SBC Cheatsheet:

Interoperability is the ability of a system or a product to work with other systems or products without special effort on the part of the customer. Internet Telephony Service Providers (ITSP) come in many different deployment forms with many different policies and utilizations of SIP. In addition, SIP itself is written in a manner that is open for interpretation and some 40+ RFCs in use, all with some form of interpretation. In the end, this can be very challenging for many deployments.