So I think we have mixed questions here. Let me address the one I know. Each of the major exchanges has a DC in which they will rent space to a 3rd party that w

So I think we have mixed questions here. Let me address the one I know. Each of the major exchanges has a DC in which they will rent space to a 3rd party that will want to trade on the exchange. That market data feed and order execution use BGP & multicast (market data info is in multicast). Order execution can sometimes be a different link outbound. Please note I am generalizing details here sticking to mostly common items. So let’s say you are in the DC and your cage is right next to the Exchanges router so you cross connect is only 10m. So that is 50ns of latency in the path (assuming 10G SR on MM fiber). Your next competitor down from you is 20m away. So they are 100ns of latency. If you are an HFT, well. These people pay to dig through mountains to have the shorter path. What happened was this became a major issue oh, 20 years ago maybe? So what the exchange does is run the exact same length of cable to every drop off. So if you are 10m away and the longest run in the DC is 100m away then every cable run is 100m.