A logical topology describes how devices seem to the user to be connected. In a shared Ethernet network that employs hubs rather than switches, for example, the logical topology seems to be that each node is connected to a common bus that flows from node to node. However, in reality, each device has its own private connection to the network, which allows it to communicate directly with other devices on the network. In general, a logical topology is any set of connections between nodes that appear as a single unit to the user. For example, in a shared hub network, the logical topology appears to be one large loop when looked at from an external point of view; however, each device has a direct link to the next, so they all function correctly even if some nodes fail. Logical topologies can also include physical links such as cables or wireless connections that do not share bandwidth. For example, two devices may have connectivity over a single cable but still be able to communicate with other devices over a different cable because they use separate frequencies.