s the cause of the fact that the number of channels that can be routed in an OChSPring depends on the traffic pattern: the more the sharing can be done the more the channels can be routed. In particular, the worst case happens when pure hub traffic is routed, where the situation coincides with that of an optical channel dedicated protection ring (OChDPring): the number of routed channels is equal to the number of wavelengths. This is due to the fact that, in case of hub traffic, all the channels are ter- minated on the same node (the hub) and all are topologically superimposed at least for a single link, SO that sharing is impossible. When a uniform traffic is loaded onto the OChSPring, since this means that OChs con- nects only contiguous nodes, the maximum sharing is possible since all the channels are either topologically or spectrally separated. This is the case in which the maximum num- ber of channels can be routed in the ring: this number is simply evaluated to be equal to (nm)/2 where n is the number of nodes (at least 3 to be a ring) and m the number of wavelengths. In all other cases, generic traffic patterns determine a maximum number of routable channels that is comprised between m (the number of wavelengths) and (nm)/2. Also shared OMS protection can be applied to optical ring, in strict analogy with what is done in SDH/SONET simply substituting wavelengths to time slots. However, in the OTN rings, OMS protection is less used with respect to OCh protection, due to the need of protecting the optical transmitters. Thus, we will not detail optical multiplex section shared protection ring (OMSSPring) architecture being a simple extension of the SDH/ SONET case. Also the coordination protocols that bring all the information needed to perform cor- rectly automatic protection switching are analogous in principles and implementation to the protocols for SDH/SONET and we will not repeat here in detail the analysis of their working. The only important point to consider is that both the OMS and the OTS headers 