docs(openspec): archive complete frame transport

2026-08-10 08:54:36 +07:00
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 # gateway-media-framing Specification
 ## Purpose
 Define the versioned datagram framing, bounded reassembly, and explicit negotiation required to carry complete encoded media units.
 ## Requirements
 ### Requirement: Versioned complete encoded-frame datagrams
 The Protocol SHALL register `datagram-v2` with a 23-byte network-order header containing magic, version, channel, flags, sequence, timestamp, unsigned 16-bit fragment index, unsigned 16-bit fragment count, and unsigned 16-bit payload length. Media datagrams MUST remain at most 1,200 bytes with at most 1,177 payload bytes, and one sequence MUST represent exactly one complete encoded unit of at most 1,048,576 bytes and 891 fragments.
 #### Scenario: Bounded large encoded frame
 - **WHEN** an encoded media frame is larger than the datagram-v1 18,864-byte limit but no larger than 1,048,576 bytes
 - **THEN** datagram-v2 carries it under one sequence in at most 891 independently bounded fragments
 #### Scenario: Oversized encoded frame
 - **WHEN** a sender attempts more than 1,048,576 complete bytes or 891 fragments
 - **THEN** framing rejects the unit before sending or allocating proportional state
 ### Requirement: Bounded complete-frame reassembly
 Datagram-v2 reassembly SHALL retain at most four incomplete media units and only the bytes actually received, permit bounded fragment reorder and exact duplicate fragments, reject conflicting duplicates or inconsistent metadata, expire incomplete state after 250 milliseconds, and emit a payload only after every fragment is present exactly once.
 #### Scenario: Reordered frame completes
 - **WHEN** every valid fragment for one unit arrives out of order within the reassembly bounds
 - **THEN** the receiver emits exactly one byte-identical complete encoded frame with its original boundary
 #### Scenario: Malformed or stale reassembly
 - **WHEN** fragments conflict, metadata changes, an index or count is invalid, state exceeds four incomplete units, or a unit exceeds its timeout
 - **THEN** the receiver rejects or evicts that incomplete unit without proportional allocation or payload emission
 ### Requirement: Explicit framing negotiation
 `CapabilityProfile.framing` SHALL accept only registered `datagram-v1` or `datagram-v2` values. A peer MUST use datagram-v2 only after exact capability intersection and MUST NOT reinterpret datagram-v1 bytes as datagram-v2.
 #### Scenario: Independent datagram-v2 peers overlap
 - **WHEN** both peers advertise the registered datagram-v2 framing profile
 - **THEN** generated Go, Rust, and Swift validation and fixed conformance accept the profile
 #### Scenario: Unknown or downgraded framing
 - **WHEN** a peer advertises an unknown framing value or the peers advertise different versions
 - **THEN** capability validation or intersection rejects the session before media forwarding