the operator this poses challenges since the network must reconfigure itself each time the train configuration is changed with the exception of the novel aspect to be described the network management system generally operates in a conventional manner using a configuration based on lonworks u2122 network technology developed by echelon corporation a suitable cbtc system is the seltrac u2122 system referred to above the network topology is an important part of the architecture because it permits the obcu 12 to identify which ciu 14 nodes are part of the same train unit via the nodes attributes namely a1 or a2 car left side or right side network the problem of identifying a ciu to a train unit arises because of multiple limitations in the architecture that must be circumvented the train unit identification id number which is assigned to a train unit cannot be transferred to all cius because in a cbtc system the train unit includes a monitoring diagnostic system md connected to the cius in the a2 car cius and not to the a1 using the cbtc network to transfer the information is not a valid option the a1 car needs a train unit id to find out in which train unit it is and to initialize the cbtc network the a2 car needs an initialized cbtc network to send the id of the train unit to the a1.