2 Figure 1: Protocol analysis in Shared Ethernet: All data communication can be recorded. Protocol analysis in Switched Ethernet The development of the repeating hub into the switched hub (or switch for short) increased performance significantly. In contrast to hubs, switches are able to switch dedicated peer-to-peer connections between the individual connections. Switches which use the second layer (possibly an even higher layer) of the ISO/OSI reference model have an internal switching matrix. When the switch receives a data packet, it compares the target address with its internal address tables and switches a connection to the precise port at which the target station can be reached. Data are only forwarded to the intended receiver. The other ports remain free.In switch-based networks a network segment always consists of only two stations – the switch and the station connected to the port. The cable is available exclusively to the two stations and is thus always free and collisions cannot occur. Shared Ethernet became Switched Ethernet. Since collisions can no longer occur with this system, the CSMA/CD procedure is also no longer used. In addition, full-duplex operation (simultaneous sending and receiving of data) is possible. Switches have had a positive effect on load and performance but they make network analysis more difficult since the protocol analyzer– like every other station – also now only "sees" the Unicast frames which are forwarded to the port in addition to Multicast and Broadcast frames. And only these frames can be recorded by the protocol analyzer. Data communication which the switch passes on to other ports is no longer "visible" to the protocol analyzer.