> Exactly. The switches buffer packets.

In most cases, you're right. The vast majority of switches use a sore-and-forward design (buffering), but when you get into latency-critical applications, another type of switch design is used, typically called a cross-bar switch.

http://www.researchgate.net/publication/220055485_A_low-late...

http://www.google.com/patents/US5339396

I think opinions vary on whether or not crossbar designs "buffer" but it mostly depends on how you define buffering. None the less, the low-latency crossbar designs try to eliminate the latency caused by buffering in the older but more common store-and-forward designs.

This is a valid point and I should have been more precise. But AFAICT all those interconnects are single duplex point-to-point links, and thus not subject to the CSMA issues of asymmetric collision detection detailed in the linked article.