The recent Optus outage impacted a significant number of individuals and businesses, totaling 10 million people. Initially, the company attributed the failure to a fault in the “core network.” However, their latest statement suggests that a “network event” caused a “cascading failure.”
To understand the complexity of the internet and how carriers like Optus manage it, they utilize the concept of the “three layer network architecture.” This model divides the network into three layers.
The first layer is the access layer, which includes the devices individuals use to connect to the internet, such as routers, mobile towers, and customer equipment. This layer is what people interact with most frequently. It is not interconnected, meaning each device sits at the end of the network. Therefore, an outage in this layer would only affect the individual and their local neighborhood.
The second layer is the distribution layer, which connects the access layer to the core network. It serves as the interconnecting layer since the access layer regions are not directly connected to each other. The distribution layer consists of large switches in local exchange buildings and the cabling that joins them together and connects them to the core network. Its main purpose is to efficiently route data between access points. An outage in this layer could impact entire suburbs or geographic regions.
The third and final layer is the core layer, which is the central backbone of the entire network. It connects the distribution layers together and links telecommunication carrier networks with the global network. While physically similar to the distribution layer with switches and cables, the core layer is faster, contains more redundancy, and houses device and customer management systems. It primarily handles volume and speed by connecting data centers, servers, and the internet using large fiber optic cables. An outage in this layer affects the entire country, as seen in the recent Optus outage.
The reason for dividing the network into three layers is to address the challenge of keeping everyone connected as the network expands. In a small network, it may be possible to connect everyone directly, but as the network grows, this becomes impractical. The three-layer model provides a functional description of a typical carrier network, helping to understand where equipment and systems are located in the network.
The core layer is crucial in ensuring that access layer traffic to and from the internet or data centers is processed and distributed quickly and efficiently. It handles massive amounts of data on a daily basis.
Given the significance of the core layer in network operations, it becomes clear why a failure in this layer can impact a large number of people, as seen in the Optus outage.