bridge protocol data unit (BPDU)

The Bridge Protocol Data Unit (BPDU) is a protocol data unit for bridges or switches that uses the spanning tree protocol to exchange management information and control information between bridges in a network.

To determine the network topology and the location of bridges in the network, root bridges exchange BPDU frames with each other. Such a BPDU frame consists of several data fields.

Bridge Protocol Data Unit (BPDU) frame.

The first data field contains the destination address of the root bridge as seen by the sending bridge. This address field is followed by the Source Address( SA) data field, which is the address of the sending bridge and its port designation. The other data fields are the length field, which specifies the length of the BPDU frame, and the Destination Service Access Point( DSAP) and Source Service Access Point( SSAP) data fields. The data fields for the service access points are individual destination and source addresses or a merged group address of a MAC address. The Bridge Protocol Data Unit (BPDU) is completed by the configuration messages with important identification values for the corresponding route section.

Bridge Protocol Data Units are normally sent every two seconds. Receiving bridges use the configuration messages contained in the BPDUs to optimize routing. They also transmit this data to the connected local area networks( LAN).

Bridge Protocol Data Units (BPDU) are used for loop suppression in the network and for improving data traffic. If the protocol data units do not reach the communication partner, then there is a fault or interruption in the frequently used connection. The new path selection is then executed via the spanning tree protocol.