We at Sipwise implement VoIP switches at major ISPs in Europe, and the most uncomfortable question, which is ALWAYS asked (mostly just as a side-question, like

We at Sipwise implement VoIP switches at major ISPs in Europe, and the most uncomfortable question, which is ALWAYS asked (mostly just as a side-question, like "Btw, I suppose you support it anyways, so how does your solution work in that regards?") is the one of lawful interception. There's a specification defined by the PacketCable consortium (http://www.cablelabs.com/packetcable/downloads/specs/PKT-SP-ES-DCI-I01-060914.pdf http://www.cablelabs.com/packetcable/downloads/specs/PKT-SP-...), and I'd say that almost every major vendor has implemented it in one way or the other in order to be deployed at cable ISPs.