Abstract: A telecommunications network with system for automatic detection of the topology of the network or of a sub-network thereof, comprises a plurality of network elements or nodes linked together to establish communications trails with termination points in ports of elements of the plurality of network elements. Each termination point is assigned a unique address in the network or in the sub-network and the corresponding network element sends along the outgoing trail from the termination point a message representing the unique address assigned and which is intended for the termination point at the other end of the trail. Each network element at either end of a communication trail therefore receives the message representing the address of the termination point of the element at the other end. In this way, each termination point of a connection will have received in the message the information that identifies the other termination point to which it is connected.