SCION Registry: ISD and SCION AS assignments
In SCION, Isolation Domains (ISDs) and Autonomous System (AS) numbers are identified by globally unique numbers. These numbers are assigned and registered by the SCION Registry operated by the SCION Association under the governance of the Registry Committee, and in accordance with the Registry Policy.
ISD and SCION AS numbers may be requested, registered and managed using the SCION Registry portal – which will go live soon.
ISD NUMBER ASSIGNMENTS
ISDs are logical groups of SCION ASes under a common jurisdiction and with a uniform trust environment. ISDs are identified with 16-bit numbers that must be globally unique.
A SCION network must be a member of at least one ISD although may be members of more than one. ISDs are typically established on behalf of geopolitical jurisdictions (e.g. countries and territories), specific industry sectors, service providers, or governments so will normally only need to be requested and assigned to organisations managing these groups. The administrator(s) of the ISD are also responsible for creating a Trusted Root Configuration (TRC) to authenticate the members of the ISD, and this must be lodged with the SCION Registry.
ISD numbers are represented in decimal notation.
| ISD | Size | Description |
|---|---|---|
| 0 | 1 | The wildcard ISD |
| 1 - 15 | 16 | Reserved for documentation and sample code (analogous to RFC 5398) |
| 16 - 63 | 48 | Private use (analogous to RFC 6996) Can be used for testing and private deployments |
| 64 - 4095 | 4032 | Public ISDs (currently assigned by Anapaya) |
| 4096 - 65535 | 61440 | Reserved for future use |
SCION AS number assignments
Each SCION network is required to have a 48-bit number which is recommended to be globally unique in case the network joins more than one ISD.
Although they play a similar role, there is no relationship between SCION AS numbers and BGP ASNs as defined by RFC4271. However, in accordance with the Registry Policy, a network may only be assigned a number from the range 1 to 4,294,967,295 if they are the holder of the equivalent BGP ASN as verifiable in the AFRINIC, APNIC, ARIN, LACNIC or RIPE NCC databases.
Other assignments will be in accordance with the table below. The minimum assignment block will be 16 numbers (4 bits), but larger blocks up to 65,535 (16 bits) may be requested with a valid use case and upon payment of applicable fees.
SCION AS numbers should be represented in hexadecimal notation, although numbers in the lowest 32-bit range (0-4294967295) may be represented in decimal notation.
| SCION AS | Size | Description |
|---|---|---|
| 0:0:0 | 1 | The wildcard AS |
| 0:0:1 - 0:ffff:ffff | 4294967295 | Public SCION ASes (currently assigned by Anapaya). Proposed to be used for mapping to Internet ASNs |
| 1:0:0 - 1:ffff:ffff | 4294967296 | Reserved for future use |
| 2:0:0 - 2:ffff:ffff | 4294967296 | Public SCION ASes (currently assigned by Anapaya) |
| 3:0:0 - feff:ffff:ffff | 280362580180992 | Reserved for future use |
| ff00:0:0 - ff00:0:ffff | 65536 | Reserved for documentation and sample code (analogous to RFC 5398) |
| ffaa:0:0 - ffaa:00ff:ffff | 16777216 | Reserved for private use (analogous to RFC 6996) Can be used for testing/private deployments |
| ffaa:0100:0 - ffff:ffff:fffe | 369350410239 | Reserved for future use |
| ffff:ffff:ffff | 1 | Reserved |
FEES
ISD and SCION AS numbers are subject to a sign-up fee and recurring annual fees, with the following exceptions:
– Registrants who are members of the SCION Association in the Supporter, Community and Adopter categories are exempt from sign-up fees, and are exempt from recurring annual fees whilst they remain as a member of one of these categories.
– Registrants holding ISD and/or SCION AS numbers registered before 1 July 2026 are exempt from annual fees.
– Requests for ISD and/or SCION AS numbers between 1 July and 31 December 2026 will only incur the sign-up fee (which is only payable from 1 January 2027) and will not be charged the annual fee for the first year of registration.
| Resource | Sign-up fee | Annual fee |
|---|---|---|
| ISD number (1 number) | CHF 2,000 | CHF 1,000 |
| SCION AS number in range 1-4294967295 (1 number) | CHF 200 | CHF 100 |
| SCION AS block in range 2:0:0-2:ffff:ffff (16 numbers) | CHF 400 | CHF 200 |
| SCION AS block in range 2:0:0-2:ffff:ffff (256 numbers) | CHF 800 | CHF 400 |
| SCION AS block in range 2:0:0-2:ffff:ffff (65,535 numbers) | CHF 1,600 | CHF 800 |