SIP trunking - part 1

Recently we implemented a Vodafone SIP trunk at our office. The Vodafone setup consists of a fiberswitch and a Cisco 2901 CUBE (Cisco Unified Border Element). Normally the CUBE connects directly to a Cisco Unified Communication Manager (CUCM) but we connected it to our own CUBE mainly because of 3 reasons:

• our own CUBE enables us to control the way it talks tot the CUCM
• we need SRST on the CUBE because the SIP-trunk is not located at the CUCM-site.
• it's also the prefered way to do it  

The first thing we had to think about is: how do we connect to our CUCM? SIP or H.323? We went for SIP, also because we wanted to stay as close to the suggested setup in the Vodafone-documentation.