Its sip... you learn to expect the unexpected. I have personally seen some of the dumbest things possible in SIP with various phones.
/b
I've been watching FS (and Asterisk) for the past 3 years and if there's anything I've learned it's that SIP is a fickle friend. Saying that something is "the most SIP compliant" device/endpoint/gadget isn't exactly a bragging point. If every piece of SIP equipment out there tried to adhere to the absolute letter of every SIP-related RFC then nothing would work! (Yes, that's an exaggeration, but not a big one.) Anyway, we're all stuck with SIP because no one could come up with anything better *and* get enough telecom players to use it widely. So instead we're all stuck with a grossly imperfect protocol that has its strengths and weaknesses. The FS devs have chosen a wise course: make their SIP implementation use the good stuff in SIP while trying to minimize the stupid things that SIP allows and/or requires. End of rant, thanks for listening. -MC