NkSIP

Implements all SIP methods like INVITE, REGISTER, and OPTIONS as UAC, UAS, or Proxy, enabling versatile server applications such as proxies and B2BUAs.

Supports UDP, TCP, TLS, SCTP, WS, and WSS transports, handling thousands of simultaneous sessions and automatically utilizing all processor cores for high performance, as noted with 3,000+ call cycles per second.

Features a low-overhead plugin mechanism for adding functionality like authentication and event handling without modifying the core, reducing development overhead.

Allows on-the-fly configuration, code upgrades, and behavior changes without downtime, leveraging Erlang's runtime for zero-duration maintenance.