Connection Lifecycle

Overview

A QUIC connection progresses through well-defined states. Zoomies models each as events emitted fromQuicConnection.

Initial → Handshake → 1-RTT (application data) → Close

Handshake

The TLS 1.3 handshake runs inside QUIC CRYPTO frames. Zoomies handles:

1. Initial packets — Client Hello / Server Hello exchange
2. Handshake packets — Certificate, Finished messages
3. HandshakeComplete event — Keys derived, 1-RTT ready

events = conn.datagram_received(datagram, addr)
for event in events:
    if isinstance(event, HandshakeComplete):
        # Connection is ready for application data
        ...

Streams

QUIC multiplexes data over streams within a single connection. Each stream is independent — no head-of-line blocking.

# Open a stream and send data
stream_id = conn.get_next_stream_id()
conn.send_stream_data(stream_id, b"hello")

# Receive stream data via events
case StreamDataReceived(stream_id=sid, data=data, end_stream=fin):
    ...

Loss recovery

Zoomies implements RFC 9002:

• RTT estimation — EWMA smoothing of round-trip samples
• Packet-number loss detection — Mark lost after threshold
• Time-based loss detection — Timer-driven retransmission
• PTO probing — Probe Timeout with exponential backoff
• NewReno congestion control — cwnd gating in the send path

The recovery layer is integrated intoQuicConnection— no extra setup needed.

Close

Connections close viaCONNECTION_CLOSEframe or idle timeout.

case ConnectionClosed():
    # Clean up resources
    ...