The Internet is emerging as the new universal telecommunication medium. IP over WDM has been envisioned as one of the most attractive architectures for the new Internet. Consequently survivability is a crucial concern in designing IP over WDM networks. This paper presents a survey of the survivability mechanisms for IP over WDM networks and thus is intended to provide a summary of what has been done in this area and help further research. A number of optical layer protection techniques have been discussed. They are examined from the point of view of cost, complexity, and application. Survivability techniques are being made available at multiple layers of the network. This paper also studies the recovery features of each network layer and explains the impact of interaction between layers on survivability. The advantages and issues of multi-layer survivability have been identified. The main idea is that the optical layer can provide fast protection while the higher layers can provide intelligent restoration. With this idea in mind, a new scheme of carrying IP over WDM using MPLS or Multi Protocol Lambda-Switching has been discussed. Finally, an architecture is suggested by means of which the optical layer can perform an automatic protection switch, with priority considerations with the help of signaling from the higher layers.

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