A table of topology information from each topology agent that sends out NMM topology messages, and that has been heard by the reporting topology agent. The number of entries is determined by the number of distinct topology messages received. A topology message is identified by a combination of the IP address and segment-identifier contained in the message, and the slot-port on which it is received. Entries in the table are created by reception of a 'new' NMM topology message. An entry is removed from the table after no messages are received from the corresponding topology agent in the required time interval. NOTE: there is an entry for the reporting agent with the values of slot and port set to zero.