The use of colours to support diversity

Diversity is a way to prevent that different connections are affected by the same failure. As networks are constructed in different layers and are structured into separate levels, planning for diversity becomes difficult. In Telia´s network this has been efficiently solved by structuring the network with colours; the red core network is completely separate from the blue one. Each core network can then be optimised independently. This colouring concept is in the contribution presented in relation to the notion of shared risk link groups that has appeared in standardisation. SRLGs are proper to define diversity, but our judgement is that colours are needed for network structuring and to get simple routing rules. Therefore we want to see colours implemented in the control plane of an automatically switched optical network (ASON).