Transport Layer¶

Status: Planned

All transport layer modules are in the design phase. Implementations will follow the same header-only, zero-allocation pattern as existing modules.

Overview¶

Transport layer protocols for reliable and unreliable data delivery. Focused on low-latency implementations suitable for trading systems, telemetry, and real-time control.

┌─────────────────────────────────────────────────────────────────────┐
│                         Application                                   │
├──────────────────┬──────────────────┬──────────────────────────────┤
│    TCP Stack     │  UDP Multicast   │          QUIC                 │
│  (State Machine) │  (Group Mgmt)    │      (0-RTT + TLS)           │
├──────────────────┼──────────────────┼──────────────────────────────┤
│   raw_socket /   │   raw_socket /   │     UDP + TLS 1.3            │
│   kernel TCP     │   kernel UDP     │                              │
├──────────────────┴──────────────────┴──────────────────────────────┤
│                    Network Layer (L2/L3)                             │
└─────────────────────────────────────────────────────────────────────┘

Modules¶

Module	Status	Description	Target Latency
TCP Stack	🔲 Planned	Userspace TCP state machine	< 10 µs handshake
UDP Multicast	🔲 Planned	IGMP group management, multicast send/recv	< 5 µs
QUIC	🔲 Planned	QUIC 0-RTT connection establishment	< 1 ms

Design Goals¶

Deterministic latency Bound worst-case times, avoid kernel scheduling jitter
Userspace-first Bypass kernel stack where possible (raw_socket + state machine)
Zero allocation in fast path Pre-allocate all buffers at startup
Integration with epoll reactor All sockets register as FDs in the event loop
Protocol correctness RFC-compliant state machines with exhaustive testing

Architecture Decisions¶

Decision	Rationale
Userspace TCP	Avoid kernel TCP's buffering, congestion control overhead
Kernel UDP multicast	IGMP handled by kernel; userspace for packet processing
QUIC over UDP	0-RTT reduces connection latency; built-in encryption
Pre-allocated buffers	Memory pool supplies all packet buffers

Dependencies¶

Module	Depends On
TCP Stack	raw_socket, epoll_reactor, ring_buffer
UDP Multicast	epoll_reactor, memory_pool
QUIC	UDP multicast, memory_pool, (TLS library)