A communication system that comprises at least two links to carry signals, a first communication unit and a second communication unit. The first communication unit comprises at least two ports, each port configured to transmit and receive signals; and a logic unit configured to process the signals transmitted and received by each of the at least two ports in the first communication unit. The second communication unit comprises at least two ports, each port configured to transmit and receive signals and coupled to a respective one of the at least two ports in the first communication unit via a respective one of the at least two links; a programmable logic unit configured to process the signals transmitted and received by each of the at least two ports in the second communication unit; and a processor. The processor is configured to detect a crossover connection between one of the at least two ports in the second communication unit and the respective one of the at least two ports in the first communication unit based on an analysis of a pair identifier field in a message received at the second communication unit, wherein the pair identifier field is separate from the address field of the received message.