Network Switch Bandwidth Calculator

Network oversubscription are the phenomenon that occurs when the total potential demand of all the ports of a network switch exceed the switch’s internal bandwidth capacity. While many person consider the total number of ports that a switch has when purchasing the switch, the number of ports that a switch have does not indicate the bandwidth capacity of that switch. Furthermore, any network switch have a finite internal bandwidth capacity.

Should the total demand for data from all of the switch’s ports exceeds the switch’s internal bandwidth capacity, the switch will experience a bottleneck. A network bottleneck occur when a switch is unable to process the data that enters the switch at the same rate as the data leave the switch through all of its ports. In order to calculate the potential demand on a switch, it is first necessary to determine the number of active port on the switch.

What Is Network Oversubscription

Because not all of the switch’s ports are active at the same time, it is only necessary to calculate the number of active ports during instances of high data traffic. Examples of high data traffic includes data being transfer in and out of NAS device or when users are streaming high-definition video. In addition to calculating the number of active ports during high data traffic periods, it is also necessary to account for protocol overhead and duplex communication.

Protocol overhead is data that is added to every packet of data that is transferred on a network, and duplex communication allow for data to be sent in both directions along a network, both of which can contribute to the total amount of data that a switch must send and recieve. The ratio of the total number of ports to the internal bandwidth capacity of a switch is referred to as an oversubscription ratio. If the oversubscription ratio of a switch is 1:1, people say the switch is a non-blocking switch.

A 1:1 oversubscription ratio mean that the internal bandwidth capacity of the switch is equal to the total potential demand of all of the switch’s ports. Most switch manufacturers creates switches with oversubscription ratios that is higher than 1:1, such as 8:1. This is done so that the switch can handle less data than the internal bandwidth capacity of the switch.

Furthermore, uplinks are the connections between one switch and another switch or a router. The uplink between switches can become the bottleneck in a network, especially if the uplink has a low internal bandwidth capacity. If the uplink between two switches is too small in relationship to the switch’s internal bandwidth capacity, the uplink will become congested when the switch is transferring large amounts of data, such as during data backup.

The oversubscription ratios between different networks can differ due to the type of data that the devices that is connected to the switch create. For example, Wi-Fi access points may create different type of data than virtual machines such as those that are set up in Proxmox labs. Thus, the oversubscription ratio of the switch that houses virtual machines will be different than the switch that houses access point for a Wi-Fi network.

Furthermore, in order to ensure that there is enough internal bandwidth for the switch to handle any potential increase in data demands, it is common for network engineers to introduce the concept of safety headroom. Safety headroom is a percentage of internal bandwidth that is reserved, such as 15%, to allow for increased data demands from the devices that are connected to the switch. Should the demands of the data on the network be more high than the switch’s internal bandwidth capacity, some action must be taken to reduce the demand on the network switch.

These solutions include reducing the number of active ports on the switch, increasing the capacity of the switch’s uplinks, or replacing the switch with a moddern model that has a higher internal bandwidth capacity. Whatever change are made to a network switch, ensure that there is enough margin within the switchs internal bandwidth to handle the demands of the network. You’ll need to make sure there is enough margin, because it’s easy to forget about the furnitures requirements.

If you dont plan ahead, you should of checked the capacity sooner.