Since Session Initiation Protocol (SIP) was originally defined as a signaling protocol for multimedia sessions, SIP has grown beyond its targeted use as an IP-based telephony messaging medium to conferencing and instant messaging.   A service provider infrastructure focused on supporting IP-based telephony services is necessarily more complex than simple, web-based services. This makes ensuring reliable, scalable services more difficult.  This paper addresses the challenges and solutions when providing high-availability and scalability for SIP services.