OverSIP is an async SIP proxy/server programmable in Ruby language. Some features of OverSIP are: - SIP transports: UDP, TCP, TLS and WebSocket. - Full IPv4 and IPv6 support. - RFC 3263: SIP DNS mechanism (NAPTR, SRV, A, AAAA) for failover and load balancing based on DNS. - RFC 5626: OverSIP is a perfect Outbound Edge Proxy, including an integrated STUN server. - Fully programmable in Ruby language (make SIP easy). - Fast and efficient: OverSIP core is coded in C language. OverSIP is build on top of EventMachine async library which follows the Reactor Design Pattern, allowing thousands of concurrent connections and requests in a never-blocking fashion.