Sideband Direct Protocol (SBDP)

Authority: Navigation (Non-normative)
Purpose: Overview and future roadmap for direct P2P sessions.
Status: Stub — This protocol is not yet specified.

SBDP is the planned direct (peer-to-peer) session protocol for Sideband. It will provide secure SBP transport without a relay, using mutual-authenticated session negotiation (ADR-015) over direct transports such as WebRTC DataChannel, QUIC, or TCP.

Status

SBDP is intentionally not specified yet to avoid premature abstraction. The current architecture ensures SBDP can be added without changes to SBP or higher layers.

Relationship to Other Protocols

Protocol	Role
SBP	Application framing (used unchanged)
SBRP	Relay-based secure session
SBDP	Direct secure session (this protocol)

Delegation

This protocol delegates:

• Wire format: Inherits SBP frame structure (see sbp/wire-format.md)
• Error codes: Reuses SBP error semantics (see sbp/errors.md)
• Ordering: Inherits SBP ordering guarantees (see sbp/behavior.md)

This protocol will define:

• P2P session establishment: Direct connection setup
• Noise XX session negotiation: Mutual authentication and key derivation
• NAT traversal: ICE/STUN/TURN or similar

Design Principles (Preview)

• No relay dependency
• Secure session establishment (Noise XX per ADR-015)
• Reuse SBP framing unchanged
• Pluggable transport (WebRTC, raw UDP, etc.)

Document Authority

Concern	Primary	Supporting
All	Not yet specified	—

Related Documents

• Protocol Architecture: Layer stack, wrapping rules
• SBP Specification: Application framing (will be used unchanged)
• SBRP Specification: Reference implementation for session layer

No normative specification exists at this time.