If you want to read an absolutely brilliant discussion of a key technical/security/policy issue around SIP in general and SIP trunking in particular, check out this VOIPSA blog post by Dan York.
If you want to read an absolutely brilliant discussion of a key technical/security/policy issue around SIP in general and SIP trunking in particular, check out this VOIPSA blog post by Dan York.Dan does a terrific job starting with what appeared to be a simple hack of Caller ID in SIP, then explaining technically what's going on, and then illustrating the larger issues that this particular exploit reveals. The bottom line is that, in a world of SIP trunks, there are new issues about where trust boundaries start and end, and which side of that demarc an end customer ought to be on.
In the old days, regulations made the demarc point very clear, and everyone knew on which side of it they stood, and what that implied about the services they would and wouldn't receive, and the measures they needed to take on their own behalf.
Today, it's a completely different story, and so in addition to worrying about availability and interoperability when it comes to SIP trunks, you'll also need to know the kind of details that Dan writes about. Definitely go read the whole post.
