Link failure means that the fiber link between a pair of nodes gets interrupted which causes all the traffic between the node pair totally disconnected. Because the fiber links between node pairs are generally widely exposed though buried under ground, it is often vulnerable to incur a failure due to some un-intentional digs. Thus, compared to other network failures, the link failure is often more common.

Node failure is less frequent than the link failure, which means the failure of a switch node. The failure can be caused by reasons such as power turnoff or a fire. Although less frequent, node failure is generally more serious than a link failure, which can totally isolate a community or a city that is connected through the node from communicating with other places beyond the community or the city. Thus, it is of very important to maintain the high relaibility of a switch node.

Shared risk link group (SRLG) failure is considered the most common network failure concept. As special cases, it can model link and node failures. It can also model more complicated network failure scenarios such as a subnetwork on some region that may incur high risk of disaster such as a region that has a high frequency of earthquake.

The last type of network failure is related to network control system. It is often more disastrous as the whole network will be out of control. Specifically, a network control system failure can disable the function of establishing a new service connection or releasing an expired connection if existing network services are luckily not affected. Therefore, it is also very important to ensure a highly reliable network control system.