This attribute indicates the approximate bit rate for the connection.
The bit rate is determined from the cell rate provisioned for the Vcc
linked to this connection. The cell rate is multiplied by 53 bytes per
cell and 8 bits per byte to obtain the bit rate. The ifSpeed of the
entry in the ifTable corresponding to the AtmMpe component is the
lowest speed of all the connections associated with the AtmMpe
component.