In the last chapter, the characteristics of traffic grooming WDM networks with arbitrary topologies were studied from the perspective of blocking performance. It has been shown that the blocking performance is not only affected by the link traffic and the routing and wavelength assignment strategy, it is also affected by the arrival rates of different low-rate traffic streams, their respective holding times and more importantly, the capacity distribution of the wavelengths on the links. In such networks, call requests arrive randomly and can request for a low-rate traffic connection to be established between the source and the destination. Under dynamic traffic conditions, call requests that ask for capacity nearer to that of the full wavelength experience a higher probability of blocking than those that ask for a smaller fraction. In fact, the difference in blocking performance between the high- and low-capacity traffic streams becomes more significant as the traffic stream switching capability of the network increases. This difference in blocking performance for different capacities is directly affected by the routing and wavelength assignment policy that is used to route the call request. Hence, it is important that a call request is provided with its service in a fair manner commensurate with the capacity it requests. This capacity fairness is different from the fairness measure based on hop count that has traditionally been addressed in the literature.

In optical networks without wavelength conversion, due to the wavelength continuity constraint there is an increase in probability of a call request being blocked.