參考答案
An architect would know to use the direct connection when there is a need for guaranteed bandwidth, latency, and performance. With a direct connection, there are some things that happen along the way, but it's effectively like you have a wire between two different locations. The latency on the wire (how long it takes to go from both ends of the wire) doesn't change. Thus, if you've got a 10-gigabit link, you're going to always have 10 gigabits.
Simply put: the latency, performance, and bandwidth are consistent.
With a VPN, you connect to the internet on both sides, then you create a tunnel and encrypt your data over the internet. The internet is not private and that's why you have to encrypt your data. The advantages when you use a VPN are that it's typically cheaper because you're not buying a direct connection from two different locations; you're just connecting to the internet. Also, VPNs are simple to set up because you can create any connection to any place that has internet connectivity.
The disadvantage with a VPN is that internet bandwidth, latency, and performance are not guaranteed. Your internet service provider may guarantee you access to them, but once you get off their network and on the internet, there are no guarantees. Internet is basically best-effort delivery. In simple terms, if I try to reach a webpage, it doesn't mean it's going to get there. It should and It'll try, but it's not guaranteed. Performance on the internet can be all good, perfect, or horrible. Over a wire, if it takes 3 milliseconds, it's always going to do that. When you're dealing with the internet, because your speed is not guaranteed, your performance and your latency is not guaranteed either. You can run into variations in latency (called “jitter”). For example, if the first message takes 2 milliseconds, the second 100 milliseconds, and the third 5 milliseconds – message 2 is going to arrive long after message 3 and that may be a problem.