Hello all, I've been trying to better understand the inner workings of the US phone network for some time now, and I think that I have come pretty far in that goal, but there is still one topic which I have been unable to figure out: how do the major IXCs exchange calls with each other for destination numbers using off-net FGD tandems. I understand that, for example, MCI can pick up a call directly from a customer, or from a PICed line at a ILEC FGD tandem, and then cart that call to the FGD tandem for the target LATA (or to a private interconnect with the destination carrier), moving through several switches along the way. What I'm trying to understand is how calls reach alternate FGD tandems (e.x. widevoice, teliax, intelliquent) when the call is being carried by a different IXC (e.x. AT&T). Right now, I could order a CLLI code, and assuming that I could get SS7 connections, put up a switch that would reachable by any other switch, but I would have no actual circuits on which I could accept calls. Must these alternate FGD tandem providers acquire trunking from every outbound provider for their service to be usable? Is there some kind of inter IXC transit service? I would appreciate any insight that you could provide. Thank you, Enzo Damato