Internet News Internet Investing Internet Technology Windows Internet Tech. And it looks like this happens mostly at the class 5 switch layer. So the switch fabric should probably be circuit or damned close. ATM CBR adds 6 ms. IP typically adds more than that, depending on how inefficient you want to be, and tends to have problems providing pure CBR service.
Some switches have both packet and circuit fabrics, which is probably the right answer.
The packets get involved for those who want to do packetized interswitch trunking, for instance, but stay out of the way of the local circuit calls.