|
An example of a managed Ethernet switch: The MCS Series carries sixteen 10/100 TX ports with a multimode fiber option. It handles control protocols such as Profinet, EtherNet/IP and Modbus TCP and provides message filtering, redundancy, and diagnostic LED readouts. |
It is often confused with an Ethernet hub. A hub is analogous to an extension cord. After boosting the signal level, it sends in-coming messages to all other devices to which it connects. An Ethernet switch, in contrast, manipulates incoming signals in a way that reduces network traffic before sending them out to other devices on the network.
Specifically, incoming data packets to an address that tells the destination of the message. The switch compares this information to addresses it has learned and holds in an internal look-up table. It uses this comparison to send the data packet only to the right port.
also eliminate the unpredictable timing delays inherent in hubs when they send Ethernet traffic to their ports.
There are two main kinds of : managed and unmanaged. Both do basic switching, but managed switches also perform extra tasks such as diagnostics, restricting network access for security reasons, or providing communications redundancy.
Managed switches can also be configured to filter out certain types of Ethernet packets so applications can run faster. Such functions tend to be most useful in high-speed (millisecond-level response) control or in large networks likely to expand in the future. To allow management of these added functions, managed switches need to be assigned their own IP addresses.
The price levels of industrial managed switches can typically range from $100 to $150/port. Unmanaged switches provide basic switching for $35 or less per port. They often serve as an inexpensive means of adding Ethernet devices to a network when there is no need for advanced switch functions. Because unmanaged switches don't have their own IP address, they cannot signal their status to other devices on the network. So they instead may be equipped with alarm contacts to generate a warning if power to the switch is lost. Unmanaged switches have a fixed number of ports, typically in the range of 5, 8, or 16 per device.
Phoenix Contact (phoenixcon.com) provided information for this article.