Optical or lambda exchanges have emerged to interconnect networks, providing dynamic switching capabilities on OSI layer 1 and layer 2. So far, the only inter-domain dynamics have occurred on layer 3, the IP layer. This new functionality in the data plane has consequences on the control plane. We explain this by comparing optical exchanges with current Internet exchanges. Descriptions of optical exchanges have appeared in the literature, but discussions about these exchanges have been hampered by a lack of common terminology. This paper defines a common terminology for exchanges. Discussion in the community revealed four different meaning for the term “open exchange”. We list them in this paper. We classify the different kind of exchanges based on the interactions between the domains at the control plane. We use these control models to distinguish between different types of interconnection points.