The 'sustainability' Well-Known URI
draft-besleaga-green-sustainability-wellknown-01
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| Author | Andrei Nicolae BESLEAGA | ||
| Last updated | 2026-03-16 | ||
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draft-besleaga-green-sustainability-wellknown-01
GREEN A. N. Besleaga
Internet-Draft Independent
Intended status: Informational 16 March 2026
Expires: 17 September 2026
The 'sustainability' Well-Known URI
draft-besleaga-green-sustainability-wellknown-01
Abstract
This document defines the "sustainability" well-known URI. This URI
provides a standardized, out-of-band mechanism for web servers and
digital services to publish their aggregated environmental impact,
energy consumption, and carbon footprint metrics.
By utilizing an asynchronous reporting model, this approach allows
for transparent environmental accounting without the bandwidth and
energy overhead associated with per-request HTTP headers.
Status of This Memo
This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79.
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This Internet-Draft will expire on 17 September 2026.
Copyright Notice
Copyright (c) 2026 IETF Trust and the persons identified as the
document authors. All rights reserved.
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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
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provided without warranty as described in the Revised BSD License.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
1.1. Requirements Language . . . . . . . . . . . . . . . . . . 3
2. The "sustainability" Well-Known URI . . . . . . . . . . . . . 3
2.1. URI Definition . . . . . . . . . . . . . . . . . . . . . 3
2.2. Mandatory Minimum Supported Service . . . . . . . . . . . 3
2.3. Optional, Extended, Query Parameters . . . . . . . . . . 3
2.4. Payload Format . . . . . . . . . . . . . . . . . . . . . 4
2.4.1. Mandatory Response Fields . . . . . . . . . . . . . . 4
2.4.2. Optional Response Fields . . . . . . . . . . . . . . 5
2.4.3. Formal Definition (CDDL) . . . . . . . . . . . . . . 5
3. Example Usage . . . . . . . . . . . . . . . . . . . . . . . . 6
3.1. Basic Response (Root Request) . . . . . . . . . . . . . . 6
3.2. Yearly Trend (Monthly Granularity) . . . . . . . . . . . 6
3.3. Target-Specific Request . . . . . . . . . . . . . . . . . 6
3.4. Target Specific Quarterly Trend (Weekly Granularity) . . 7
4. Operational Considerations . . . . . . . . . . . . . . . . . 7
4.1. Caching . . . . . . . . . . . . . . . . . . . . . . . . . 7
5. Security Considerations . . . . . . . . . . . . . . . . . . . 7
5.1. Traffic Analysis . . . . . . . . . . . . . . . . . . . . 7
5.2. Array Size Limits . . . . . . . . . . . . . . . . . . . . 7
5.3. Hardware Fingerprinting . . . . . . . . . . . . . . . . . 8
5.4. Denial of Service (DoS) . . . . . . . . . . . . . . . . . 8
6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 8
7. References . . . . . . . . . . . . . . . . . . . . . . . . . 8
7.1. Normative References . . . . . . . . . . . . . . . . . . 8
7.2. Informative References . . . . . . . . . . . . . . . . . 9
Author's Address . . . . . . . . . . . . . . . . . . . . . . . . 9
1. Introduction
The digital economy consumes a significant and growing percentage of
global electricity. Emerging regulatory frameworks, such as the EU
Corporate Sustainability Reporting Directive (CSRD) [EU-CSRD],
industry standards like the Green Software Foundation's Software
Carbon Intensity [GSF-SCI] and the W3C Web Sustainability Guidelines
[W3C-WSG], increasingly require organizations to disclose the
environmental impact of their digital services.
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These transparency efforts align with the United Nations 2030 Agenda
for Sustainable Development [UN-SDG], specifically supporting energy
efficiency and sustainable infrastructure targets, encouraging
companies to integrate sustainability information into their
reporting cycles.
While initial proposals for carbon transparency focused on per-
request HTTP headers, such methods introduce a "rebound effect" where
metadata increases the carbon footprint of the transaction. This
document leverages [RFC8615] to define a /.well-known/sustainability
URI for out-of-band reporting.
1.1. Requirements Language
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.
2. The "sustainability" Well-Known URI
2.1. URI Definition
The URI suffix "sustainability" is registered in the Well-Known URI
Registry. A client requests metrics by issuing an HTTP GET request
to /.well-known/sustainability.
2.2. Mandatory Minimum Supported Service
A compliant server MUST support the following "Basic" service level:
* *No Parameters*: Requests to the root URI with no query strings.
* *Scope*: Metrics MUST represent the aggregate impact of the entire
host.
* *Default Period*: The server MUST return the most recently
completed full calendar month.
* *Format*: The server MUST return a single JSON object.
2.3. Optional, Extended, Query Parameters
Servers MAY support "Extended" capabilities via the following
parameters:
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* *target*: Specifies a resource path (e.g., ?target=/api/v1/
search).
* *period*: Specifies the timeframe using [RFC3339] formats:
- Yearly: YYYY
- Quarterly: YYYY-QX (e.g., 2026-Q1)
- Monthly: YYYY-MM
- Daily: YYYY-MM-DD
* *granularity*: Defines the "slices" within a period (monthly,
weekly, or daily). If granularity is finer than the period, the
server SHOULD return an array of objects.
2.4. Payload Format
A successful response MUST return a JSON object or an array of
objects [RFC8259] with the media type application/json.
2.4.1. Mandatory Response Fields
* *capabilities*: MUST be "basic" or "extended".
* *methodology-type*: Categorizes the data source. MUST be one of:
- hardware-metered: Direct capture via physical meters.
- hardware-estimated: Derived from hardware utilization models.
- cloud-billing: Derived from cloud provider carbon reports.
- third-party-modeled: Estimated via industry averages.
* *methodology-uri*: Link to the full methodology specification
(calculation methodology).
* *reporting-period*: The timeframe covered by the object.
* *energy-consumption*: A numerical value indicating the total
energy consumed by the host or resource during the reporting
period.
* *energy-unit*: A string indicating the unit of energy (MUST be one
of: Wh, kWh, MWh, or GWh).
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* *carbon-footprint*: Total impact in grams of CO2 equivalent.
* *carbon-unit*: A string indicating the unit of carbon measurement
(MUST be one of: gCO2e, kgCO2e, or mtCO2e).
2.4.2. Optional Response Fields
The JSON object MAY contain the following OPTIONAL keys to align with
the [GHG-PROTOCOL] and European Sustainability Reporting Standards
(ESRS E1):
* *target-path*: A string indicating the resource path requested as
target
* *carbon-accounting*: "location-based" or "market-based" (following
[GHG-PROTOCOL]).
* *scope-1*: A numerical value indicating the estimated Scope 1
(direct) carbon emissions.
* *scope-2*: A numerical value indicating the estimated Scope 2
(indirect/purchased energy) carbon emissions.
* *scope-3*: A numerical value indicating the estimated Scope 3
(value chain) carbon emissions.
* *sci-score*: A numerical value indicating the Software Carbon
Intensity (SCI) score [GSF-SCI].
2.4.3. Formal Definition (CDDL)
The following CDDL [RFC8949] describes the response:
```cddl ; Root response: Can be a single object or a list of objects
for trends sustainability-response = sustainability-metrics / [*
sustainability-metrics]
sustainability-metrics = { capabilities: "basic" / "extended",
; Mandatory methodology disclosure methodology-type: "hardware-
metered" / "hardware-estimated" / "cloud-billing" / "third-party-
modeled", methodology-uri: tstr,
; Timeframe of the report (RFC3339 formatted string) reporting-
period: tstr,
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; Energy metrics (Units are fixed as literals to ensure
interoperability) energy-consumption: number, energy-unit: "Wh" /
"kWh" / "MWh" / "GWh",
; Carbon metrics carbon-footprint: number, carbon-unit: "gCO2e" /
"kgCO2e" / "mtCO2e",
; Optional fields for extended capabilities ? carbon-accounting:
"location-based" / "market-based", ? target-path: tstr, ? scope-1:
number, ? scope-2: number, ? scope-3: number, ? sci-score: number }
```
3. Example Usage
3.1. Basic Response (Root Request)
GET /.well-known/sustainability
```json { "capabilities": "basic", "methodology-type": "cloud-
billing", "methodology-uri": "https://example.com/methodology",
"reporting-period": "2026-02", "energy-consumption": 1200.5, "energy-
unit": "kWh", "carbon-footprint": 340000, "carbon-unit": "gCO2e" }
```
3.2. Yearly Trend (Monthly Granularity)
GET /.well-known/sustainability?period=2025&granularity=monthly
```json [ { "reporting-period": "2025-01", "energy-consumption":
105.2}, { "reporting-period": "2025-02", "energy-consumption": 98.4}
]
```
3.3. Target-Specific Request
GET /.well-known/sustainability?target=/api/v1&period=2026-03-15
json { "capabilities": "extended", "methodology-type": "hardware-
estimated", "methodology-uri": "https://example.com/sustainability/
methodology", "reporting-period": "2026-03-15", "energy-consumption":
0.85, "energy-unit": "kWh", "carbon-footprint": 145, "carbon-unit":
"gCO2e", "target-path": "/api/v1" }
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3.4. Target Specific Quarterly Trend (Weekly Granularity)
GET /.well-known/sustainability?target=/api/
v1&period=2025-Q4&granularity=weekly
```json [ { "capabilities": "extended", "methodology-type":
"hardware-estimated", "methodology-uri":
"https://example.com/sustainability/methodology", "reporting-period":
"2025-W40", "energy-consumption": 102.5, "energy-unit": "kWh",
"carbon-footprint": 18500, "carbon-unit": "gCO2e", "target-path":
"/api/v1" }, { "capabilities": "extended", "methodology-type":
"hardware-estimated", "methodology-uri":
"https://example.com/sustainability/methodology", "reporting-period":
"2025-W41", "energy-consumption": 98.2, "energy-unit": "kWh",
"carbon-footprint": 17900, "carbon-unit": "gCO2e", "target-path":
"/api/v1" } ]
```
4. Operational Considerations
4.1. Caching
Because this endpoint may require internal database queries to
aggregate data - especially when dynamic period or other query
parameters are utilized - it could become a vector for Denial of
Service (DoS) attacks. Hosts SHOULD implement heavy caching (e.g.,
Cache-Control: max-age=86400) for the .well-known responses, and
enforce strict rate-limiting on requests containing time-range query
parameters. For historical reports, a long max-age (e.g., one year)
is RECOMMENDED.
5. Security Considerations
5.1. Traffic Analysis
Servers SHOULD NOT report metrics at a granularity finer than 24
hours to prevent correlating energy spikes with specific real-time
user actions. Real-time telemetry is NOT RECOMMENDED as it could
allow an attacker to correlate energy usage with real-time actions.
5.2. Array Size Limits
To prevent Denial of Service (DoS) via memory exhaustion, servers
supporting granularity MUST limit the maximum number of objects
returned. A cap of 366 objects is RECOMMENDED.
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5.3. Hardware Fingerprinting
Precise metrics can reveal hardware architectures. Servers MAY apply
"noise" (fuzzing) of approx $\pm$ 1% to reported values to mitigate
identification while maintaining audit accuracy.
5.4. Denial of Service (DoS)
Dynamic aggregation of metrics for custom period parameters can be
resource-intensive. Servers SHOULD rate-limit requests to the
sustainability URI and cache all generated reports.
6. IANA Considerations
IANA is requested to register the "sustainability" well-known URI in
the "Well-Known URIs" registry maintained at IANA
https://www.iana.org/assignments/well-known-uris
(https://www.iana.org/assignments/well-known-uris), following the
procedure outlined in [RFC8615].
* *URI Suffix*: sustainability
* *Change Controller*: IETF
* *Specification Document*: This Document
* *Status*: Permanent.
7. References
7.1. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997,
<https://www.rfc-editor.org/info/rfc2119>.
[RFC3339] Klyne, G. and C. Newman, "Date and Time on the Internet:
Timestamps", RFC 3339, DOI 10.17487/RFC3339, July 2002,
<https://www.rfc-editor.org/info/rfc3339>.
[RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
May 2017, <https://www.rfc-editor.org/info/rfc8174>.
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[RFC8259] Bray, T., Ed., "The JavaScript Object Notation (JSON) Data
Interchange Format", STD 90, RFC 8259,
DOI 10.17487/RFC8259, December 2017,
<https://www.rfc-editor.org/info/rfc8259>.
[RFC8615] Nottingham, M., "Well-Known Uniform Resource Identifiers
(URIs)", RFC 8615, DOI 10.17487/RFC8615, May 2019,
<https://www.rfc-editor.org/info/rfc8615>.
[RFC8949] Bormann, C. and P. Hoffman, "Concise Binary Object
Representation (CBOR)", STD 94, RFC 8949,
DOI 10.17487/RFC8949, December 2020,
<https://www.rfc-editor.org/info/rfc8949>.
7.2. Informative References
[GHG-PROTOCOL]
World Resources Institute and World Business Council for
Sustainable Development, "The Greenhouse Gas Protocol: A
Corporate Accounting and Reporting Standard (Revised
Edition)", 2004.
[GSF-SCI] Green Software Foundation, "Software Carbon Intensity
(SCI) Specification, v1.0", December 2022.
[EU-CSRD] European Parliament and Council, "Directive (EU) 2022/2464
as regards corporate sustainability reporting (CSRD)",
December 2022.
[UN-SDG] United Nations, "Transforming our world: the 2030 Agenda
for Sustainable Development", 2015.
[W3C-WSG] World Wide Web Consortium, "Web Sustainability Guidelines
(WSG) 1.0", 2023.
Author's Address
Andrei Nicolae BESLEAGA
Independent
Email: andrei.besleaga@ieee.org
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