RFC‑Substrate‑Awareness — Substrate‑Aware Transport Services (SATS)

EIS‑Aligned Substrate Consciousness Layering for TAPS (RFC 8095 / RFC 8923) and HTTP (RFC 9110)#

RefId: turn0browsertab1

Identifier: TFAWG‑0001
Status: Draft
Category: Informational
Date: 2026‑07‑02

Abstract#

This RFC defines Substrate‑Aware Transport Services (SATS) — an extension framework that layers EIS substrate‑consciousness onto the IETF TAPS transport model (RFC 8095 / RFC 8923), with HTTP‑level field extensions aligned to RFC 9110.

SATS introduces:

• a substrate model (Layer 0–8)
• substrate metadata encoding (SCO)
• traversal semantics
• fidelity‑grade computation
• transport‑service extensions
• HTTP substrate fields and status codes
• IANA registry definitions

SATS enables applications, relays, and transport systems to express substrate‑layer intent, RTT budgets, ordering constraints, and relay negotiation in a structured, interoperable way.

1. Introduction#

Modern transport systems lack substrate awareness.
RFC 8923 defines transport services but does not provide:

• substrate‑layer signaling
• RTT‑budget semantics
• layer‑transition ordering
• relay negotiation
• fidelity‑graded reliability

SATS addresses these gaps by layering EIS substrate‑consciousness onto TAPS, enabling:

1. SATS Framework — unified substrate‑aware transport model
2. SCO (Substrate Context Object) — metadata container
3. IPR Negotiation — Inside‑Path Relay discovery
4. HTTP Extensions — substrate‑aware request/response fields

2. Conventions & Definitions#

RFC 2119 / RFC 8174 Keywords#

MUST, MUST NOT, SHOULD, SHOULD NOT, MAY.

Glossary#

• EIS — Enterprise Identity Substrate
• SATS — Substrate‑Aware Transport Services
• SCO — Substrate Context Object
• RTT‑Budget — advisory/soft/hard RTT constraints
• IPR — Inside‑Path Relay
• Traversal Vector — ordered list of substrate layers
• Fidelity Grade — composite reliability score

3. Motivation#

RFC 8923 lacks substrate‑layer semantics for:

• identity traversal
• RTT budgets
• reliability grading
• ordering constraints
• relay negotiation

SATS introduces two primary axes:

• RTT/Inside — substrate‑layer RTT semantics
• EIS Identity — enterprise identity traversal

Together they form the substrate‑aware extension to TAPS.

4. EIS Substrate Model (Layer 0–8)#

SATS defines nine substrate layers:

Traversal Semantics#

• Ascending — 0 → 8
• Descending — 8 → 0
• Lateral — same‑layer transitions
• Non‑Contiguous — e.g., 0 → 4 → 8

Canonical RTT Budgets#

Defined per layer.

Reliability / Ordering / Loss Tolerance#

Each layer defines minimum fidelity thresholds.

5. Substrate Metadata (SCO)#

SCO is encoded using:

• CBOR (RFC 8949)
• Structured Fields (RFC 8941)

SCO Structure#

• LayerToken
• Traversal Vector
• RTT‑Budget
• Fidelity Grade
• RelayHop list

Traversal Vector Construction Rules#

Vectors MUST:

• be ordered
• reflect actual layer transitions
• match transport‑service constraints

Fidelity Grade Formula#

[ F = W_{rtt} f_{rtt} + W_{loss} f_{loss} + W_{relay} f_{relay} + W_{order} f_{order} ]

Weights and factors defined in IANA registry.

6. Transport‑Service Extensions#

SATS extends RFC 8095 / RFC 8923 with four features:

1. sats‑rtt‑budget#

• advisory
• soft enforcement
• hard enforcement

2. Inside‑Path Relay Negotiation (IPR)#

Discovery via:

/.well-known/sats-relays

RelayHop structure defines:

• relay identity
• substrate layer
• fidelity grade

3. sats‑ordering‑contract#

Defines layer‑transition ordering constraints.

4. sats‑reliability#

Fidelity‑graded reliability with fallback/abort escalation.

7. HTTP‑Level Extensions (RFC 9110)#

Request Fields#

• Substrate-Layer
• Substrate-Context
• Substrate-RTT-Budget
• Substrate-Traversal
• Substrate-Domain

Response Fields#

Three substrate‑aware response headers.

Trailer Fields#

Two substrate trailers for HTTP/2 and HTTP/3.

Status Codes (560–564)#

Custom substrate‑aware error codes.

Media Type Parameter#

sats-layer + Accept-Substrate.

8. Examples#

Five annotated exchanges:

1. L0 bootstrap
2. L3 identity assertion with RTT budget
3. L6 semantic payload relay with trailer
4. Non‑contiguous 0→4→8 traversal
5. HTTP/2 push with substrate trailer

9. Security Considerations#

• SCO spoofing
• RTT exhaustion attacks
• IPR trust model
• header injection
• downgrade/strip attacks
• SCO privacy requirements

10. IANA Considerations#

Three registries:

1. HTTP Header Fields (11 entries)
2. Transport Error Codes (0x5A01–0x5A07)
3. Layer Profile Weights & Fidelity Thresholds

11–12. References#

Normative#

RFC 2119, 8174, 8095, 8923, 9110, 8941, 8949, 4648

Informative#

RFC 8303, 9112, 9113, 9114, 8922, TAPS‑ARCH