From a leading expert on the topic of SIP, "Session Initiation Protocol (SIP)" provides you with a comprehensive implementation guide to maintaining and troubleshooting an SIP network and understanding its operations. SIP is a signaling protocol used for VoIP, instant messaging, online games, and other multimedia elements. This practical guide covers registration procedures within an SIP network, security, SIP Response Codes, extending SIP to support new functions, and more.