only when, they appear in all capitals, as shown here.¶
An IPv6 address with the prefix [IANA-assigned 16-bit prefix] indicates that the adress is a APbA address. The embedded AS follows as a sub-prefix. A 16-bit AS is left-padded with 0s. The remaining 96-bit suffix bits are locally significant and defined by the corresponding AS.¶
Bits: | 0 thru 15 | 16 thru 47 | 48 thru 127 |
+------+---------------+-------------------+--------+
Value: | [TBD] | 16 or 32 bit ASN | Locally Assigned |
+------+---------------+-------------------+--------+
¶
Consider, for example AS 64496. Written in hex, we get an IPv6 prefix of 3fff:0:fbf0::/48.¶
AS numbers may be reserved for private or special use. They may also be unallocated. These AS designations MUST be maintained when mapped to APbA addresses, which may render these addresses unavailable or inappropriate for public use.¶
Internet registries SHOULD provide service functions and support for APdA addresses.¶
This memo requests a 16-bit IPv6 address prefix assignment from IANA.¶
APdA addresses SHOULD have corresponding ROAs [RFC6482] if externally and publicly routed on the Internet. Network operators MAY reject APdA route announcments otherwise.¶
The following individuals provided an array of feedback to help improve this document: Roland Dobbins. Any remaining errors or imperfections are the sole responsbility of the document authors.¶