Networks that use earlier technologies, and that almost any organization using networks for more than a year or so will have in operation. The major problem facing those with one or possibly several legacy networks is in trying to decide whether to design a new network so as to interwork with the legacy network, or to replace the legacy network at the same time as installing the new network. The interworking option will increase the complexity of the new network and tend to reduce its functionality. The replacement option will increase the overall cost of the new network.