OPEN and OPEN_ACK now carry proto:1 alongside upstream_id:1. The
session is tagged with its transport proto and reliability semantics
switch on the specific proto:
- TCP (proto=1): full L2 reliability (seq, ack, retransmit, in-order)
- UDP (proto=2, reserved): best-effort (no retransmit, no ordering,
no pure ACKs — seq/ack_seq fields present but ignored)
This is architecturally correct: instead of a generic 'reliable:bool'
flag, each proto gets the semantics it needs. Today only TCP exists so
every session is reliable, but the extension point is clean for when
stateless protos are added.
Updated: PROTOCOL.md, Rust frame.rs/session.rs/main.rs,
C# Frame.cs/SessionManager.cs.
DATA frames now carry seq:4 and ack_seq:4 in a 16-byte extended
header. Both sides maintain per-session send/recv state:
Sender:
- Monotonic seq counter, retransmit buffer (seq -> frame bytes)
- Retransmit timer: 5ms timeout, 10 max retries -> CLOSE
- Window advances on cumulative ACK
Receiver:
- In-order delivery to TCP socket (expected_seq)
- Out-of-order buffering (SortedList by seq)
- Duplicate detection (seq < expected -> discard + re-ACK)
- Pure ACK frames (empty-payload DATA) for duplicate/OOO responses
This prevents lost Ethernet frames from permanently corrupting TCP
sessions, which was the key v1 limitation. The local kernel TCP stack
ACKs data before we chunk it into DATA frames; without L2 reliability
a dropped frame creates an unrecoverable gap.
Version bumped to 2. Both sides must speak v2; no negotiation.
Updated: PROTOCOL.md (full v2 spec), README.md, Rust frame.rs/
session.rs/main.rs, C# Frame.cs/SessionManager.cs/TunnelLink.cs.
mute