RPC Layer

Authority: Navigation (Non-normative)
Purpose: Overview and navigation for RPC semantic layer.

RPC is a semantic layer carried inside SBP Message frames. It does not define framing, transport, or security—those are handled by SBP and the session layer (SBRP/SBDP).

Relationship to SBP

RPC envelopes are encoded in MessageFrame.data. Channel subjects determine envelope semantics: rpc for request/response, event for notifications. See envelope.md#subject-namespacing.

Delegation

This protocol delegates:

• Wire format: Inherits SBP frame structure (see sbp/wire-format.md)
• Ordering: Inherits SBP ordering guarantees (see sbp/behavior.md)

This protocol defines:

• Envelope format: See envelope.md
• Correlation: See behavior.md
• Subject namespacing: See envelope.md
• Error code range: Defines codes 1100-1199 for envelope errors.

Errors

RPC defines error codes in the 1100–1199 range. See envelope.md. It operates alongside:

• SBP protocol errors (1000–1099) — see sbp/errors.md
• Application errors (2000+) — defined per-method

See the canonical Error Code Registry for all assignments.

Documents

Document	Status
envelope.md	Normative
behavior.md	Normative
conformance.md	Supporting
streams.md	Reserved

Document Authority

Concern	Primary	Supporting
Envelope structure	envelope.md	—
Request/response semantics	behavior.md	—
Correlation	behavior.md	—
Test specification	conformance.md	—

Recommended Reading Order

1. index.md (this document)
2. envelope.md — wire format and validation
3. behavior.md — semantics and timeouts

Related ADRs

• ADR-006: RPC envelope
• ADR-010: RPC correlation (cid)