Based on the Layer 2 switch function, The EPLAN realizes transmission of the accessed data based on destination media access control (MAC) address of the data.
The EPLAN services can be accessed from a minimum of two nodes. The services of different users do not need to share the bandwidth. That is, in the case of EPLAN services, a bandwidth is exclusively occupied by the service of a user and the services of different users are isolated. In addition, the extra QoS scheme and security scheme are not required. There are more than one node in the EPLAN services, Hence, the nodes need to learn the MAC addresses and forward data according to MAC addresses. Therefore, Layer 2 switching is involved. See Figure 1.
As shown in Figure 1, three branches of user F need to communicate with each other. On NE1, the IEEE 802.1d bridge is established to achieve EPLAN services. IEEE 802.1d bridge can create the MAC address-based forwarding table, which is periodically updated by using the self-learning function of the system. accessed data can be forwarded or broadcast within the domain of the IEEE 802.1d bridge according to the destination MAC addresses.
To avoid broadcast storm, the EPLAN services cannot be set as a ring. If the EPLAN services are set as a ring, the rapid spanning tree protocol (RSTP) must be started in the network.