 M and N are what are often referred to as "bounded buffers", and have a fixed capacity in terms of the number of IPs that they can hold at any point in time.The concept of "ports" is what allows the same component to be used at more than one place in the network.In combination with a parametrization ability, called Initial Information Packets (IIPs), ports provide FBP with a component reuse ability, making FBP a component-based architecture.