While the common features found on switches are sufficient for the needs of most networks, switches designed for certain networks may provide extra features that are specific to the networks involved. In this chapter, we describe advanced features that may be found in a variety of switches, as well as specialized features found in switches designed for specific networking environments.
Given that they are providing the infrastructure for switching packets, switches can provide useful management data on traffic flows through your network. By collecting data from multiple switches, or by collecting data at the core switches, you can be provided with views of network traffic that are valuable for monitoring network performance and predicting the growth of traffic and the need for more capacity in your network.
As usual in the networking industry, there are multiple standards and methods for collecting data from switches. In Simple Network Management Protocol, we described one widely-used system called the Simple Network Management Protocol, which can be used to collect packet counts on ports, among other uses. However, while counting packets is useful and can provide valuable traffic graphs, sometimes you want further information on the traffic flowing through your network.
There have been two systems developed to provide information on traffic flows, called sFlow and Netflow. SFlow is a freely licensed specification ...