フリー問題

問題文

Which capability is central to a software-defined networking controller?

選択肢

1. It stores the images from which virtual machines are created, so a network that runs no virtual machines at all leaves the controller with nothing to do.
2. It terminates the tunnels that carry tenant traffic.
3. It runs the routing protocols on each device in turn so that each device independently reaches its own conclusion about the best path, and it then compares those conclusions with each other and reports any disagreement it finds to the operator for resolution.
4. It maintains a view of the whole topology and, from that view, computes and installs the forwarding state that each device should use.