Implements a fast, lock-free port allocator using a bit set (u64 buckets) over a configurable port range. Provides O(1) allocate/deallocate with random starting offset to reduce collision predictability. The `PortAllocator` is a self-contained, reusable component for any service needing ephemeral port assignment in a fixed range.

Provides a global, self-shrinking `Buffer` type backed by a lock-free `crossbeam::ArrayQueue` of pre-allocated `BytesMut` buffers. A background task monitors the ratio of idle-to-acquired buffers and reduces the pool when it detects sustained excess, preventing memory leaks under burst workloads. The buffer is safely acquired/returned via RAII (Drop). This pattern is extraction-ready for any high-throughput network service.

Implements an in-memory switch that maps session `Identifier`s to `tokio::sync::mpsc::UnboundedSender` channels. Relay packets are published via `send()` which drops silently if the receiver is gone, providing backpressure-free forwarding. The switch is transport-agnostic and enables the cross-protocol (UDP↔TCP) relaying required by the TURN spec.

Defines a type-safe, extensible STUN/TURN attribute hierarchy using the `Attribute` trait. Each attribute (e.g., `UserName`, `XorMappedAddress`, `MessageIntegrity`) has a well-defined serialization/deserialization and is automatically discovered from the binary stream. The pattern supports both comprehension-required and optional attributes with zero-copy parsing, and can serve as a template for any TLV-based protocol codec.

Provides cryptographic primitives for STUN/TURN authentication: HMAC-SHA1 for MESSAGE-INTEGRITY, CRC32 fingerprint, and password derivation (MD5 and SHA256) per RFC 5389/8489. The functions are pure, side-effect-free, and come with verified test vectors; they can be extracted into a standalone crate for any STUN-based project.